A Tin Hydride Designed To Facilitate Removal of Tin Species from Products of Stannane-Mediated Radical Reactions
作者:Derrick L. J. Clive、Jian Wang
DOI:10.1021/jo010885c
日期:2002.2.1
Bu3SnH and Ph3SnH in standard free radical reactions, but with the special characteristic that the tin-containing byproducts are easily and very largely removed by mild hydrolysis (LiOH-water-THF or TsOH-water-THF), which converts them into base-soluble (aqueous NaHCO3) materials. The performance of stannane 1 was evaluated for a range of radical reactions involving halides, selenides, Barton-McCombie
易于制备的锡烷1在标准的自由基反应中的行为与常规试剂Bu3SnH和Ph3SnH相似,但具有的特殊特征是,通过温和水解(LiOH-水-THF)可轻松且大量去除含锡副产物或TsOH-水-THF),将其转化为碱溶性(NaHCO3水溶液)。在一系列涉及卤化物,硒化物,Barton-McCombie脱氧和烯炔环化的自由基反应中,评估了锡烷1的性能。在一些情况下,通过1 H NMR监测后处理程序在去除锡中的有效性。
Adjusting the Features of Active Metallocene Ziegler Systems fot Their Potential Use as Carbon–Carbon Coupling Catalysts in Organic Synthesis
作者:Sven Thiele、Gerhard Erker
DOI:10.1002/cber.19971300210
日期:1997.2
A variety of bent metallocene dichloride/methylalumoxane catalysts, derived from the zirconocene complexes 10, 12-18, have been employed in intramolecular olefin-coupling reactions yielding monomeric or dimeric products. This was achieved by using optimized reaction conditions employing low substrate concentrations (1.0-1.8 M) and rather long reaction times. Under these particular conditions, 1,5-hexadiene
作者:Barry M. Trost、Timothy A. Grese、Dominic M. T. Chan
DOI:10.1021/ja00019a036
日期:1991.9
The potential application of [3 + 2] cycloadditions to polycarbocycle construction is considerably enhanced by the ability to perform such reactions intramolecularly. The feasibility of such processes is explored in the context of Pd-catalyzed cycloadditions of 2-[(trimethylsilyl)methyl]allyl carboxylates, wherein trimethylenemethane (TMM) precursor fragment (donor) and the electron-deficient olefin (acceptor) is joined by a tether of simple methylene groups of 3, 4, 5, and 8 members. Several versatile synthetic routes to these substrates were developed. 2-Bromo-3-(trimethylsilyl)propene proves to be a key reagent for construction of the donor portion. Acceptors bearing esters, cyano groups, and especially sulfones have been examined. The diastereoselectivity of the reaction has been explored both in terms of ring juncture and the diastereofacial selectivity with respect to an oxygen substituent at the allylic position of the acceptor. Excellent cycloadditions to give the bicyclo[3.3.0] octyl and bicyclo[4.3.0]nonyl systems are observed, whereas larger rings cannot be obtained in this series. The choice of catalyst proves critical, the most useful being either tetrakis(triphenylphosphine)palladium and DPPE or, more generally, triisopropyl phosphite and palladium acetate. The first cycloaddition of a 1,1-dialkylated TMM precursor, which fails in intermolecular cases, has been observed in this intramolecular series to give a bridgehead-substituted bicycle. A rationale for the observed diastereoselectivity is presented.