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Herein, we report a visible‐light‐induced [2+2+1] dearomative cascade cyclization of indole/furan alkynes with NaHSO3, providing an array of diverse highly strained sulfonyl polycycles. Compared to our previous work, this method does not require the use of additional sacrificial oxidants and have wider reaction scope. Preliminary mechanistic studies suggest that the indole moiety initiated the reaction, which proceeded via single‐electron oxidation pathway. An alkenyl radical formed by intramolecular addition capture SO2, and the resulting specie is cyclized to furnish the final product. Also, DFT calculations disclosed that the groups on the indole ring or at the side chain probably affect the single electron distribution at the reaction site of IM‐RC‐I, and the distribution may be a decisive factor of spirocyclization. [ABSTRACT FROM AUTHOR]

4‐Aryl‐1,3‐dihydroxy‐2‐naphthoates having the less accessible 1,2,3,4‐tetrasubstituted naphthalene scaffold and that show photoluminescence emission from solid state as well as in solutions, were selectively synthesized from brominated lactol silyl ethers through the 1,2‐aryl‐migrative ring rearrangement reaction. [ABSTRACT FROM AUTHOR]

We present a strategy to the core structure of the alkaloid palhinine A passing through a 2,5-difunctionalized cyclohexenone. This enone was prepared by a domino Michael/aldol condensation sequence. An allylation reaction on the cyclohexenone followed by oxy-Cope rearrangement introduced an allyl group at C3. After the generation of an aldehyde function on the terminus of the C5 substituent, an intramolecular aldol reaction led to a bicyclo[2.2.2]octanone. The five-membered ring of the core structure could be established by an intramolecular nitrile oxide-alkene [3+2]-cycloaddition. Prior to this key transformation, the keto function was converted to an alkene and the allyl group to an oxime. [ABSTRACT FROM AUTHOR]

An intramolecular benzyne–phenolate [4+2] cycloaddition is reported. Benzyne precursors, having vicinal halogen‐sulfonate functionalities, linked with a phenol(ate) by various tether groups undergo efficient intramolecular [4+2] cycloaddition by treatment with either Ph3MgLi or nBuLi for halogen–metal exchange to form various benzobarrelenes. [ABSTRACT FROM AUTHOR]

An intramolecular benzyne–phenolate [4+2] cycloaddition is reported. Benzyne precursors, having vicinal halogen‐sulfonate functionalities, linked with a phenol(ate) by various tether groups undergo efficient intramolecular [4+2] cycloaddition by treatment with either Ph3MgLi or nBuLi for halogen–metal exchange to form various benzobarrelenes. [ABSTRACT FROM AUTHOR]

Nitrogen‐containing polycyclic aromatic compounds (N‐PACs) are an important class of compounds in materials science. Reported here is a new aza‐annulative π‐extension (aza‐APEX) reaction that allows rapid access to a range of N‐PACs in 11–84 % yields from readily available unfunctionalized aromatics and imidoyl chlorides. In the presence of silver hexafluorophosphate, arenes and imidoyl chlorides couple in a regioselective fashion. The follow‐up oxidative treatment with p‐chloranil affords structurally diverse N‐PACs, which are very difficult to synthesize. DFT calculations reveal that the aza‐APEX reaction proceeds through the formal [4+2] cycloaddition of an arene and an in situ generated diarylnitrilium salt, with sequential aromatizations having relatively low activation energies. Transformation of N‐PACs into nitrogen‐doped nanographenes and their photophysical properties are also described. [ABSTRACT FROM AUTHOR]

This Minireview focuses on selected topics in the syntheses of bicyclo[1.1.1]pentane (BCP) analogues. A brief historical introduction was included. The content covers various synthetic routes of 1‐substituted and 1,3‐disubstituted BCPs. Selective examples of synthetically useful building blocks are summarized for each category for synthetic organic chemists' and medicinal chemists' reference. A compare‐and‐contrast analysis is also applied to evaluate these routes and to demonstrate the progress of strategic functional group transformations using modern organic methodologies. By systematically analyzing the synthetic strategies to access these strained molecules, we also hope that this Minireview will provide inspirations for future developments in this area. [ABSTRACT FROM AUTHOR]

