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Positron-emission tomography/computed tomography (PET/CT) in the head and neck region is susceptible to artifacts caused by dental restorations. Metal artifact reduction is an established technology that can be used to improve the quality of CT images. The diagnostic efficacy of single-energy metal artifact reduction (SEMAR) for head and neck cancer has not been proven. We aimed to investigate the efficacy of SEMAR with PET/CT in the field of head and neck cancer. The study included 46 patients who underwent PET/CT with SEMAR. For qualitative evaluation, images with and without SEMAR were visually evaluated by two radiologists using a 5-point scale. For quantitative assessment, the standardized uptake values (SUVs) -related parameters were assessed based on their position in normal structures such as the tongue, tonsils, masseter muscles, and spinal cord. The qualitative analysis revealed that SEMAR improved the overall quality of PET/CT fusion images (2.28 ± 1.24 points vs. 3.61 ± 0.77 points, p < 0.0001). The scores for normal structures were also enhanced. SEMAR did not change the SUV-related values significantly. In conclusion, SEMAR significantly improved the quality of PET/CT fusion images. Thus, SEMAR with PET/CT clearly has potential diagnostic efficacy.

A man in his 60s with severe trismus was referred to our hospital. Based on computed tomography (CT), positron emission tomography/computed tomography (PET/CT), and biopsy, his initial diagnosis at another hospital was oropharyngeal cancer with cervical lymph node and distant metastases. After the review of the contrast-enhanced CT and reevaluated PET/CT images, we updated his diagnosis to left primary lung cancer that had metastasized to the cervical lymph nodes, bones, and skeletal muscles including the right medial pterygoid muscle. Since metastasis from primary lung cancer to the contralateral cervical lymph node is relatively rare, cervical lymph node metastases were thought to have originated from the metastatic lesion in the right medial pterygoid muscle. As metastases in the masticator muscles from lung cancer are rare, it is sometimes necessary to differentiate from primary head and neck lesions. Here, we report a rare case of lung cancer with the onset of trismus due to metastasis to the masticator muscle and perineural spread along the mandibular nerve.

The aim of this study was to investigate the diagnostic performance of whole-body [C]acetate PET/CT in less aggressive or indolent lymphomas, wherein [F]FDG PET/CT would exhibit limited sensitivity.Between September 2016 and May 2018, we prospectively evaluated 17 patients (9 men, 8 women; mean age [range], 71 [45-87] years) with pathologically proven less aggressive or indolent lymphomas according to Non-Hodgkin's Lymphoma Classification Project, using both [F]FDG PET/CT and [C]acetate PET/CT (performed on the same day). Detected nodal lesions were recorded according to the Ann Arbor classification. Extranodal (EN) lesions were also evaluated. We compared whole-body lesion detection between [F] FDG PET/CT and [C]acetate PET/CT using the McNemar test.In all patients, significantly more nodal and EN lesions were detected using [C]acetate PET/CT than [F]FDG PET/CT (nodal: 84 vs 64 regions; P0.001; EN: 26 vs 19 regions, P = 0.039). Bone lesions were detected in 8 and 5 patients using [C]acetate PET/CT and [F]FDG PET/CT, respectively (P = 0.25). Among the 14 patients (82.4%) who underwent bone marrow biopsy, bone marrow involvement was detected with sensitivities of 100% (6/6 patients) and 80% (5/6 patients) using [C]acetate PET/CT and [F]FDG PET/CT, respectively. Multiple areas of focal uptake in the spleen of 1 patient were exhibited on [F]FDG PET/CT but not [C]acetate PET/CT.[C]acetate PET/CT exhibited greater sensitivity than [F]FDG PET/CT for lesion detection in patients with less aggressive or indolent lymphomas, thus promising applicability as a physiological tracer in the study of such lesions.

Background [F-18]fluorodeoxyglucose positron emission tomography/computed tomography is routinely used for assessing Takayasu arteritis patients. However, extra-vessel [F-18]fluorodeoxyglucose uptake has not been evaluated in detail in these patients. We aimed to describe the extent and distribution of extra-vascular [F-18]fluorodeoxyglucose uptake on positron emission tomography/computed tomography in Takayasu arteritis patients. Seventy-three [F-18]fluorodeoxyglucose positron emission tomography/computed tomography scans from 64 consecutive Takayasu arteritis patients (59 women, mean age, 35.4 years; range, 13 to 71 years) and 40 scans from age-matched controls (36 women, mean age, 37.8 years; range, 13 to 70 years) were examined. We graded [F-18]fluorodeoxyglucose uptake in large vessels using a 4-point scale and evaluated extra-vessel findings. Factors correlated with disease activity were examined. We evaluated the relationship between disease activity according to the National Institutes of Health score with extra-vessel findings, as well as other inflammatory markers (e.g., white blood cell count and C-reactive protein level). Results Extra-vessel involvement was present in 50 of 73 (68.4%) scans, specifically at the following sites: lymph nodes, 1.4%; thyroid glands, 17.8%; thymus, 11.0%; spleen, 1.4%; vertebrae, 45.2%; and pelvic bones, 9.6%. Takayasu arteritis patients had higher [F-18]fluorodeoxyglucose uptake in the spine (P = 0.03) and thyroid glands (P = 0.003) than did controls; uptake in other regions was comparable between groups. Compared with inactive patients, those with active Takayasu arteritis had a higher number of [F-18]fluorodeoxyglucose uptake sites in the vasculature (P = 0.001). Finally, patients with a National Institutes of Health score of ≥ 1 had significantly higher extra-vascular involvement (P = 0.008). Conclusions Extra-vessel [F-18]fluorodeoxyglucose uptake may be present in the context of Takayasu arteritis-related inflammatory processes. Information on extra-vascular [F-18]fluorodeoxyglucose uptake may be useful for detecting and evaluating inflammatory processes when interpreting positron emission tomography/computed tomography scans obtained from Takayasu arteritis patients.

