The reaction of 3,5-dichloro-2,4,6-trimethylbenzonitrile oxide with chiral fluoro-substituted allyl sulfoxides

The title reaction allowed the synthesis, with total regio- and moderate stereo-selectivity, of chiral fluorosubstituted 4,5-dihydroisoxazoles.     

Unprecedented palladium-catalyzed cross-coupling reaction of alpha-bromo sulfoxides with boronic acids

[reaction: see text] A new Suzuki-type palladium-catalyzed reaction of boronic acids with alpha-bromo sulfoxides has been developed using a protocol similar to the well-documented reaction of boronic acids with aryl halides. Both cross-coupling and homocoupling processes were observed. The best yields in cross-coupling products were obtained when the presence of oxygen was carefully excluded using degassed solvents. The oxidative addition palladium complex intermediate could be isolated and characterized by X-ray single-crystal diffraction.     

Cross-metathesis reaction of vinyl sulfones and sulfoxides

Cross-metathesis reactions of α,β-unsaturated sulfones and sulfoxides in the presence of molybdenum and ruthenium pre-catalysts were tested. A selective metahesis reaction was achieved between functionalized terminal olefins and vinyl sulfones by using the ‘second generation’ ruthenium catalysts 1c-h while the highly active Schrock catalyst 1b was found to be functional group incompatible with vinyl sulfones. The cross-metathesis products were isolated in good yields with an excellent (E)-selectivity. Both the molybdenum and ruthenium-based complexes were, however, incompatible with α,β- and β,γ-unsaturated sulfoxides.     

Palladium-catalyzed reaction of boronic acids with chiral and racemic alpha-bromo sulfoxides

Palladium-catalyzed cross-coupling reactions of racemic alpha-bromo sulfoxides with boronic acids are carried out in either aqueous or nonaqueous medium with formation of a new C sp(3)-C sp(2) bond. The arylation of chiral alpha-bromo sulfoxides occurs without racemization. The cross-coupling reaction is general and gives high yields with arylboronic acids substituted with either donor or acceptor groups but gives poor results with heteroarylboronic acids. The best yields are obtained using degassed solvents and CsF instead of aqueous base. The use of aqueous base and the presence of oxygen favor the homocoupling side reaction.     

Synthesis of substituted pyrroles in the glaser reaction

The substituted pyrroles and dipyrroles along with diacetylenes and cumulenes have been synthesized in high yields using a new synthetic method under mild reaction conditions using the Glaser coupling reaction. Although diacetylenes are formed from 2‐propargyl‐1,3‐dicarbonyl compounds having electron‐donors substituents such as Ph or OEt, only polyfunctional substituted cumulenes are formed from those compounds under the modified conditions. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:66–73, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20184     

低价钨化合物反应的研究-结构组成及其与亚砜和N-氧化吡啶的还原反应

六氯化钨-正丁基锂(1)与六氯化钨-锌(2)能将亚砜还原为相应的硫醚,将N-氧化吡啶还原为吡啶,在合适的条件下,产率高于90%.分离了六氯化钨与正丁基锂在四氢呋喃中产生的低价钨化合物,运用物理分析方法(ESCA,IR,1H和13C NMR)测得其组成为WCl4(THF)n.     

Synthesis of 2,5-disubstituted pyrroles by the reaction of ketoximes with 1,2-dibromopropane

Conclusions The reaction of ketoximes with 1,2-dibromopropane in the KOH-DMSO system gave 2,5-disubstituted pyrroles in 21–56% yield.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2175–2177, September, 1988.     

Pt(II)-catalyzed hydroarylation reaction of alkynes with pyrroles and furans

A Pt(II) catalyst showed a drastic effect on hydroarylation of alkynes with pyrroles and furans compared with Pd(OAc)₂ catalyst. The hydroarylation reactions proceeded smoothly under mild conditions to give double-hydroarylation products in good yields. Mono-adducts were formed only when the second hydroarylation was inhibited by steric hindrance of substrates or low reactivity of the mono-adducts.     

