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PBBTZ (6H-pyrrolo[3,2-b:4,5-b′]bis[1,4]benzothiazine) was a p-type semiconductor with high field-effect transistor (FET) performance that we have just reported. Two trifluoromethyl substituted PBBTZ derivatives 3a and 3b were synthesized from facile one-pot condensation. They were characterized by means of 1H NMR, IR, HRMS (EI-TOF) and elemental analysis, furthermore, the crystal structure of 3b was described and discussed. Their optical properties were studied by UV-Vis and fluorescence spectroscopy, electrochemical properties were investigated by cyclic voltammetry (CV), and thermal properties were evaluated by thermal gravimetric analysis (TGA). The energy gaps of 3a and 3b, taken directly from spectroscopic measurements, are as broad as 2.45 and 2.48 eV, leading to bluish green and green photoluminescence. The LUMO and HOMO energy levels are −5.73 and −3.28 eV for 3a, −5.67 and −3.19 eV for 3b, respectively. The low energy levels render them well air-stable, and to be promising n-type semiconductor candidates for use in organic electronics.

A series of novel oligomeric electron donors containing two to six TTF cores (5–11) were synthesized. The structures were assigned by NMR spectroscopy, infrared spectrometry and mass spectra. Their electrochemical properties were investigated by cyclic voltammetry (CV). All the compounds exhibited two pairs of nearly ideal redox waves. No distinct shift of the redox potentials was observed when TTF units increased.

The sequential homoaldol-lactonization-alkylation/acylation- reactions of ethyl pyruvate with a variety of halides were achieved by using DBU along with Et 3 N as the base. The protocol provides an expedient one-pot synthesis of O-protected isotetronic acid derivatives. The high-yielding synthesis of an unprotected isotetronic acid is also described.

Ireland–Claisen rearrangement, triggered by silyl enolization of allylic but-3-enoates 2 , has been developed using DBU as the base in the presence of an excess amount of TMSCl under reflux in acetonitrile for a couple of hours. The procedure allows the synthesis of a range of 2-ethylidene-γ,δ-unsaturated carboxylic acids 5 in moderate to high yields. It is further revealed that the rearrangement proceeds equally well with allylic ( E )-hexa-3,5-dienoates 10 derived from sorbic acid under similar conditions to provide 2-allyl substituted hexa-2,4-dienoic acids 13 .

A soluble polymer (MeO-PEG) supported biphenylbisphosphine (BIPHEP)-Ru/chiral diamine (1,2-diphenylethylenediamine) complex, in which the polymer is attached to the two phenyl rings of BIPHEP ligand, has been prepared, and shown to be highly active with good enantioselectivity for the catalyzed asymmetric hydrogenation of unfunctionalized aromatic ketones. The derived chiral ruthenium complex 5 proved to be stable in air allowing facile catalyst recycling. Especially for 4′- tert -butyl-acetophenone and 1-acetonaphthone, excellent ee values up to 96.5% and 95.9% have been obtained which are comparable to or even higher than the enantioselectivity achieved with 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl-Ru-DPEN catalyst under similar conditions.

The novel tricyclic heterocycles of 4,5-dihydro[1,2,4]triazolo[3,2- D][1,5]benzoxazepine derivatives were prepared by the cycloaddition of the corresponding bicyclic cationic 1,3-dipoles, which were easily generated from the azoacetates by reaction with AlCl 3 as a Lewis acid, to the triple bond of nitriles along with the consecutive ring expansion. The formation of products deviating from the normal reaction aptitudes was observed and the mechanistic aspects are discussed herein. Crystal diffraction analysis for two of the products unequivocally established the respective structures proposed.