Grignard reagents (R2MgBr; R2 = Me, p-tolyl) regioselectively attacked the α-carbon of the bridgehead double bond of methyl- and benzylazafulleroids (only R2 = Me) in contrast to the β-carbon attac...

Oxidation of azafulleroids with peracids regenerated C60 depending on the N-substituents. Alkyl-substituted azafulleroids preferred the oxidation of nitrogen to afford N-oxides as possible intermediates for C60 in moderate yields. Phenyl- and tosyl-substituted azafulleroids rather allowed the oxidation at the carbon cage. Theoretical calculations predicted the order of reactivity of azafulleroids as well as the relative N/C nucleophilicity.

Nanocomposite films of polystyrene (PS) and poly(methyl methacrylate) (PMMA) were prepared by loading four variations of fullerenes such as pristine C60, multiarylated [60]fullerenes with tolyl (tolyl-C60) and phenol groups (phenol-C60), and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). The TGA analysis showed no appreciable change in their thermal and thermo-oxidative stabilities for PS/tolyl-C60 and PS/phenol-C60 films, but significant improvement up to +45°C for PS/C60 and PS/PCBM films even under air. The thermo-oxidative stability of PMMA/phenol-C60 and PMMA/PCBM, however, exhibited slightly larger improvements over that of PMMA/C60. We believe that the radical-scavenging ability of π-conjugative fullerenes and the dispersibility of fullerene–polymer combinations play key roles in these enhancements. We also found that optimal loading occurred at a relatively low content of fullerenes (0.4–0.8 wt%) probably because larger amounts may interfere with the morphological interaction of polymer chains which is essential for the thermal persistency of polymer. POLYM. COMPOS., 2014. © 2014 Society of Plastics Engineers

Azafulleroid, amino-bridged [5,6]-open fullerene, has the ambident N/C basicity of the incorporated enamine moiety. Acid-catalyzed arylation of N-substituted azafulleroids proceeded via two types of initial N/C protonation to perform monoarylation or 1,4-bisarylation for the N-alkyl substituents and shuttlecock-type pentakisarylation for the N-phenyl substituent. The dramatic product change was explained by considering the possible mechanism as well as the DFT computational results.

We studied the kinetics of the Diels-Alder reaction of Li(+)-encapsulated [60]fullerene with 1,3-cyclohexadiene and characterized the obtained product, [Li(+)@C60(C6H8)](PF6(-)). Compared with empty C60, Li(+)@C60 reacted 2400-fold faster at 303 K, a rate enhancement that corresponds to lowering the activation energy by 24.2 kJ mol(-1). The enhanced Diels-Alder reaction rate was well explained by DFT calculation at the M06-2X/6-31G(d) level of theory considering the reactant complex with dispersion corrections. The calculated activation energies for empty C60 and Li(+)@C60 (65.2 and 43.6 kJ mol(-1), respectively) agreed fairly well with the experimentally obtained values (67.4 and 44.0 kJ mol(-1), respectively). According to the calculation, the lowering of the transition state energy by Li(+) encapsulation was associated with stabilization of the reactant complex (by 14.1 kJ mol(-1)) and the [4 + 2] product (by 5.9 kJ mol(-1)) through favorable frontier molecular orbital interactions. The encapsulated Li(+) ion catalyzed the Diels-Alder reaction by lowering the LUMO of Li(+)@C60. This is the first detailed report on the kinetics of a Diels-Alder reaction catalyzed by an encapsulated Lewis acid catalyst rather than one coordinated to a heteroatom in the dienophile.

We have recently developed a facile synthetic method for highly water-soluble fullerene, so-called fullerenol, for the treatment of fullerene with hydrogen peroxide. This method was applied to fullerene soot to yield the corresponding new hydrophilic carbon materials, and the obtained products were subjected to infrared spectroscopy and elemental analysis. The DLS particle size analysis demonstrated the relatively high dispersion of hydrophilic fullerene soot with a diameter of ˜70 nm in water, while the hydrophilic activated carbon obtained by the same treatment showed the larger aggregation with diameters of 200 and 970 nm. The surface analysis using FE-SEM showed the difference in morphology between fullerene soot and activated carbon as well as between before and after hydrophilic treatment of the soot with hydrogen peroxide. Moreover, this hydrophilic fullerene soot exhibited high antioxidant activity (%AOA) up to 87% compared with fullerenol C60(OH)36 (54%) and C60 (50%) evaluated by β-carotene blea...