This review covers the strategies for the synthesis of 9H‐pyrrolo[1,2‐a]indole and 9H‐pyrrolo[1,2‐a]indol‐9‐one derivatives. Both metal‐promoted or non‐metal catalyzed transformations will be developed, including some relevant applications. [ABSTRACT FROM AUTHOR]

Substitutional doping of perylene with two boron atoms at the 6b/12b positions and two oxygen or nitrogen atoms at the 1/7 positions has been achieved. The modular synthesis route developed for these bis‐BO‐ (3) and bis‐BN‐perylenes (5) starts from the readily accessible borinic acid derivative of the doubly brominated 9,10‐dihydro‐9,10‐diboraanthracene (DBA), 1,5‐Br2DBA(OH)2. A Stille‐type reaction first furnishes the alkynyl‐substituted species 1,5‐(RCC)2DBA(OH)2 (2), which undergo double ring closure to afford 3 via the gold‐catalyzed addition of the O−H bonds to the C≡C bonds. Treatment of 2 with MeN(SiMe3)2 leads to aminoborane intermediates 1,5‐(RCC)2DBA(N(H)Me)2, which can be ring‐closed to give 5 in a similar manner as in the case of 3. Different substituents R (such as Me, tBuPh) can be introduced at the 2/8 positions of the perylene core. The products obtained undergo reversible reduction and are efficient blue/turquoise emitters. [ABSTRACT FROM AUTHOR]

Julolidines constitute a class of N‐heterocycle compounds which have in common the 2,3,6,7‐tetrahydro‐1H,5H‐benzo[1,2]quinolizine ring. Due mainly to its fluorescence properties, such structures have shown potential application in a range of scientific and technological areas and have attracted attention of a great variety of research groups. For example, julolidines have been used for detection of ions and volatile compounds in environmental and biological samples, to the construction of dye‐sensitized solar cells, photoconductive materials and as fluorescent sensors for bioimaging. This review summarizes the strategies reported to the synthesis of the julolidine ring and the principal modifications for obtaining more complex julolidine derivatives with improved fluorescence properties of these compounds. In this context, aldol condensation, olefination, imine synthesis, and cross‐coupling reactions have been extensively explored and discussed. Examples of applications, which illustrate the great potential of such structures, will also be briefly presented. [ABSTRACT FROM AUTHOR]

A one‐pot, transition‐metal‐free, domino Michael/SNAr protocol of general applicability has been devised for the regioselective synthesis of polyfunctional naphthalenes by employing nitromethane and ortho‐haloaryl ynones. Utilization of nitromethane as a one carbon carbanion source that is incorporated into a variety of ynones, ends up as an aromatic nitro substituent. The application of this domino process towards a total synthesis of the polycyclic alkaloid macarpine demonstrate for the efficacy of this methodology. The conceptually simple approach to affect regioselective, multifunctional benzoannulation of ynones displays wide substrate scope and functional‐group tolerance and has been implemented with substituted nitromethanes, as well as with alicyclic o‐haloynones. A one‐pot, transition‐metal‐free, domino Michael/SNAr process was devised for the regioselective synthesis of polyfunctional naphthalenes by employing nitromethane and ortho‐haloaryl ynones. Nitromethane was utilized as a one‐carbon carbanion source that is incorporated into a variety of ynones, ending up as an aromatic nitro substituent. This reaction was used in the total synthesis of the polycyclic alkaloid macarpine. [ABSTRACT FROM AUTHOR]

An unexpected homologation/dyotropic rearrangement/interconversion/[3+2] cycloaddition cascade reaction of α‐diazoester‐terminated N‐propyl‐substituted isatin derivatives was achieved in the presence of a chiral N,N′‐dioxide/ScIII catalyst. This catalytic manifold allows rapid construction of several classes of dimeric polycyclic compounds with good yields and high levels of diastereo‐ and enantioselectivity (up to 99 % ee). Furthermore, macrocyclic dimers can be obtained by an intermolecular homologation process. Simplifying complexity: A highly chemo‐ and enantioselective homologation/dyotropic transformation/interconversion/[3+2] cycloaddition cascade reaction of α‐diazoester‐terminated isatin derivatives with a three‐carbon tether was achieved. Dimeric polycyclic compounds containing multiple quaternary carbon centers were synthesized in one pot in the presence of a chiral N,N′‐dioxide/ScIII catalyst. [ABSTRACT FROM AUTHOR]

