SET and Exciplex Pathways in the Photochemical Reactions between Aromatic Ketones and Benzylsilane and Stannane Derivatives
摘要:
The photochemical reaction of alpha,alpha,alpha-trifluoroacetophenone (TFA), benzophenone, and p-cyanoacetophenone with benzyltrimethylsilane in MeCN involves hydrogen transfer from the benzylic position. Desilylation occurs as a minor process only in the case of TFA (but it increases greatly in the presence of MeOH or LiClO4). The final products result from the statistical recombination of the benzyl and ketyl radicals. Further cases of intramolecular selectivity studied are p-methylbenzyl- and p-methoxybenzyltrimethylsilane (the latter substrate undergoes mainly C-Si bond cleavage in the reaction with TFA) as well as benzyltributylstannane (only destannylation observed with all ketones). Product studies are complemented by the determination of relevant kinetic parameters through steady-state and flash-photolysis experiments. The results are explained in terms of hydrogen transfer proceeding from an exciplex and desilylation from the solvent separated radial ion pair. The latter species predominates when Delta G(et) < -10 kcal mol(-1).
Benzylsilane and benzyltin compounds were oxidized by oxovanadium(V) compound under an oxygen atmosphere to afford the corresponding aromatic aldehydes (ketones) and/or carboxylic acids. In the reaction of benzyltins, oxovanadium(V) compound can be reduced to 0.5 molar amounts. The reaction of benzylsilanes is considered to proceed via electron-transfer process. On the other hand, benzyltins may undergo
Synthesis of organotrialkylstannanes. The reaction between organic halides and hexaalkyldistannanes in the presence of palladium complexes
作者:Hormoz Azizian、Colin Eaborn、Alan Pidcock
DOI:10.1016/s0022-328x(00)84615-x
日期:1981.7
give YC6H4CH2SnR3 for (a) R = n-Bu, Y = H, m-OMe, p-OMe, m-Cl, m-CN, and m-NO2, and (b) R = Me, Y = m-Cl, m-CN, p-CN and m-NO2. These reactions are of special value as preparative procedures in cases in which Grignard or organolithium reagents cannot be used. Allyl chloride and bromide were likewise shown to react with (n-Bu3Sn)2 to give CH2CHCH2SnBu3, but n-BuCl and n-BuBr gave only a trace of n-Bu4Sn
Pyrazolo-pyridine derivatives as ligands for GABA receptors
申请人:Merck Sharp & Dohme Ltd.
公开号:US06333336B1
公开(公告)日:2001-12-25
Pyrazolo[4,3-c]pyridin-3-one derivatives substituted at the 2-position by an optionally substituted aryl or heteroaryl moiety, and having pendant substituents at the 7-position and optionally also at the 6-position, are selective ligands for GABAA receptors, particularly having high affinity for the &agr;2 and/or &agr;3 subunit, and are useful in the treatment and/or prevention of disorders of the central nervous system, including anxiety and convulsions.
Ultrasound promoted Barbier reactions and Csp3–Csp2 Stille coupling for the synthesis of diarylmethanes and substituted benzophenones
作者:Romina A. Ocampo、Liliana C. Koll、Sandra D. Mandolesi
DOI:10.1016/j.ultsonch.2012.06.014
日期:2013.1
Stille coupling under palladium catalysis between some substituted aryl compounds and benzyltributyltin compounds generated through sonicated Barbier reaction in a very short time reaction and excellent yield. The study reported below compares different methods to optimize the synthesis of usually unstable benzyltin derivatives and is another contribution to the investigation of Csp(3)-Csp(2) coupling