We report the growth of Cu2O thin films on glass and MgO(100) substrates by molecular beam epitaxy. Crystal orientation of Cu2O thin films on glass substrate were changed from (100) to (111) with increasing the deposition rate. The Cu2O thin films were epitaxially grown on MgO(100) substrate with an orientation relationship of Cu2O(110) // MgO(100). The film quality and electrical properties of Cu2O thin films were changed with deposition rate. The slow deposition rate resulted in high conductivity and mobility, as well as good crystallinity and orientation.

Acetalized [60]fullerenes were synthesized from cyclohexanone-fused [60]fullerene, which was facilely prepared by Diels–Alder reaction of C 60 with silylether diene, on treatment of various aliphatic alcohols under TiCl 4 catalyst. The spiro-cyclic acetalized [60]fullerenes having five, six, and seven-membered rings were also synthesized by using the corresponding diols under the same condition. The slightly raised reduction potentials E red (∼0.04 V) relative to those of PCBM were observed by cyclic voltammetry measurement, depending on the identity of alkyl group/chain. The noncyclic acetalized [60]fullerenes showed lower thermal stability up to 200 °C, while the cyclic ones exhibited the drastically improved thermal stability up to 350 °C under nitrogen atmosphere. The acid-catalyzed hydrolysis easily removed the acetal moiety quantitatively, resulting in a considerable change of solvent solubility of the fullerene.

Grignard reagents (RMgBr: R = Et, p-tolyl) selectively attacked the β-position of the bridgehead double bond of tosylazafulleroid through interaction of Mg with the S[double bond, length as m-dash]O group. The following [5,6] ring closure and C-N bond scission led to aryl/alkyl aminylfullerenes with 1,2-configuration. Tolyl-substituted aminylfullerene was further converted into 1,4-di(p-tolyl)fullerene on treatment in acidic toluene.

The therapeutic effects of fullerene derivatives on many models of inflammatory disease have been demonstrated. The anti-inflammatory mechanisms of these nanoparticles remain to be elucidated, though their beneficial roles in allergy and autoimmune diseases suggest their suppressive potential in acquired immunity. Here, we evaluated the effects of C60 pyrrolidine tris-acid (C60-P) and polyhydroxylated fullerene (C60(OH)36) on the acquired immune response in vitro and in vivo. In vitro, both C60 derivatives had dose-dependent suppressive effects on T cell receptor-mediated activation of T cells and antibody production by B cells under anti-CD40/IL-4 stimulation, similar to the actions of the antioxidant N-acetylcysteine. In addition, C60-P suppressed ovalbumin-specific antibody production and ovalbumin-specific T cell responses in vivo, although T cell-independent antibodies responses were not affected by C60-P. Together, our data suggest that fullerene derivatives can suppress acquired immune responses that require T cells.

Variously substituted [6,6]closed aziridinofullerenes were exclusively obtained from acid-catalyzed denitrogenation of triazolinofullerenes without formation of relevant [5,6]open azafulleroids, which are the major products on noncatalyzed denitrogenation. The mechanistic consideration by DFT calculations suggested a reaction sequence involving initial pre-equilibrium protonation of the triazoline N(1) atom, generation of aminofullerenyl cation by nitrogen-extrusion, and final aziridination.

A lithium-encapsulated fullerenol Li@C60(OH)18, as an example of a polar solvent-soluble endohedral fullerene derivative, has been synthesized and fully characterized by infrared spectroscopy, nuclear magnetic resonance spectroscopy, UV spectroscopy, electron spin resonance (ESR) spectroscopy, matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS), elemental analysis, thermogravimetric analysis, and inductively coupled plasma-atomic emission spectroscopy (ICP-AES), and the particle size was determined using the induced grating (IG) method, and scanning probe microscopy. The encapsulated Li+ was clearly detected by 7Li NMR at very high field in the range −15 to −19 ppm, an intermediate lithium-encapsulated fullerenol was detected by MALDI-TOF-MS, and the molar ratio of lithium-encapsulated fullerenol to empty fullerenol was quantitatively determined to be 12:88 by ICP-AES. The solid-state ESR and particle size measurements using the IG method showed the characteristic anionic behavior with no external counter cations, in what can be called a “cation-encapsulated anion nanoparticle”, revealing the drastic differences between its properties and those of empty C60(OH)16. Open image in new window

The mCPBA oxidation of methano-bridged [5,6] open fulleroid 1 anomalously resulted in the selective electrophilic addition at the bridgehead anti-Bredt double bond rather than the usual epoxidation. The mechanistic preference for the unprecedented stepwise addition of mCPBA vs the concerted epoxidation was explained in terms of the notable π-orbital misalignment (>30°) based on the B3LYP/6-31G(d) level calculation.

CF3SO3H-catalyzed reaction of 5-alkyl-(R)-substituted diphenylhomobenzoquinone epoxides (R = Me, iPr, tBu) provided indenoquinones, a cyclopenta[b]chromene-2-carbaldehyde, and furan-3(2H)-ones through novel cationic domino rearrangements depending on the R substituents. The mechanisms of these reactions were described by a combination of various key steps involving (i) transannular cyclization of the endo-phenyl group, (ii) epoxide and cyclopropane ring opening, (iii) ring contraction of the original quinone frame, (iv) dehydration and intramolecular SE2/SN2-Ar cyclization, as well as (v) possible pseudopericyclic cheletropic decarbonylation.