A new strategy of heterogenizing homogeneous catalysts by encaging the quasi-homogeneous catalytic reaction into a zeolitic microcapsular reactor has been proposed. As an example toward achieving such goal, a highly stable, nanopalladium-entrapped zeolitic microcapsular reactor (Pd@S1) was successfully fabricated and evaluated for Heck coupling reaction. The Pd@S1 not only exhibits excellent reactivity at low Pd adoption ( Pd/PhI = 0.0025 ) during the reaction, but also can be reused for more than 10 runs with negligible loss of activity, in contrast to rapid decay of activity of conventional Pd/C catalysts. Such reusability can be explained by the encapsulation of the “quasi-homogeneous” reaction mechanism of Heck coupling within the micrometer-sized hollow cavities of Pd@S1, which successfully avoids the Pd leaching during the reaction. The strategy may be helpful in the design of reusable, highly efficient catalysts with advantages deriving from both homogeneous and heterogeneous catalysts.

A novel DABCO-catalyzed Ireland-Claisen [3,3]-rearrangement of allylic acrylates to give a-methylene-γ,δ -unsaturated carboxylic acids in the presence of an excess of TMSCl and DBU in refluxing acetonitrile was developed. The protocol provides an easy entry to a-methylene-γ,δ-unsaturated carboxylic acids from allylic alcohols in good yields.

Derivatives of two new heterocyclic systems, namely furo[3,2-c][1,2,4]triazolo[1,5-a]azepinium salts and furo[2,3-f][1,2,4]triazolo[1,5-a]azepinium picrates, were synthesized from bicyclic azo compounds and nitriles in the presence of antimony pentachloride or aluminum chloride. The crystal diffraction analysis of an example product is reported and confirms the structure.

In the presence of a Lewis acid catalyst, β,γ-unsaturated ketones bearing a vinylic TMS directing group react with aldehydes or imines to furnish zwitterionic intermediates, which undergo an oxy-2-oxonia(azonia)-Cope rearrangement.

Axially chiral biaryls exist widely in bioactive natural products and auxiliary ligands for homogeneous catalysis. The particular spatial arrangement of the two aromatic rings in the specific space determines their unique properties; therefore, how to effectively control their absolute configuration is the key issue. Within the last decade, the synthesis of axially chiral biaryls has been a research topic of great interest. Asymmetric biaryl coupling controlled by chiral palladium catalysts was first reported in 2000 and has greatly advanced the chemistry of transition-metal-catalyzed cross-coupling reactions. Most notably, some novel chiral auxiliary ligands such as ferrocene- or biaryl backbone-containing monophosphine, bisphosphines, bis-hydrazones, hydrazone–phosphines, diene and NHC ligands have been applied to this reaction. At the same time a broad range of aryl electrophiles such as phenols, aryl ethers, esters, carbonates, carbamates, sulfamates, phosphates, phosphoramides, phosphonium salts, and fluorides can now be coupled efficiently with boron reagents to afford functionalized axially chiral biaryl products with good to excellent yields and enantioselectivities in the presence of chiral palladium catalysts. In this review, we would like to summarize three main categories of chiral catalysts with discussion of their advantages and limitation.

The oxidative aromatization of the dehydroaromatization products to complex heterocyclic ring systems is exemplified.

While 2-unsubstituted pyrimidyl-hydrazones (I) give directly the [1,5-c] title compounds (II), 2-methyl- or 2-phenyl-substituted substrates (III) or (VI) give the [4,3-c] title compounds (IV) and (VII), which can be transformed into the [1,5-c] analogues via Dimroth rearrangement.

