The reductive radical cyclizations of several epoxy esters have been achieved using titanocene chloride. The tether length from the initial radical to the carbonyl acceptor is the key of the reactions. We obtained products from radical cyclization onto carbonyl formate and products from formate and hydrogen elimination. The stereochemical outcome of the 5-exo radical cyclization of two diastereomers is reported. A radical cascade cyclization of an unsaturated epoxy formate is also described. (c) 2006 Elsevier Ltd. All rights reserved.
Iron-catalysed allylation–hydrogenation sequences as masked alkyl–alkyl cross-couplings
作者:Josef Bernauer、Guojiao Wu、Axel Jacobi von Wangelin
DOI:10.1039/c9ra07604b
日期:——
organomagnesium reagents (alkyl, aryl) with simple allyl acetates proceeds under mild conditions (Fe(OAc)2 or Fe(acac)2, Et2O, r.t.) to furnish various alkene and styrene derivatives. Mechanistic studies indicate the operation of a homotopic catalyst. The sequential combination of such iron-catalysed allylation with an iron-catalysed hydrogenation results in overall C(sp3)–C(sp3)-bond formation that constitutes
在温和条件下(Fe(OAc) 2或 Fe(acac) 2 , Et 2 O, rt),有机镁试剂(烷基、芳基)与简单的乙酸烯丙酯发生铁催化烯丙基化反应,得到各种烯烃和苯乙烯衍生物。机理研究表明了同伦催化剂的运作。这种铁催化烯丙基化与铁催化氢化的顺序组合导致整体C(sp 3 )–C(sp 3 )-键形成,这构成了具有挑战性的与烷基卤化物的直接交叉偶联方案的有吸引力的替代方案。
Titanocene-Promoted Eliminations on Epoxy Alcohols and Epoxy Esters
The reaction of a series of 2,3-epoxy alcohols and the corresponding formates, acetates, and benzoates promoted by Cp 2 TiCl has been studied. The different outcome of the reaction of epoxy derivatives has been rationalized in terms of mechanistically biased processes. After homolytic oxirane cleavage, four main types of reaction were found: dehydroxylation, decarboxylation, dehydrogenation, and deoxygenation