A kinetic study of Diels–Alder (DA) reactions of some fullerene dienophiles, i.e. C60, [R1, R2]-substituted fulleroids 1 (a: [H, H], b: [H, CN], c: [H, CO2Et]; d: [H, Ph], e: [Ph, Ph]) and [H, H]-substituted methanofullerene (2), with various dienes [cyclopentadiene (3a), 9-methylanthracene (3b), 1,3-cyclohexadiene (3c), 2,3-dimethylbutadiene (3d) and 2-methylbutadiene (3e)] has been carried out in toluene at 30 °C. Notably, the relative rate ratio k/k0 for each dienophile (vs. C60) was remarkably dependent on the diene used; the less hindered H/CN fulleroids 1a and 1b became 25–104 times more reactive than C60 with conformationally flexible dienes such as 3d and 3e. These fulleroids, however, showed similar or rather diminished reactivity with rigid 3a and 3b. In contrast, slightly hindered 1c exhibited a three to seven times reduced rate of reaction for 3d–e, and more hindered 1d–e and the 58-π-conjugated 2 displayed reduced reactivity with almost all the dienes. Based on product analysis, the enhanced reactivity was ascribed to the exclusive addition at the highly strained bridgehead double bond of the transannular [5,6] open ring orifice. It was concluded that the twisted anti-Bredt double bond can perform a topologically suitable [π2s + π4s] orbital interaction with the less congested, labile dienes. Such an orbital interaction is inhibited for both the congested fulleroids and the rigid dienes, which displayed alternative addition at a less twisted double bond.

Novel nanocomposite films of polycarbonate (PC) with fullerene derivatives, such as pristine fullerene C60 and polyhydroxylated-fullerenes, C60(OH)12 and C60(OH)36, were prepared. The optical, thermal, and mechanical properties of the composites were measured. Nanocomposite films of poly (vinyl alcohol) (PVA) with C60(OH)36 were prepared as a reference to show how improved dispersion of the nanofiller affects the overall transparency of the composites. Ultraviolet-visible spectroscopy showed that the addition of hydroxylated fullerenes did not affect visible light transmittance of the films significantly in the range of 400–800 nm. Differential scanning calorimetry (DSC) and thermo–gravimetric analysis (TGA) measurements showed the increased thermal stability of PC/C60(OH)12 film as compared to pristine PC film. This phenomenon was explained by the rigid polymer interphase regions formed around C60(OH)12 due to the plausible hydrogen bonding and hydrophobic interaction. On the other hand, the lower thermal stability of PC–C60(OH)36 was assumed to be caused by large agglomeration of the C60(OH)36 particles and the partial hydrolysis of the polycarbonate matrix. Tensile testing of the composites showed reduction in elongation at break and yield tensile strength. These results may be caused by the particle agglomerations which act as the initiation points for cracks.

Novel single electron transfer (SET) reaction of dienamine with C60 is presented. The generated dienamine radical cation underwent a 1,6-hydrogen shift followed by a radical–ion coupling with a C60...

Triazoliumfullerene was first prepared by the [3+2] cycloaddition of in situ generated 1,3-diaza-2-azoniaallene with fullerene and was characterized by the dispersed positive charge over the fullerene sphere associated with periconjugation. This new type of amphiphilic fullerene tended to form vesicles and crystalline aggregates after the casting of THF or MeOH solutions.

A water-soluble polyhydroxylated fullerene, i.e. a fullerenol, with 44 hydroxyl groups and 8 secondary bound water molecules, C60(OH)44·8H2O (estimated average structure), has been synthesized in a facile one step reaction from pristine C60 by hydroxylation with hydrogen peroxide in the presence of a phase-transfer catalyst, tetra-n-butylammonium hydroxide (TBAH), under organic/aqueous bilayer conditions. The fullerenol exhibited high water solubility, up to 64.9 mg/mL, under neutral (pH = 7) conditions. Dynamic light-scattering (DLS) analysis showed a narrow particle size distribution, of 1–2 nm, indicating that the fullerenol had high dispersion properties in water. The results of particle size analyses, which both focused on a single nanoregion and were conducted using a novel induced grating (IG) method and a scanning probe microscope (SPM), were consistent with the DLS results. A plausible reaction mechanism, which includes fullerene oxide intermediates detected by liquid chromatography-mass spectrometry (LC-MS), has been proposed.

We report a BF3-mediated novel dehydrative cycloaddition reaction of benzoquinones with stilbene oxides to afford 2,3-diaryl-5-hydroxybenzofurans and 2,3-diaryl-5-hydroxydihydrobenzofurans in good combined yields. No change in the products or the yield is observed when using diphenylacetaldehyde and cis-stilbene oxide instead of trans-stilbene oxides. When stilbene oxide is reacted with hydroquinone instead of the corresponding benzoquinone under the same conditions, dihydrobenzofuran is isolated in high yield. On the basis of these results, we propose the following possible reaction mechanism: stilbene oxide is converted to a phenonium ion (the key intermediate), which undergoes nucleophilic attack by benzoquinone or the simultaneously generated hydroquinone and subsequent dehydrative intramolecular cyclization to afford benzofuran or dihydrobenzofuran, respectively.