The metal‐free, green and highly atom‐economic formal [3+2] tandem cyclization is ideal for sustainable reaction development. It can be employed to synthesize unique 11H‐pyrido[3′,2′:4,5]pyrrolo[3,2‐b]indolizines from 7‐azaindoles and pyridotriazoles through a TsOH‐induced efficient process. [ABSTRACT FROM AUTHOR]

An efficient synthetic route towards previously inaccessible 7‐bromo‐1,3‐diazapyrenes through an in‐melt peri‐cyclization of readily available 7‐(5‐bromo‐3,4‐dihydropyrimidin‐4‐yl)‐1H‐perimidines is described. [ABSTRACT FROM AUTHOR]

A methodology for the synthesis of indolo[1,2-b]isoquinoline derivatives by Lewis acid-catalyzed intramolecular Friedel–Crafts alkylation reaction has been developed. The reaction proceeds well with both secondary and primary 2-indolylmethanols. The method efficiently affords pharmaceutically important polycyclic fused indole derivatives in moderate to high yields with good functional group tolerance. In addition, the reaction proceeded in large scale indicating that this method could be scaled up for the synthesis of indolo[1,2-b] isoquinoline derivatives. [ABSTRACT FROM AUTHOR]

Abstract: A bio‐inspired, pyrrolidine‐mediated, dimerization of para‐quinols has been developed. It represents one of the most complex, yet general, dimerization reactions ever disclosed, selectively forming four new bonds, four new rings, and eight new contiguous stereogenic centres. The para‐quinol starting materials are easily handled, bench‐stable compounds, accessed in just one step from aromatic feedstocks. The reaction can be scaled up to give grams of polycyclic material, primed for further elaboration. [ABSTRACT FROM AUTHOR]

Abstract: The synthesis and optical properties of 1,8‐diphenyl‐9,10‐bis(arylethynyl)phenanthrenes, which are distorted phenanthrenes, are reported. The presence of the two phenyl groups at the 1,8‐positions of phenanthrene significantly distorts the molecular geometries, as was evidenced by X‐ray crystallography. The congested substitution pattern in the K region results in a distorted aromatic framework, which leads to a redshift in the emission spectrum. These observations are in stark contrast to 9,10‐bis(phenylethynyl)phenanthrene with no phenyl groups at the 1,8‐positions. A large Stokes shift suggested extensive structural relaxation between the phenyl and arylethynyl units in the excited state, which was supported by theoretical calculations. [ABSTRACT FROM AUTHOR]

An efficient one-pot synthesis of indenes from simple starting materials is presented. This process involves a dual C-C bond formation through an intermolecular Heck coupling reaction followed by acid-mediated intramolecular cyclodehydration. The strategy is amenable to various substituted aro- matics to give indenes. In addition, the regioselective synthesis of benzyl styrenes in a single column purification technique through in-situ reduction of Heck products (ketones) followed by acid mediated dehydration of crude reaction mixture is presented. [ABSTRACT FROM AUTHOR]

Aryl diacetic mono-acid mono-esters were designed and efficiently synthesized as mono-protected bifunctional building blocks for the Perkin condensation between arylacetic acids and arylglyoxylic acids. Although, so far, this Perkin strategy has only been used for the formation of linear trimers or macrocyclic tetramers, it can now be adapted to the formation of pentameric conjugated species to give access, after adequate intramolecular cyclizations, to longer and more complex carboxy- substituted polycyclic aromatic compounds. [ABSTRACT FROM AUTHOR]

Diels-Alder reaction of symmetrical/unsymmetrical benzo[ c]furans with acenaphthylene in xylenes at reflux temperatures followed by p-toluenesulfonic acid-mediated epoxide cleavage and dehydration furnished diaryl/heteroaryl-substituted benzo[ k]fluoranthenes. This strategy could be successfully applied to the synthesis of dimeric and trimeric benzo[ k]fluoranthenes. Functionalization of representative benzo[ k]fluoranthene derivatives was also performed. UV/Visible, emission and electrochemical properties of representative fluoranthene derivatives are also reported. [ABSTRACT FROM AUTHOR]

A new alkyne annulation strategy has been developed for the synthesis of polycyclic indole derivatives through a cascade of C-H annulation and Michael addition reactions. This is the first report on sequential alkyne annulation and aza-Michael addition reactions of indole-1-carboxamides with alkyne tethered substrates. [ABSTRACT FROM AUTHOR]