The mechanism of the samarium-catalyzed 1,5-regioselective azide-alkyne [3 + 2]-cycloaddition (SmAAC) reaction has been examined with quantum mechanical calculations at the B3LYP/6-31+G(d,p) level of theory with ECP51MWB on Sm. Four stepwise pathways were located, with two leading to the 5-endocyclic 1,5-disubstituted 1,2,3-triazole product PSmL2 (paths 1 and 2) and the other two to the exocyclic product ExoPSmCl2 (path 3) as well as 1,4-disubstituted 1,2,3-triazole RegPSmL2 (path 4), respectively. Among them, path 2 (R-COM1-TS12-COM2-TS23-COM3-TS3P-PSmL2) is the most favored one both in the gas phase and in toluene solution, which is in good agreement with the experimental data. Moreover, 1,1-insertion forming COM2 in path 2 is the rate-determining step. The computational results also infer that the participation of samarium catalyst changes the distribution of the electrostatic potential on the reactants' surface, which determines the polarization direction of the reactants and formation of different intermediates (COM1 and RegCOM1), and finally affects the regioselectivity. When solvent corrections for toluene are considered, the 1,1-insertion process is discouraged, while the intramolecular [1,3]-shift reaction is facilitated.

A general method to synthesize functionalized allyl α-amino acid derivatives through an irreversible oxy-2-azonia-Cope rearrangement is reported. In the presence of AlCl3, the reaction of imino ethyl glyoxalates with various β,γ-unsaturated ketones furnished the corresponding allyl α-amino acid derivatives. The key to the success of this method is the amide bond formation, which makes the rearrangement irreversible. This reaction system constitutes a new strategy for the synthesis of unusual allyl glycine derivatives, which are valuable synthetic intermediates. An efficient and operationally simple three-component version of this reaction was also performed.

The mechanism of the Lewis acid-catalyzed oxy-2-azonia-Cope rearrangement between β,γ-unsaturated ketones and imines leading to the formation of homoallylic amides and lactams has been theoretically studied using the B3LYP density functional theory methods enhanced with a polarized continuum solvation model. It was predicted that the SnCl 4 -catalyzed tandem dimerization/oxy-2-azonia- Cope rearrangement mechanism is highly preferred over the uncatalyzed version as well as the plausible tandem dimerization/Prins rearrangement mechanism. A two-step pathway was found for the overall reaction, involving the initial nucleophilic dimerization followed by the (3,3)-sig- matropic rearrangement. The latter phase was considered to be the rate-limiting step. Particularly, the transition states account for the experimentally observed stereoselectivities and Z/E selectivities. The high stereoselectivity and Z/E selectivity for the chiral cyclic substrates can be attributed to the relative conformational stabilities of TSs. Moreover, distortion-interaction analysis has been performed in an attempt to quantify the various contributions to the reac- tion transition states, and it revealed that interaction energy E II and distortion energy ∆Ed associated with the forma- tion of the 2COM2 complex are the determining factors to

The preparation of a novel chiral 2,2'-bis(MeO-PEG-supported)-6,6'-bis(diphenylphosphanyl)biphenyl (MeO-PEG-Biphep) ligand is described. The derived ruthenium complex catalyzes the hydrogenation of β-ketoesters in up to 99% yield and 99% ee under atmospheric pressure. The accelerating effects exerted by the PEG linkage are dramatic when compared to the unsupported analogue, MeO-Biphep-RuBr 2 . Furthermore, the catalyst can be recovered easily and the recycled catalysts were shown to maintain their efficiency in two consecutive runs, albeit with declining activity. One of the products, (S)-ethyl-3-hydroxy-3-phenylpropanoate, is useful in the preparation of (5)-fluoxetine.

A series of 2-acyl-2H-1,2,3-diazaphospholes 3 underwent ready 1,3-dipolar cycloaddition reactions with 9-diazofluorenes as the 1,3-dipole, yielding the respective bicyclic phosphiranes 5 or trimers 7 depending on the reaction conditions employed. The reaction is believed to proceed via the formation of the [3+2]-cycloaddition adducts followed by elimination of nitrogen from the cyclic azo moiety. In the case of 3c, the phosphatetraazabicyclooctadiene compound 6 has been isolated with no loss of nitrogen. Likewise, the dipolar cycloaddition reaction of diphenyldiazomethane with the >CP- moiety as the 1,3-dipolarophile gave phosphadiazabicyclohexenes 8 in 32–68% yields.