We found a facile one‐step synthetic method for water‐soluble fullerenols bearing 8–16 nitrogen‐containing substituents as well as more than 16 hydroxyl groups from commercially available C60 as a starting material. The water solubility of one of the products showed the same as the highest one reported (>200 mg/mL). Other fullerenols bearing hydrogen or diethylamino group on the same fullerene cage were also synthesized by the modified method using hydrogen peroxide as a simple hydroxylation reagent.

The AlCl3-catalyzed acetylation of 1,2-hydrophenylated [60]fullerenes, HC60-Ar, proceeded via a sequential manner involving the acetylation at the hydrogenated fullerene carbon, the following intramolecular cyclization with the adjacent aryl group, the facile loss of water, and the second acetylation of the generated indenylidene double bond. However, the similar reaction of the hydrobiphenylated analogue brought about the normal acetylation at the terminal aromatic ring prior to the same sequential reactions as did hydrophenylated fullerenes.

Using a novel hydrogen peroxide heating method, we synthesized milky white, water-soluble polyhydroxylated fullerenes (fullerenols) with 36-40 hydroxyl groups (estimated average) along with 8-9 secondary bound water molecules. The fullerenols exhibited high water solubility up to 58.9 mg/mL in a neutral (pH = 7) condition. Dynamic light scattering analysis showed a high dispersion property, to give a narrow particle size distribution within 0.7-2.0 nm.

We investigated the antioxidant activity of supramolecular water-soluble fullerenes, polyvinylpyrrolidone (PVP)-entrapped C(60), and gamma-cyclodextrin (CD)-bi-capped C(60), based on comparable beta-carotene bleaching assay. Antioxidant activity against reactive oxygen species (ROS) generated by three different methods, (i) autoxidation of linoleic acid, (ii) hydrogen peroxide promoter, and (iii) photoirradiation, was evaluated as percent of inhibition relative to a control experiment in view of the bleaching rate constant (k(obs)) as well as the persistent absorbency of beta-carotene. Water-soluble fullerenes exhibit significant inhibitory effects on the oxidative discoloration of beta-carotene in any system.

[reaction: see text] Effects of metal cation recognition on photosensitized E-Z isomerization of 1,2-dichloroethylene have been investigated with two types of m,p- and o,o'-podand (oligo-oxyethylene unit) benzophenones 2 and 3. With increasing cation size, the %Z ratio at the photostationary state was changed from 67 to 91% for 2 but remained almost unchanged (86-88%) for 3. These results were interpreted in terms of the variation of excited triplet energy, E(T), associated with the cation complexation of these photosensitizers 2 and 3.

An irradiation of diphenylbicyclo[4.2.0]oct-3-ene-2,5-diones bearing variously substituted Me groups resulted in the reversible intramolecular [2+2] cycloaddition between the excited enedione C C double bond and the facing endo -phenyl ring to exclusively give pentacyclotetradeca-10,12-diene-2,7-diones. The equilibrated product ratios were much dependent on the substitution pattern of the Me-groups as well as the irradiated wavelength. The regiochemistry of these photoadditions was elucidated on the basis of the restricted conformation of the starting enediones.

1,2-Oxaphosphetanes bearing three phenyl groups directly bound to the phosphorus atom were successfully isolated for the first time as stable crystals in the typical Wittig reaction of cyclopropylidenetriphenylphosphorane with activated carbonyl compounds. X-ray analysis of the oxaphosphetane showed that the phosphorus atom is at the center of a slightly distorted trigonal bipyramidal structure. Thermal decomposition of these oxaphosphetanes was carried out to give the starting carbonyl compounds and Wittig reaction products, olefins.

[reactions: see text] We investigated the site selectivity switch in BF3-catalyzed dual skeletal rearrangements of cyclobutene-fused diarylhomobenzoquinones by changing the stoichiometric amount of acid concentration. From the lower to the higher equivalency of BF3 x Et2O, the branching product ratios (path A/path B) obeyed nonlinear sigmoid curves against the equivalency of BF3 x Et2O. The observed selectivity profiles were simulated to elucidate factors that govern thermodynamic aspects (binding affinity K of each carbonyl function with acid) and kinetic aspects (rate constants k for the cyclobutene-ring cleavage).

Lewis acid catalyzed rearrangements of highly strained [2 + 2] photoadducts 1a-d of diphenylhomobenzoquinone with various acetylenes were investigated under the influence of AlCl(3), SnCl(4), BF(3), and TiCl(4). With the relief of steric strain, these tricyclo[5.2.0.0(3,5)]non-8-ene-2,6-diones underwent the three steps of consecutive skeletal transformations. The first step was the two-way cyclobutene ring-cleavage reaction with a Wagner-Meerwein vinyl migration to either Lewis acid activated carbonyl function. This process virtually occurred under the anchimeric assistance of the endo-phenyl ring to give, after proton transfer, the phenylene-bridged tetracyclic keto alcohols 2 and 3, respectively. The next step was the acid-induced cyclopropane ring cleavage of only 3 to lead to bicyclic diones 4 via a following stereoselective proton transfer. The last one involved a Michael-type intramolecular cyclization of 4 accompanied by a proton transfer to afford thermodynamically less stable tricyclic diones 5alpha which epimerized to 5beta only by TiCl(4). The factors that control the selectivity and the reactivity of these tandem reactions were addressed on the basis of the X-ray crystal analyses as well as the PM3 calculations. It was found the present Lewis acid-catalyzed rearrangements were very dependent on the substituents of 1a-d and the nature of the Lewis acids.

