Zirconocene-Catalyzed Silylation of Alkenes with Chlorosilanes

Vinylsilanes and/or allylsilanes are formed upon silylation of terminal alkenes with R₃^′SiCl in the presence of a Grignard reagent and a catalytic amount of [Cp₂ZrCl₂] [Eq. (a)]. The reaction also proceeds under mild conditions when silylsulfides (X=SPh), silylselenides (X=SePh), and silyltellurides (X=TePh) are used in place of chlorosilanes (X=Cl). R″=alkyl, aryl, alkylsilyl; R′=Me, Et, nPr; R=CH₂R″, aryl, H.     

分子筛担载金催化剂催化烯烃环氧化制环氧化合物

烯烃的环氧化是工业上的重要反应之一，在众多的烯烃中，端烯尤其是直链端烯是相对较难氧化的一类。     

N‐Iodosuccinimide: A Highly Effective Regioselective Reagent for Iodoesterification of Alkenes

A rapid, convenient, and efficient method has been achieved for regioselective iodoesterification of alkenes with aliphatic and aromatic acids, and protected amino acids in the presence of N‐iodosuccinimide (NIS) in nearly quantitative yields. Optically enriched iodohydrins have been achieved by LiAlH₄ (LAH) reduction of diastereoisomeric iodo esters.     

烯烃在USY沸石表面上化学反应热的量热测定

1.前言 在多相催化研究工作中,测定反应物分子在固体催化剂表面上化学吸附时产生的反应热,或者说化学吸附热,对研究催化剂的性质和反应物的表面化学反应都很有帮助。但是目前尚无有效的方法测定它。本文用吸附量热法测定了烯烃在USY沸石表面的吸附热,并提出了一种化学吸附热的估算方法。     

Visible-light-promoted oxidative difunctionalization of alkenes with sulfonyl chlorides to access β-keto sulfones under aerobic conditions

A mild, practical and efficient strategy to prepare β-keto sulfones has been developed by visible light promoted reactions. This reaction involves Ir(ppy)₂(dtbbpy)PF₆ catalyzed direct funcationalization of alkenes with sulfonyl chlorides under mild conditions. Air was used as oxidant without any additives. The transformation affords the corresponding products in moderate to high yields.     

Implications of hyperconjugative effects on bond lengths of allylic systems. An NBO investigation

The influence of hyperconjugative interactions on bond lengths of some allylic compounds (H₂CCH–CH₂–M(CH₃)₃; M=C, Si, Ge) has been investigated through NBO calculations using ab initio and density functional methods. The optimized structural parameters, at the B3LYP/6-31+G(d,p) and HF/6-31+G(d,p) levels, showed a good agreement with the resonance theory. Partial geometry optimization with orbital interactions removed confirmed the observations and revealed that σ→σ* interactions, together with the more common σ→π* ones, play an important role in determining the variations in bond lengths on going from C to Ge.     

Rieke zinc as a reducing agent for common organic functional groups

The ability of Rieke zinc to reduce common organic functional groups has been studied. Nitrobenzene, conjugated aldehydes, arylacetylenes, and phenylpropiolates are readily reduced under mild conditions. Benzonitrile, alkylacetylenes, ketones, unconjugated aldehydes, and alkenes are not reduced.     

Controlled mono and double Heck reactions in water catalyzed by an oxime-derived palladacycle

The mono and β,β-diarylation of α,β-unsaturated carbonyl compounds with electron-deficient and electron-rich aromatic iodides in water is described. These reactions are catalyzed by the p-hydroxyacetophenone oxime-derived palladacycle 1 by controlling the stoichiometry of the aryl iodide and the alkene as well as the loading of the palladium catalyst. This one-pot protocol is performed in refluxing water and (dicyclohexyl)methylamine as base under thermal or microwave conditions and in the absence of an inert atmosphere.     

Reaction of aryl di-, tri-, or tetrabromides with arylboronic acids or alkenes in the presence of a palladium-tetraphosphine catalyst

cis,cis,cis-1,2,3,4-Tetrakis(diphenylphosphinomethyl)cyclopentane/[PdCl(C₃H₅)]₂ system catalyses the Suzuki and Heck reactions of aryl di-, tri-, or tetrabromides with a range of arylboronic acids or alkenes with moderate to high ratio substrate/catalyst in good yields. Aryl polybromides such as dibromobenzenes, 1,3,5-tribromobenzene, 1,2,4,5-tetrabromobenzene, dibromopyridines or a dibromothiophene have been successfully used. Convenient synthesis of a variety of di- and triarylated or vinylated compounds and even a 1,2,4,5-tetraarylated compound were prepared by use of this reaction.     

185-nm Photochemistry of Olefins,Strained Hydrocarbons,and Azoalkanes in Solution

The possibility to excite directly at 185 nm chromophores that absorb in the vacuum-UV has stimulated increased activity during the last decade in this field of photochemistry. Whereas photochemical reactions at λ<200 nm have been thoroughly investigated in the gas phase, only recently have intensive studies on the 185-nm photochemistry of organic compounds in solution provided new insights. Despite the high excitation energies, selective photoreactions are promoted in the short-lived singlet excited states (Rydberg photochemistry). In contrast to conventional photochemistry (λ > 220 nm), 185-nm irradiation preferentially results in intramolecular rearrangement, fragmentation, and isomerization reactions. Intermolecular radical couplings and abstractions as well as dimerizations (π, π^*-excitation) compete minimally. Besides the straightforward denitrogenation of photoresistant (“reluctant”) azoalkanes, important applications of the short-wavelength photolysis are also found in technology (photolithography) and medicine (193-nm laser). Broadening the scope of the synthetic potential of the 185-nm photochemistry, which so far has been limited to direct cis/trans isomerizations, presents a challenge for the chemist.