Single crystals of four cation radical salts based on an ethylenedisulfanyl linked tetrathiafulvalene (bis(ethylenedithiotetrathiafulvalenylsulfanyl)ethane, 1), 1·[TCNQF4]2, 1·PF6(CH2Cl2)0.5, 1·AsF6(CH2Cl2)0.5 and 1·BF4, were prepared by chemical oxidation and electrocrystallization. The crystal structures of these salts are described, along with their electrical conducting behaviors. For comparison, the crystal structure of the neutral donor is also reported. In the crystal of the 1·[TCNQF4]2 salt the donor molecules adopt a Z-shaped conformation with the two TTF moieties located at the trans-position of the bridge, which resembles what is observed in its neutral crystals. The charge on each TTF moiety is +1, and there is no continuous π–π overlap in this crystal, leading to insulator behavior in this salt with σrt < 10−7 S cm−1. The two salts with PF6 and AsF6 as the counter anion are isostructural, and in these salts the donor molecules adopt a U-shaped conformation with the two TTF moieties located at the cis-position of the bridge. The donor molecules are packed into two-dimensional layers, which serve as the conducting path. The stacking pattern in the crystal of 1·BF4 is similar to that in 1·PF6(CH2Cl2)0.5 and 1·AsF6(CH2Cl2)0.5. The crystals of salts 1·PF6(CH2Cl2)0.5, 1·AsF6(CH2Cl2)0.5 and 1·BF4 display semi-conducting properties from room temperature down to 60 K.

A synthetic approach to the previously unknown thieno[2,3-f][1,2,4]triazolo[1,5-a]azepine derivatives was efficient-ly accomplished by cycloaddition of the bicyclic 1-aza-2-azoniaallene salts 6, derived from 6,7-dihydrobenzo[b]thiophen-4(5H)-one hydrazones 4, to the triple bond of nitriles, followed by ring enlargement. The X-ray crystal diffraction analysis of the picrate 10a provided affirmative proof for the structural assignment made.

The synthesis of the tetrakis{2-[1-(2,4,6-trichlorophenyl)-1H-1,2,4-triazol-5-yl]ethoxymethyl}methane derivatives 5a–c, 6 and 7, and the nitrotris{2-[1-(2,4,6-trichlorophenyl)-1H-1,2,4-triazol-5-yl]ethyl}methane derivatives 9a–c, 10 and the picrate 11 has been accomplished by reaction of the 1-aza-2-azoniaallene salts 3 with either the aliphatic tetranitrile 1 or trinitrile 8, in high yields; the X-ray crystal structure of 5b is also reported.

(1-Chloro-2-trifluoromethylcyclohexyl)azo compounds 3a-d, prepared by oxidation of the hydrazones 2a-d of 2-trifluo-romethylcyclohexanone (1) with a slightly excess amount of tertbutyl hypochlorite, react with antimony pentachloride and a nitrite to afford the respective 2,3-disubstituted-9-trifluoromethyl-6,7,8,9-tetrahydro-5H-[1,2,4]triazolo[1,5-a]azepinium hexachloroantimonates 6a-j. The reaction mechanism comprises of the initial cycloaddition of the in situ generated 1-aza-2-azoniaallene salts 4 to the triple bond of nitrile, giving the spiro-substituted 5a-j, followed by rearrangement and concomitant ring enlargement. From 3a-c where R 1 aryl, the salts 6a-h are isolated in high yields. However, if ethyl (1-chloro-2-trifluoromethyl)azocarboxylate (3d) is employed, the neutral N(3)-unsubstituted analogues 7a and 7b are obtained and after usual basic work-up, are converted to picrates 8a and 8b respectively. For one compound 6f. the X-ray diffraction analysis has been carried out in order to confirm the structural assignment. A practical modified procedure for preparation of the crucial starting ketone 1 is also described.