Fast ring opening of mesoionic 1,3-dioxolylium-4-olate 5 , generated by Rh 2 (OAc) 4 -catalyzed decomposition of a phenyldiazoacetic anhydride 6 , to an acyloxyketene 10 was demonstrated by trapping the ketene 10 . Rh 2 (OAc) 4 -catalyzed decomposition of p -nitrophenyldiazoacetic p -chlorobenzoic anhydride 6a in the presence of ketenophiles such as dihydrofuran, carbodiimides, and imines did not give 1,3-dipolar cycloadducts with the 1,3-dioxolylium-4-olates 5a , but their [2+2]-cycloadducts with the acyloxyketene 10a . PM3 calculation of heats of formation of a 1,3-dioxolylium-4-olate 5 and an acyloxyketene 10 indicates that the acyloxyketene 10 is 9 kcal/mol more stable than the 1,3-dioxolylium-4-olates 5 .

Reactions of tricarbonyl compounds with vinyl diazo compounds 2 were carried out. Reaction of 1,2,3-indanetrione with 2a , b , c gave the spiroindan-1,3-dione-2,2′-benzodihydrooxepin 7a , b , c , but not normal products oxirane and dihydrofuran derivatives expected from intermediate vinyl carbonyl ylides 4 . Formation of 7 requires isomerization of vinyl carbonyl ylides 4 bearing a ( Z )-cyanostyryl group to unstable ( E )-form 5 and subsequent cyclization to oxepin 6 followed by a 1,5-hydrogen shift. However, reaction of 2 with six-membered cyclic tricarbonyl compounds 1,2,3-trioxo-2,3-dihydrophenalene 11 and dimethylalloxane 13 gave the dioxole 12 and the dihydrofuran 14 , respectively, typical products expected from vinyl carbonyl ylides.

Diels-Alder reactions of acyclic oligoether-substituted quinones 1b, 1c, 2b, and 2c with cyclopentadiene were accelerated by the addition of alkali and alkaline earth metal perchlorates, and scandium trifluoromethane sulfonate (k(c)/k(f) = 1.2-23 for univalent cations, 11-1160 for divalent cations, and 1700-192 000 for Sc(3+), where k(c) and k(f) are the rate constants for the metal complexed and uncomplexed quinones, respectively). The shorter-armed 1a, 2a, and 3, however, exhibited no such acceleration effects. The rate accelerations can be rationalized by the FMO consequence in which the bound guest cation withdraws electron density from the quinone dienophile and lowers the LUMO energy suitable for the orbital interaction with the HOMO of cyclopentadiene. Despite the poor cation selectivity, these acyclic oligoether quinones showed larger rate accelerations than the relevant quinocrown ethers 4 (k(c)/k(f) = 1.3-3.0 for univalent cations, 5.0-160 for divalent cations, and 100-2020 for Sc(3+)). The effective electron withdrawal, which leads to the enhanced rate acceleration, can be caused by the direct interaction between the metal cation accommodated in the pseudo-cyclic oligoether linkage and the quinone carbonyl oxygen, as indicated by (1)H NMR spectroscopy. In addition, the larger rate enhancement is rather achieved in the complex with low binding constant K, because the strong encapsulation of metal cation by the oligoether chain diminishes the crucial interaction to the quinone carbonyl oxygen. As a whole, the smaller and higher valent cations tend to bring about notable rate acceleration due to the more enhanced ion-dipole interaction with the quinone carbonyl oxygen. Spectroscopic titration (absorption and (1)H NMR) and kinetic experiments indicated that only the longest di-armed 2c constructs 1:1, and then 1:2, host/guest complexes with Ca(2+), Sr(2+), and Ba(2+). These 1:2 complexes exhibited the most effective acceleration for the respective metal cations.

When ‘thiocarbonyl ylide' 1A (=(2,2,4,4-tetramethyl-3-oxocyclobutylidenesulfonio)methanide) is generated from the dihydrothiadiazole 5A by N2 extrusion at 40° in the presence of 2,3-bis(trifluoromethyl)fumaronitrile ((E)-10), a cyclic seven-membered ketene imine 11 and trans-thiolane 12 are formed (81 : 19). The reaction of 1A with (Z)-10 furnishes 11, 12, and cis-thiolane 25 in the ratio of 82 : 12 : 6. The strained ketene imine 11 is crystalline and storable as a consequence of the stabilizing ‘perfluoroalkyl effect'. The ketene imine group is stereogenic; 11 has a transoid structure with respect to the CF3 groups, and there is no evidence for the cisoid diastereoisomer. Ketene imine 11 adds H2O, MeOH, and PhNH2. In solution at 60°, 11 undergoes an irreversible ring contraction, furnishing the thiolanes 12/25 98 : 2. The rate constant of this first-order rearrangement increases 850-fold, as the solvent polarity rises from cyclohexane to CD3CN, in accordance with a zwitterionic intermediate. It is the same intermediate that is initially formed from 1A and 10, and its intramolecular N- and C-alkylation give rise to 11 and 12+25, respectively. In contrast to 1A, thiocarbonyl ylide 27, which harbors the sterically less-demanding adamantylidene group, reacts with (E)-10 to give trans-thiolane 29, but no ketene imine. The precursor 26 catalyzes the (Z)/(E) isomerization of 10 ((E)/(Z) ca. 95 : 5 at equilibrium), thus obviating conclusions on steric course and mechanism of this cycloaddition.