The synthesis of highly functionalized spirocarbocyclic oxindoles was accomplished for the first time, using a Hauser annulation strategy. A reaction between methylene-indolinones and arylsulfonylphthalides catalyzed by cesium carbonate gave access to a new class of biologically important spiro[indoline-3,2'-naphthalene] derivatives in very good yields. [ABSTRACT FROM AUTHOR]

The catalytic asymmetric synthesis of both α-substituted and α,α-disubstituted (quaternary) β-tetralones through direct α-functionalization of the corresponding β-tetralone precursor remains elusive. A designed Brønsted base-squaramide bifunctional catalyst promotes the conjugate addition of either unsubstituted or α-monosubstituted β-tetralones to nitroalkenes. Under these reaction conditions, not only enolization, and thus functionalization, occurs at the α-carbon atom of the β-tetralone exclusively, but adducts including all-carbon quaternary centers are also formed in highly diastereo- and enantioselective manner. [ABSTRACT FROM AUTHOR]

Selective inhibitors of histone deacetylase 6 (HDAC6) are an emerging class of pharmaceuticals due to the involvement of HDAC6 in different pathways related to neurodegenerative diseases, cancer, and immunology. Herein, the synthesis of ten new benzohydroxamic acids, constructed by employing the tetrahydrobenzothiazepine core as a privileged pharmacophoric unit, is described. This is the first report on the synthesis and isolation of octahydrodibenzothiazepines and octahydro-6 H-benzocycloheptathiazepines, which were then used to develop a new class of HDAC6 inhibitors. Evaluations of their HDAC-inhibiting activity resulted in the identification of cis- N-(4-hydroxycarbamoylbenzyl)-1,2,3,4,4 a,5,11,11 a-octahydrodibenzo[ b, e][1,4]thiazepine-10,10-dioxide and cis- N-(4-hydroxycarbamoylbenzyl)-7-trifluoromethyl-1,2,3,4,4 a,5,11,11 a-octahydrodibenzo[ b, e][1,4]thiazepine-10,10-dioxide as highly potent and selective HDAC6 inhibitors with activity in the low nanomolar range, which also show excellent selectivity on the enzymatic and cellular levels. Furthermore, four promising inhibitors were subjected to an Ames fluctuation assay, which revealed no mutagenic effects associated with these structures. [ABSTRACT FROM AUTHOR]

A 1,6-addition arylation reaction of para-quinone methides with α-isocyanoacetamides and electron-rich aromatic compounds under metal-free conditions has been developed. BF3 ·Et2O plays two roles in the reaction: catalyzing the cyclization of α-isocyanoacetamides to give oxazoles, and activating the para-quinone methides to achieve the 1,6-addition arylation process. The reaction shows good functional group tolerance, scalability, and regioselectivity. It is a consice protocol for the synthesis of diverse unsymmetrical triarylmethanes. Further transformation of the resulting triarylmethanes provides an efficient route to some functionalized molecules. [ABSTRACT FROM AUTHOR]

In this account, the synthesis and applications of pyrene-fused acenes, as well as pyrene-fused azaacenes, have been carefully reviewed. Moreover, the synthetic methods involving two key synthons (different lengths of dienes and ynes) have been included. Furthermore, the 'clean reaction' strategy has been introduced for the preparation of pyrene-fused acenes with a single terminal-pyrene unit from tetracene to octacene, as well as for the synthesis of pyrene-fused octatwistacenes and nonatwistacenes with double terminal-pyrene units. Similarly, the synthons and the synthetic methods for pyrene-fused azaacenes have also been summarized. The applications of pyrene-fused acenes and pyrene-fused azaacenes have been included. [ABSTRACT FROM AUTHOR]

The described mechanochemical methodology is an example of a proof-of-concept in which solution-based tedious, poor yielding, and difficult syntheses of pyrazaacenes are achieved under solvent-free ball-milling conditions; the method is easy, high yielding, time-efficient, and environmentally benign. The synthesized compounds also include pyrazaacenes (N-heteroacenes) that are octacene analogues containing pyrene building blocks. The compounds were sparingly soluble in common solvents, and column chromatographic purifications could be avoided after the solvent-free syntheses. The UV/Vis absorption spectra of the pyrazaacenes show intense absorption bands in the near-IR region. The single-crystal X-ray analyses of selected pyrazaacene derivatives showed pairwise π-π interactions and some C-H ···π interactions, which could account for some of the photophysical features of the compounds in the solid state. [ABSTRACT FROM AUTHOR]