An expedient synthesis of neutral [1,2,4]triazolo[3,2-d][1,5]-benzoxazepines 6a–e and their chalcogen analogues 6f–i was accomplished via cycloaddition of the heterocumulene cations (3a,b), generated sequentially by action of chroman-4-one as well as thiochroman-4-one ethoxy carbonylhydrazones (1a,b) with t-BuOCl and SbCl5, to the triple bond of nitriles and concurring ring enlargement and hydrolytic removal of the N(1)-ethoxycarbonyl group. The oily final products were characterized as their picrates.

A sequential Diels—Alder reaction/rearrangement of 1,3-dienes with α,β-unsaturated aldehydes is developed to form bicyclo[2.2.1]heptanone derivatives.

New chiral N,S-ligands with oxazoline and thiophenyl sub-stituents at benzene ring and benzylic postition have been pre-pared and applied in palladium-catalyzed asymmetric allylic alkylation reaction to provide the product with high yield and entantioselectivity (82%-93%)ee.

The reaction of dichloroborane BHCl2 with 3,3,3-trifluoro-prop-1-ene (TFP), and propene have been studied using B3LYP method with 6–31G+ basis set. Based on the calculations, all transition structures have parallelogram-like H-B-C-C four-center geometry with small deformations. The introduction of fluorine atoms changes the proportions of hydroborational products and reverses the regioselectivity.

Ethyl (l,l,l-trifluoro-2-propylidene)carbazate is converted with tert-butyl hypochlorite to the 2-chloro-l,l,l-trifluoro-2-propyl azo compound 2, which reacts with antimony pentachloride to produce the trifluoromethylated 1-aza-2-azoniaallene salt 3 as a highly reactive intermediate. The cation 3 is employed as a CF3-containing synthon for the preparation of the 5-trifluoromethylated 1H-1,2,4-triazoliumpicrates 6a-e.

A kind of useful precursors for the construction of vicinal diaryl-substituted macrocycles, 4,5-diaryl-1,8-dihalo-3,6-dioxaoctanes, was readily produced by reductive coupling of aromatic carbonyl compounds with 2-haloethanols in the presence of tin powder and chlorotrimethylsilane in moderate to good yields by a one-pot procedure.

The detailed dissociation mechanism of diborane (B 2 H 6 ) in dimethyl sulfide (Me 2 S) media has been studied at the levels of B3LYP/6-311G**//B3LYP/6-31G* and B3PW91/6-311G**//B3PW91/6-31G*. All the calculations predict a two-step mechanism for the dissociation and only one H-bridge bond is broken in each. In comparison with the dissociation of B 2 H 6 in vacuum or in hydrocarbon media, the participation of Me 2 S significantly lowers the activation barriers in the process. The barriers are even more lowered when solvent effect is embraced.

A peroxide monomer, 4,4′-divinyl benzoyl peroxide (DVBPO), was synthesized. Bulk copolymerization of DVBPO with methyl methacrylate (MMA) was initiated by di(2-ethyl hexyl)peroxy carbonate (EHP). DSC curves and the appearance of crosslinking of the product showed that DVBPO can copolymerize with MMA. The grafting copolymerization of butyl acrylate (BA) onto the copolymer was performed. The grafting efficiency (GE), determined by Soxhlet extraction, was high.

The title compound 4, i.e. 9-chloro-4,5-dihydro-2-ethyl-1-(2,4,6-trichlorophenyl)-1H-1,2,4-triazolo[3,2-d]-[1,5]benzoxazepinium hexachloroantimonate, is a novel 6-7-5 tricyclic heterocycle. C18H14Cl4N3O·SbCJ6, M = 764.61, P21/c(#14), a = 13.457(4), b = 11.583(2), c = 18.992(3) A α = 90, β = 110.11(1)°, Z = 4, V = 2780(1) A3, Dc = 1.827 g/cc, μ (MoKα) = 19.69 cm−1, F(000) = 1488.00, T = 293 K, Rint = 0.055 for 3094 independent reflections with I>3.00σ(I). The five-membered heterocyclic ring is nearly planar, with the trichlorophenyl ring at N(2) almost perpendicular to it. However, the seven-membered ring is not planar, but adopts a twist-boat conformation.