Irradiation of a homobenzoquinone derivative with variously substituted alkenes and alkynes gave the [2 + 2] photocycloadducts, tricyclic diones, almost quantitatively as a mixture of regio- and stereoisomers. The preferred regioisomer for all reactions is attributed to the more stable 1,4-biradical intermediate (major addition mode), and the minor isomer is attributed to the less stable biradical (minor addition mode). A radical trapping experiment using benzeneselenol proved the generation of these two regioisomeric biradicals, reflecting the regioselectivity in selenol-free photoreaction. Both biradicals tended to preferentially yield the endo-isomer for the alkenes with smaller substituents such as ethoxy, cyano, and acetoxy groups, but the exo-isomer for the alkenes with larger substituents such as phenyl, carbazolyl, and tert-butyl groups. The logarithmic exo/endo ratios were well correlated with a combination of Taft's steric factor E(s) and the energy gain (DeltaE') associated with the orbital interactions between the spin centers of 1,4-biradicals. These results were interpreted in terms of Griesbeck's SOC mechanism as well as the possible bond rotation around the armed radical chain. Therefore, it is concluded that a balance of repulsive steric hindrance and the attractive FMO interaction determines the stereochemical course of the [2 + 2] photoaddition of homobenzoquinone derivative with variously substituted alkenes.

We studied the kinetics of the Diels-Alder reaction of Li(+)-encapsulated [60]fullerene with 1,3-cyclohexadiene and characterized the obtained product, [Li(+)@C60(C6H8)](PF6(-)). Compared with empty C60, Li(+)@C60 reacted 2400-fold faster at 303 K, a rate enhancement that corresponds to lowering the activation energy by 24.2 kJ mol(-1). The enhanced Diels-Alder reaction rate was well explained by DFT calculation at the M06-2X/6-31G(d) level of theory considering the reactant complex with dispersion corrections. The calculated activation energies for empty C60 and Li(+)@C60 (65.2 and 43.6 kJ mol(-1), respectively) agreed fairly well with the experimentally obtained values (67.4 and 44.0 kJ mol(-1), respectively). According to the calculation, the lowering of the transition state energy by Li(+) encapsulation was associated with stabilization of the reactant complex (by 14.1 kJ mol(-1)) and the [4 + 2] product (by 5.9 kJ mol(-1)) through favorable frontier molecular orbital interactions. The encapsulated Li(+) ion catalyzed the Diels-Alder reaction by lowering the LUMO of Li(+)@C60. This is the first detailed report on the kinetics of a Diels-Alder reaction catalyzed by an encapsulated Lewis acid catalyst rather than one coordinated to a heteroatom in the dienophile.

Antioxidant activity of hydroxylated fullerenes, so-called fullerenols, against lipid peroxyl radical was evaluated byβ-carotene bleaching assay. All samples showed moderate to high antioxidant activity (%AOA), especially for C60(OH)12(70.1) and C60(OH)44(66.0) as compared with 8, 24, 26, and 36 hydroxylated ones (31.7–62.8). The detection of the possible products was conducted in the model reaction of both fullerenols and C60with methyl linoleate by MALDI-TOF-MS. These results suggested that the two possible mechanisms, such as C-addition to double bonds and H-abstraction from –OH groups, are involved in the present radical scavenging reaction.

The tricyclic enedione, which was synthesized in the [2+2] photocycloaddition of homoquinone with alkyne, underwent a novel Lewis acid-mediated skeletal rearrangement to provide bi-, tri- and tetracyclic cage compounds, depending on the identity of the Lewis acid used. The prolonged reaction and the independent treatment of the intermediary products by other Lewis acids revealed that the reaction proceeds through successive, multi-step transformations involving a cyclobutene ring-cleavage, an intramolecular Friedel–Crafts addition, and a cyclopropane ring-opening as well as an intramolecular cyclization. The product distributions were governed by the identity of the Lewis acid and the coordinated carbonyl site.

Irradiation of various meta- and para-substituted homobenzoquinones with ethyl vinyl ether gave the [2 + 2] photoadducts, tricyclic diones, regio- and endo-selectively and in good yields. The tricyclic skeleton has an anti-form built by the addition of ethyl vinyl ether from the less hindered side of homoquinones. All of the CH3, Cl, Br, and CH3O substituents at the reacting CC double bond afforded head-to-head (HH) addition predominantly. In the case of CH3, Cl, and Br, the ethoxy group was oriented in the endo-position, while the CH3O substituent led to a 1/5 mixture with the exo-isomer. It was also found that the Br-substituted [2 + 2] adducts undergo a facile skeletal rearrangement, being converted into dihydro-o-benzoquinone monomethide derivatives for para-substitution and dihydrobenzofuran derivatives for meta-substitution, probably under the influence of the in situ generated HBr. Intramolecular [2 + 2] photocycloaddition of an alkenylhomobenzoquinone afforded a tetracyclic dione.