Rational building strategies and appropriate synthons have been developed for the use of triptycene as a rigid presenting scaffold. Palladium-catalyzed cross-coupling reactions, such as Sonogashira and Suzuki couplings, were used to install a variety of different synthetic handles around the triptycene periphery in a high-yielding and controlled manner. These triptycene molecular handles were investigated for their potential in the construction of molecular arrays with defined spatial orientation e.g., for host-guest interactions or drug delivery systems. Such molecular synthons afforded expansion from the triptycene core by employing arm extension to increase the internal free volume characteristic of triptycene scaffolds for such applications. In addition, a range of mesogenic and glycosyl triptycene derivatives were achieved as a synthetic proof of concept for future work on potential drug delivery systems. [ABSTRACT FROM AUTHOR]

A systematic study on the regioselective cyclization of benzene- and naphthalene-based unsymmetrical diols with HBr (33%) in acetic acid at room temperature led to the formation of annulation products. By using this method, synthesis of a wide variety of anthracene, tetracene and naphtho[b]thiophene analogues was achieved in good to excellent yields. By employing HBr (33%) in acetic acid as a catalyst for regioselective cyclization of unsymmetrical diols was very facile and devoid of commonly encountered dihydroisobenzofuran formation. [ABSTRACT FROM AUTHOR]

A series of fluorescein dyes have been prepared from a common precursor through a very simple synthetic procedure, giving access to important precursors for fluorescent probes. The method has proven an efficient access to regioisomerically pure 5- and 6-carboxyfluoresceins on a large scale, in good yields, and with high regioisomeric purity. Furthermore, we have applied the method to the development of a new type of mixed fluorescein derivatives of 5-carboxyfluorescein. We have demonstrated the scope of the procedure by synthesizing a new type of double chromophore within the fluoro-Jade family. [ABSTRACT FROM AUTHOR]

Facile divergent total syntheses for azafluoranthene and dehydroaporphine alkaloids have been successfully developed. A common intermediate, a biarylsulfonamide-protected amino aldehyde, underwent either a cascade or a stepwise cyclization to furnish a tetracyclic skeleton related to the azafluoranthene alkaloids. Natural products, triclisine and telitoxine, were prepared to illustrate the use of this approach. Subsequent C-homologation of the aldehyde moiety on the same intermediate by means of a Wittig reaction allowed the synthesis of aporphine alkaloids, as exemplified by the preparation of dehydronornuciferine. This synthetic approach could be applicable to the syntheses of other azafluoranthene-related as well as aporphine-related alkaloids. [ABSTRACT FROM AUTHOR]

An efficient and convenient synthesis of useful linear cyclopentenone-fused polycyclic compounds has been achieved through a novel gold(I)-catalyzed transformation of diynes. The method demonstrates high product yields and tolerates of a wide variety of important functional groups. Gold-vinylidene formation, methoxy group migration, and Nazarov-type cyclization are proposed to be the key steps in the reaction pathway. The synthetic utility of this method is demonstrated by converting the product to eight-membered-ring-fused compound. [ABSTRACT FROM AUTHOR]

A conventional BF3·OEt2-mediated Bradsher-type cyclodehydration of 2-arylmethyl benzaldehydes in CH2Cl2 at room temperature gave polycyclic aromatic and heteroaromatic compounds. Alternatively, these compounds could be synthesized in better yields from 2-arylmethylbenzoic acids by triflic-acid-mediated cyclization followed by reductive dehydration. [ABSTRACT FROM AUTHOR]

The anodic treatment of 2,4-dimethylphenol offers a powerful and direct method for the construction of a dehydrotetramer with four contiguous stereocentres on a multigram scale. The installation of propellanes on this scaffold using enantiomerically pure carbonyl compounds leads to a mixture of diastereomers. This mixture is easily separable using standard chromatography and gives rise to optically pure cyclopenta[ b]benzofurans which are important scaffolds in a variety of natural products. The synthesis is easy to perform and allows a reliable access to chiral compounds with very high enantiomeric excess. It was possible to determine the absolute configuration of these compounds by comparison of experimentally recorded and calculated VCD spectra of all enantiomers. [ABSTRACT FROM AUTHOR]