Unprecedented [1,2,4]-Triazolo[3,2-d][1,5]benzoxazepine skeleton was easily achieved by cycloaddition of the allene-like cations 3, derived from 4-chromanone arylhydrazones, to the triple bond of nitriles and ensuing ring enlargement. The structural assignment of one product (5d) has been ultimately accomplished by X-ray diffraction analysis.

Two optically pure derivatives of α-cedrene — (1R,2R,5S,7R,8R)- 8-hydroxy-9-cedranone 2 and (lR,2R,5S,7R,8R,9S)-9-amino-8-hydroxycedrane 4 were prepared conveniently. An X-ray structural analysis of 2 was performed indicating that the hydroxycedranone exists as dimer due to one hydrogen bond in solid state.

Homologation of cedranediol boronic esters 1, RBO,C15H,4l with (dichloromethyl)lithium resulted in the formation of (αR)-α-chloro boronic esters 3, RCHCIBO2C15H24, consistently yielding (R)/(S)ratios over 25:1. The absolute configuration of cedranediol (R)-1-chloro-1-phenylmethylboronate 3dR was determined by X-ray diffraction. The distortion of the five-membered 1,3,2-dioxaborolane ring of 3dR from planarity was found. The reason why the cedranediol boronic esters are prone to hydrolysis has been discussed.

(-)-Cedranediol boronic esters 4, a series of asymmetric homologation reagents were prepared from a new chiral director (-)-cedranediol 3 and boronic acids. (-)-Cedranediol 3 was easily synthesized by the dihydroxylation of (-)-α-cedrene 2 with OsO4. A more convenient method for the preparation of boronic acids was developed as well.

In the presence of a Lewis acid, β,γ-unsaturated ketones and oximes or imines undergo nucleophilic addition to produce zwitterion intermediates, and subsequent oxy-2-azonia-Cope rearrangements give homoallylic amides. In the case of 2-vinylcycloalkanones, the process results in ring enlargement, providing a novel route to 9- to 16-membered lactams. The preparative significance of this protocol was evidenced by a short synthesis of macrocyclic alkaloid motuporamine G. The stereochemistry-defining step of this oxy-azonia-Cope rearrangement was further studied computationally. Despite a high-energy preequilibrium in the formation of zwitterionic intermediates, the [3,3]-sigmatropic step is the rate- and product-determining step. Chairlike transition states are generally preferred over boatlike ones.

[reaction: see text] Diaryl ethers have been prepared by direct coupling of phenols including those that bear a strong electron-attracting substituent to electron-deficient aryl halides through S(N)Ar-based addition reactions with assistance of microwave irradiation in high to excellent yields within 5-10 min. No catalysts were required under our conditions.

In the presence of a Lewis acid, β,γ-unsaturated ketones and oximes or imines undergo nucleophilic addition to produce zwitterion intermediates, and subsequent oxy-2-azonia-Cope rearrangements give homoallylic amides. In the case of 2-vinylcycloalkanones, the process results in ring enlargement, providing a novel route to 9- to 16-membered lactams. The preparative significance of this protocol was evidenced by a short synthesis of macrocyclic alkaloid motuporamine G. The stereochemistry-defining step of this oxy-azonia-Cope rearrangement was further studied computationally. Despite a high-energy preequilibrium in the formation of zwitterionic intermediates, the [3,3]-sigmatropic step is the rate- and product-determining step. Chairlike transition states are generally preferred over boatlike ones.

Uncertain knowledge management is a key issue in the expert system. By analysis of the reasons for knowledge’s uncertainty in complete universe and uncompleted universe, two methods based on set-theoretic granular computing are presented to deal with the uncertainty knowledge which is the rough observable method and rough inclusion method respectively. The rough set can be approximately expressed as a union of some basic sets on the given universe using the concepts of rough membership function and rough observable set. Experiments on the information system show that the original indefinite sets can be described with its approximate sets, which have the certain knowledge. So the uncertainty sets have the certainty at some degree, and from which one can get more deterministic information.