The kinetics of thermal cyclopropane ring-opening of a series of m- and p-substituted endo/exo diphenylbromohomonaphthoquinones 1a–i and the unsubstituted diphenylchlorohomonaphthoquinone 1j have been investigated and compared with biphenyl-2,2′-diylhalogenohomonaphthoquinones 2a,b. The first-order rate constants k/s−1 for 1a–i at 100 °C in toluene increased with the electron-donating ability of the substituents. The kinetic substituent effects were much more pronounced for the exo family than for the endo one and revealed the crucial role of the resonance contribution of diaryl groups; log (k/ko)exo = −1.99σ+ + 0.086 and log (k/ko)endo = −0.784σ+ + 0.002, respectively. The compounds 2a,b thermolyzed very quickly as compared with the corresponding diphenylhalogenohomonaphthoquinones 1e,j. The kinetic solvent effects on the thermolysis of representative compound 1e were so minute that the rates tended to slightly increase with the solvent polarity but decrease with the solvent basicity. These kinetic results were interpreted in terms of a concerted disrotatory ring opening of the incorporated cyclopropane ring.

The alkali metal complexation of 15- to 18-membered ring quinocrown ethers Q15–18, 18- and 24-membered diquinocrown ethers DQ18,24, and 18-membered quinobenzocrown ether QB18 is compared with that of the corresponding benzocrown ethers B15–18 and dibenzo crown ethers DB18,24 in electrospray ionization mass spectrometry (ESI-MS). The quinocrown ethers exhibit lower cation affinity than the benzocrown ethers, although the two crown series essentially show the same ion selectivity except 18-membered DQ18 which preferentially binds Na+. The reduced binding ability of the quinocrowns is interpreted in terms of the deformation of the crown rings by the steric repulsion with the quinone carbonyls as well as the electron withdrawing ability of the fused quinone.

1,3-Dipolar cycloaddition of 5-diazo-10,11-dihydro-5H-dibenzo[a,d]cycloheptene with 2,5-dimethyl-1,4-benzoquinone gave the less stable conformer of 10′,11′-dihydro-1,4-dimethylspiro[bicyclo[4.2.0]hept-3-ene-7,5′-(5′H-dibenzo[a,d]cycloheptene)]-2,5-dione (α-conformer) via a conformationally retained nitrogen extrusion from the sterically congested indazole adduct. X-Ray structure analyses revealed that the cycloheptene ring moieties adopt considerably strained twist-boat conformations in which the dihedral angles (θ) of the –CH2CH2– bridge are 77.1 and 27.3°, respectively. At 100 °C the α-conformer underwent a one-way conformational inversion to the more stable twist-boat conformer (β-conformer) with an almost gauche angle of θ = 55.5°. A kinetic study of the thermal inversion exhibited a small dependency on the quinone substituents as well as negligible solvent effects, providing the transition energy of 127 kJ mol–1. Semiempirical (PM3) calculations were performed to determine the optimized geometries of the α- and β-conformers as well as the inversion transition state structure, which were compared with the X-ray data.

Reactions of vinylcarbenoids with cyclic disulfides were carried out. Rh 2 (OAc) 4 -catalyzed reaction of vinyldiazo compounds 1a-c with biphenylene disulfide 6 gave 1,3-insertion adducts 7a-c as the sole products in very good yields, while the reaction with dithiaphenanthrene 9 afforded only 1,1-insertion adducts 10a-c .

Diphenyl-substituted 11- to 20-membered ring crown ether acetals 1a–d exhibit selective cation complexation with alkali metal ions and NH4+ in electrospray ionization mass spectrometry (ESI-MS). In addition, cation-bound crown ether dimers (sandwiches) and trimers have also been observed, especially for the smaller crown ethers. However, their binding ability is completely lost upon acetal hydrolysis. It has been found that these crown ether acetals tend to preferentially bind smaller ions as compared with the corresponding simple crown ethers possessing the same number of ring oxygen atoms. These results are discussed on the basis of ring-contracted deformation, hydrophobic effects of the diphenyl group and the reduced solvation energies of the complexes.

The crystal structures of the two thermally equilibrated conformational isomers of the epoxide 1′,5′-dimethyl­spiro[10,11-dihydro-5H-dibenzo[a,d]cyclo­heptene-5,8′-4′-oxatricyclo[5.1.0.03,5]octane]-2′,6′-dione, C23H20O3, have been determined by X-ray diffraction. In the tricyclic dione skeleton, the oxirane and cyclo­propane rings adopt an anti structure with respect to the conjunct quinone frame. The spiro-linked 10,11-dihydro-5H-dibenzo[a,d]cyclo­heptene ring of the major isomer has a fairly twisted boat form, folding opposite to the adjoining cyclo­propane methyl substituent, whereas the seven-membered ring of the minor isomer has an almost ideal twist–boat form, inversely folding to the side of the relevant methyl group. The conformational structures of these isomers have been compared with those of the corresponding isomers of the unepoxidized homobenzoquinone.

The ionic conductivity of [Li(+)@C60](PF6(-)) was measured in o-dichlorobenzene, and found to be higher than that of TBA(+)PF6(-). Electrochemical reduction of [Li(+)@C60](PF6(-)) without any supporting electrolyte gave the monovalent radical anion Li(+)@C60˙(-), as confirmed by the characteristic ESR signal and NIR absorption band.