New hexacyclo and octacyclo compounds have been synthesized by a short route whose key step consists of a single or double domino nucleophilic substitution of neopentyl-type iodides with potassium cyclopentadienide, followed by intramolecular Diels-Alder cycloaddition. [ABSTRACT FROM AUTHOR]

A π-conjugated twelve-porphyrin tube is synthesized in 32 % yield by a template-directed coupling reaction that joins together six porphyrin dimers, forming twelve new CC bonds. The nanotube has two bound templates, enclosing an internal volume of approximately 4.5 nm3. Its UV/Vis/NIR absorption and fluorescence spectra resemble those of a previously reported six-porphyrin ring, but are red-shifted by approximately 300 cm−1, reflecting increased conjugation. Ultrafast fluorescence spectroscopy demonstrates extensive excited-state delocalization. Transfer of electronic excitation from an initially formed state polarized in the direction of the nanotube axis ( z axis) to an excited state polarized in the xy plane occurs within 200 fs, resulting in a negative fluorescence anisotropy on excitation at 742 nm. [ABSTRACT FROM AUTHOR]

A novel nitrogen-doped corannulene derivative, 8-tert-butyl-6b2-azapentabenzo[bc,ef,hi,kl,no]corannulene, was synthesized by 1,3-dipolar cycloaddition of a polycyclic aromatic azomethine ylide with a diarylethyne and subsequent palladium-catalyzed intramolecular cyclization. This molecule represents the first example of a corannulene derivative bearing an internal heteroatom, and exhibits unique structural and physical properties caused by the introduction of the nitrogen atom and extended π-conjugation, as compared to the parent corannulene. [ABSTRACT FROM AUTHOR]

The diastereoselectivity of the Pictet-Spengler cyclization of bicyclic N-acyliminium ions that contain a 3-azabicyclo[ n.3.0]alkane core and an electron-rich π-nucleophilic moiety, such as an indol-2-yl, indol-3-yl, 1-methylpyrrol-2-yl, or 3,5-dimethoxyphenyl group, was examined. The N-acyliminium ions were generated by protonation of the corresponding enamides or hemiaminals, which were derived from imides. Control of the quaternary stereocenter created at the newly formed ring junction was achieved in a diastereodivergent manner by fine-tuning the reaction conditions, which determined whether the reaction proceeded under kinetic or thermodynamic control. Mechanistic studies indicated that a retro-Pictet-Spengler reaction pathway is involved in the equilibration process. [ABSTRACT FROM AUTHOR]

A ZnCl2-promoted one-pot synthesis of multisubstituted thiazolo[4,5- b]pyridines and thieno[2,3- b:4,5- b′]dipyridines from mercaptonitrile salts, α-bromo ketones and ketones has been developed. This approach involves a tandem SN2 alkylation/Thorpe-Ziegler cyclization/Friedländer reaction, which allows the creation of two hetero rings and four new bonds in a single operation. The reaction proceeds smoothly under solvent-free conditions to afford fused pyridines in moderate to good yields. [ABSTRACT FROM AUTHOR]

The synthesis of tribenzotriquinacenes (TBTQs) that bear three phenylethynyl groups at the peripheral positions of the bowl-shaped molecular scaffold has been achieved by use of different strategies. Although the C1- and C3-symmetrical triformyl, triethynyl and triiodo derivatives were inseparable by chromatography, the corresponding C1- and C3-symmetrical tris(phenylethynyl)tribenzotriquinacenes were obtained in pure form. Threefold cyclocondensation of these TBTQ-based tris-tolanes with tetracyclone gave C1- and C3-tris(pentaphenylphenyl)tribenzotriquinacenes in good yields. Attempts to generate a completely closed graphene-like periphery around the TBTQ core by Scholl cyclodehydrogenation of the C3-symmetrical isomer failed. [ABSTRACT FROM AUTHOR]

The tandem reduction/oxidation of fluorenyl compounds was performed with LiAlH4 under air to afford the corresponding 9-hydroxyfluorenyl derivatives in good yields. This methodology with LiAlH4 is unprecedented and most likely proceeds by an organoaluminium intermediate, and in the proposed mechanism. [ABSTRACT FROM AUTHOR]