An unprecedented stereoselective allylation is observed in the Lewis acid-catalyzed reaction of simple aldehydes with β,γ-unsaturated carbonyl compounds.

The mechanisms of cycloaddition reactions between 1-aza-2-azoniaallene cations 1 and acetylenes 2 have been investigated using the global electrophilicity and nucleophilicity of the corresponding reactants as global reactivity indexes defined within the conceptual density functional theory. The reactivity and regioselectivity of these reactions were predicted by analysis of the energies, geometries, and electronic nature of the transition state structures. The theoretical results revealed that the reaction features a tandem process: an ionic 1,3-dipolar cycloaddition to produce the cycloadducts 3 H-pyrazolium salts 3 followed by a [1,2]-shift affording the thermodynamically more stable adducts 4 or 5. The mechanism of the cycloaddition reactions can be described as an asynchronous concerted pathway with reverse electron demand. The model reaction has also been investigated at the QCISD/6-31++G(d,p) and CCSD(T)/6-31++G(d,p)//B3LYP/6-31++G(d,p) levels as well as by the DFT. The polarizable continuum model, at the B3LYP/6-31++G(d,p) level of theory, was used to study solvent effects on all the studied reactions. In solvent dichloromethane, all the initial cycloadducts 3 were obtained via direct ionic process as the result of the solvent effect. The consecutive [1,2]-shift reaction, in which intermediates 3 are rearranged to the five-membered heterocycles 4/5, is proved to be a kinetically controlled reaction, and the regioselectivity can be modulated by varying the migrant. The LOL function and RDG function based on localized electron analysis were used to analysis the covalent bond and noncovalent interactions in order to unravel the mechanism of the title reactions.

With the further expansion of college enrollment, and the growing size of schools, the management of students becomes more complex and onerous. School development based on the student information management is becoming higher and higher, to facilitate the school management to ensure that student information is secure, accurate, and should rely on advanced information technology to solve various problems encountered in the management proposed for centralized management of university student information management system design ideas.

This study was performed to investigate the reactivity of azocarbenium salts derived from 5α-cholestan-3-one towards 1,3-dipolar cycloaddition reactions with inverse electron-demand to produce unprecedented steroidal heterocyclic derivatives, i.e. [1,2,4]-triazolo-annulated 3-aza-A-homocholestanes 8 and 11 and picrates 12. The synthetic steps were comprised of oxidizing hydrazones 3 with tert-butyl hypochlorite to germinal chloroazo compounds 4, generation of the 1-aza-2-azoniaallene cations 5 by action with equimolar antimony pentachloride and interception with nitrile and alkyne molecules by cycloaddition to the triple bond followed by ring enlargement. The structure of the compounds was principally established on the basis of the analytical and spectral data along with the previously published X-ray diffraction analysis on 8a.

Treatment of propargylic esters of type (I) and (IV) with gold(I) catalysts results in unexpected rearrangement to cyclohexadiene derivatives like (II).

An unexpected gold(I)-catalyzed homo-Rautenstrauch rearrangement of 1-cyclopropyl propargylic esters to cyclohexenones is disclosed. This rearrangement represents new evidence for the recently discussed gold-stabilized nonclassical carbocation character of intermediates in gold catalysis. A mechanistic study proved partial chirality transfer from optically active propargyl acetates.

Simple allenyl ethers have been shown to be efficiently activated by cationic gold(I) catalysts to form reactive dienophiles in intermolecular Diels-Alder reactions. A range of different dienes give the cycloaddition products in moderate to excellent yields and good selectivity.

A novel metathetic cycloreversion of 7-vinyl- and 7-aryl-bicyclo[3.2.0]heptenones is described giving rise to linear polyene ketones with high selectivity.