Kinetics, products, and mechanism of the reaction of diphenylcarbonyl oxide with sulfoxides

The kinetics of the reactions of diphenylcarbonyl oxide with dimethyl, di-n-hexyl, diphenyl, dibenzyl, andn-hexylbenzyl sulfoxides in acetonitrile was studied by flash photolysis at 295 K. The oxidation of sulfoxide affords the corresponding sulfone as the main reaction product, and diphenyl sulfide also forms in the case of Ph₂SO. Solvent effect on the reaction kinetics and the composition of the reaction products was studied. The reaction mechanism is discussed, which includes two parallel pathways: the nucleophilic attack of carbonyl oxide at the sulfur atom of sulfoxide and the formation of the cyclic sulfurane intermediatevia the electrophilic 1,3-cycloaddition of Ph₂COO at the S=O bond. The sulfurane undergoes fragmentationvia parallel channels to form sulfone or sulfide. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1504–1509, September, 2000.     

N-phosphorylation of pyrroles: An intramolecular migration reaction

A new synthetic method is reported for the N-phosphorylation of pyrroles via intramolecular migration of a phosphonate diester group. The reaction proceeds under mild conditions and produces N-phosphorylated pyrrole derivatives in moderate to good yields.     

Facile synthesis of N-substituted pyrroles via microwave-induced bismuth nitrate-catalyzed reaction

Simple synthesis of N-substituted pyrroles using microwave-induced bismuth nitrate-catalyzed reaction has been accomplished with an excellent yield. A plausible mechanism has been advanced. This reaction also provides a simple method to prepare diverse varieties of N-substituted pyrrole derivatives with less nucleophilic polyaromatic amines.     

Synthesis of pyrroles: reaction of chromium N-alkylaminocarbene complexes with alpha,beta-unsaturated aldehydes

N-alkylaminocarbene complexes of chromium were found to react with alpha,beta-unsaturated aldehydes to give pyrroles in good yields.     

The conformation of alkyl sulfoxides

Parameters for sulfoxides used in force field MM1 were modified to be incorporated into force field MM2. The conformations of ten alkyl sulfoxides were then calculated using MM2 with these new parameters. The alkyl groups used were methyl, ethyl, isopropyl, and t-butyl. It was found that of the many possible conformations for these compounds, only one or two stable conformers exist, and that the number of these conformers agrees with the number of reported S? O stretching frequencies in almost every case. No apparent correlation between the vibration frequency and the molecular structure was found.     

Effects of Si substitution on the Ei reaction of alkyl sulfoxides

A computational study has been carried out on the effects of SiH3 substitution on the Ei reaction of alkyl sulfoxides. SiH3 substitution in the beta-position (relative to the sulfur atom) is found to lower the barrier to elimination about 5 kcal mol(-1), in line with qualitative experimental observations. However, SiH3 substitution at the alpha-position has a similar, if smaller, effect. It is argued that the barrier-lowering in the latter case is mainly correlated with changes in the overall deltaH of the elimination reaction. In contrast, electronic effects in the transition state overcome an unfavorable delta(deltaH) when SiH3 is in the beta-position. On the basis of estimated magnitudes of the various energy changes and the fractional change in bond orders in the transition state, it is argued that both hyperconjugative stabilization and inductive effects of Si substitution contribute. Finally, it is shown that the elimination reaction by SiH3 transfer from Cbeta to O has a surprisingly high enthalpic barrier, given its modest endothermicity, and it is suggested that this is due to a forced unfavorable geometry at the Si center in the transition state.     

First synthesis of beta-keto sulfoxides by a palladium-catalyzed carbonylative Suzuki reaction

[reaction: see text] An unprecedented palladium-catalyzed three-component cross-coupling reaction between alpha-bromo sulfoxide, carbon monoxide, and aromatic boronic acids provides a new and efficient approach to the synthesis of beta-ketosulfoxides. The reaction takes place under mild conditions with a wide range of variously substituted aryl and heteroaryl boronic acids. The carbonylative cross-coupling reaction is strongly favored over competing direct cross-coupling and homocoupling processes, except with boronic acids carrying strong electron-withdrawing substituents.     

Formation of bicyclic pyrroles from the catalytic coupling reaction of 2,5-disubstituted pyrroles with terminal alkynes, involving the activation of multiple C-H bonds

Substituted bicyclic pyrroles are produced directly from the coupling reaction of 2,5-disubstituted pyrroles with terminal alkynes, involving the activation of multiple C-H bonds and regioselective cyclisation.