Masked o-benzoquinones (MOBs), which were generated in situ from 2-methoxyphenols, underwent Diels-Alder reactions with 1-vinylcyclohexenes to produce the corresponding cycloaddition products, that is, decahydrophenanthrenes along with bicyclo[2.2.2]octenones. In the former case, the MOBs serve as the dienophile, and in the later case, the 1-vinylcyclohexenes act as the dienophile. The obtained bicyclo[2.2.2]octenones could be transformed into the corresponding decahydrophenanthrenes through a Cope rearrangement at 220 °C. Thus, these tandem reactions provide a short and efficient entry to the decahydrophenanthrene skeleton from easily available 2-methoxyphenols. [ABSTRACT FROM AUTHOR]

A highly efficient palladium-catalyzed cascade reaction of propargyl carboxylates bearing a furanyl group with organoborons was developed. This methodology offers rapid access to polycyclic Diels-Alder cycloadducts in good to high yields. The thus-formed oxygen-bridged products were further converted into anthracene derivatives in a chemoselective manner under mild conditions. [ABSTRACT FROM AUTHOR]

New bisprimary and bisquaternary diamantane-1,6- and -4,9-diammonium/diaminium salts were synthesized, and characterized by NMR spectroscopy and X-ray crystallography. The impetus for these syntheses were previously reported X-ray crystallographic investigations of adamantane mono- and bisquaternary ammonium ions [3,5-diMeAda-1-NH3 or Ada-1,3-di(NMe3)] complexed with cucurbit[ n]uril ( n = 7, 8). The crystal structures were analyzed to ascertain possible structural hypotheses for high binding affinity guests bound within various diameter pumpkin-shaped hosts. Although Diam-4,9-di(NMe3I) 5 could be readily prepared from the bisprimary precursor, corresponding Diam-1,6-di(NMe3I) 14 could not be obtained even under strong reaction conditions. Stereochemical analysis of this situation suggests very severe steric non-bonding cis-1,3-diaxial type H ···H interactions between the 'axial'-type NMe3 group and neighboring 'axial' proton neighbors. These same interactions are found in Ada-2,6-di(NMe3I) analogues, but they are alleviated in this smaller polycyclic skeleton through tilting the axial C(methylene)-NMe3 bond away from its axial neighbors. However, similar structural relief for Diam-1,6-di(NMe3I) is not possible, because the C(methine)-NMe3 bond therein is ligated to the diamondoid's rigid skeleton. [ABSTRACT FROM AUTHOR]

Cycloaddition uncovered: The title reaction produces novel polycyclic compounds with high efficiency and excellent diastereoselectivity under mild reaction conditions. A small‐molecule library, synthesized using this reaction, yielded a novel chemotype which inhibited glycolytic ATP production by blocking glucose uptake in CHO‐K1 cells. DMF=N,N‐dimethylformamide, Tf=trifluoromethanesulfonyl, TIPS=triisopropylsilyl. [ABSTRACT FROM AUTHOR]

Hooray Horeau! Highly enantioselective organocatalyzed Diels–Alder reaction cascades are disclosed for the first time. The reaction enables the efficient and rapid construction of enantiopure polycycles from simple achiral, acyclic polyenes. [ABSTRACT FROM AUTHOR]

Unsaturated bicyclic carboxylic acids undergo palladium-catalyzed coupling with bromoalkynes to produce γ-alkynyl lactones in moderate to good yields with excellent chemo- and regioselectivity. The reaction conditions were extremely mild, and functional groups such as methyl, methoxy, chloro, and bromo were tolerated under the optimized reaction conditions. Moreover, γ-chloroalkenyl lactones were facilely synthesized through chloropalladation/carboesterification of electron-deficient C≡C bonds by using molecular oxygen as the sole oxidant. [ABSTRACT FROM AUTHOR]

Pharmaceutically useful dihydronaphthopyran derivatives were obtained in good yield by the regio‐ and stereoselective annulation of ortho‐naphthoquinone methides with allyl silanes. The ortho‐naphthoquinone methides were generated in situ from 1‐siloxymethyl‐1,4‐epoxy‐1,4‐dihydronaphthalenes under FeCl3 catalysis (see scheme; allyl‐TMS=allyltrimethylsilane, TBS=tert‐butyldimethylsilyl, TMS=trimethylsilyl). [ABSTRACT FROM AUTHOR]