Studies on Cu(I)-catalyzed synthesis of simple 3-substituted 1,2-allenes and optically active 2-substituted secondary 2,3-allenols
作者:Jing Li、Chao Zhou、Chunling Fu、Shengming Ma
DOI:10.1016/j.tet.2009.02.061
日期:2009.5
methyl ethers, which would react with primary alkyl Grignard reagents under the catalysis of CuBr to afford 3-substituted 1,2-allenes or 2-substituted secondary 2,3-allenols, respectively. The reaction may be applied to the synthesis of optically active 2-substituted secondary 2,3-allenols with up to >99% ee without any protection to the free hydroxyl group in the starting 4-hydroxy-2-alkynyl methyl
Addition of Metalated 3-Alkyl-Substituted Alkoxyallenes to Imines: Preparation of Tetrasubstituted 2,5-Dihydropyrroles, Pyrrolidin-3-ones, and Pyrroles
作者:Arndt Hausherr、Hans-Ulrich Reissig
DOI:10.1002/ejoc.201800598
日期:2018.8.15
propargyl ethers. They add with low diastereoselectivity to imines and the resulting allenylamines cyclize under base or silvernitrate catalysis to give cis‐ and trans‐substituted 2,5‐dihydropyrrole derivatives. These cyclizations proceed in part stereospecifically. Subsequent reactions such as hydrolysis are also studied.
Synthesis of allenes by [2,3]-sigmatropic rearrangement of prop-2-yn-1-yl oxonium ylides formed in rhodium(II) carboxylate catalysed reactions of diazo compounds
作者:Michael P. Doyle、Vahid Bagheri、E. Elizabeth Claxton
DOI:10.1039/c39900000046
日期:——
oxophilicity of metal carbenes formed in rhodium(II) perfluorobutyrate catalysed decomposition of diazo carbonyl compounds allows selective ylide generation from methyl prop-2-yn-1-yl ethers with resulting allene production through the [2,3]-sigmatropicrearrangement.
substrate-directed regiochemistry of the cobalt-catalysed 1,4-hydrovinylation reaction is described. A variety of symmetrical and unsymmetrical 2,3-disubstituted 1,3-dienes are synthesised by ruthenium-catalysed enyne metathesis, and then reacted with a terminal alkene catalysed by cobalt(II) bromide-[1,2-bis(diphenylphosphino)ethane] [CoBr2(dppe)] under reductive conditions. The regiochemistry of the branched
Addition of lithiated methoxyallene 2 to imines provided the expected allenyl amines in good yield. These could be cyclized with base or with silver nitrate to a variety of 2,5-dihydropyrrole derivatives. Selected examples describe their conversion to pyrrolidin-3-ones or 3-methoxypyrroles. Most importantly, this [3 + 2]cyclization method could also be applied to the synthesis of 2,5-disubstituted derivatives such as 26-28 and also to the preparation of the enantiopure compound 23.