An asymmetric synthesis of carbocyclic spiroindoline by sequential Michael reaction and [3 + 2]-cycloaddition is described. This protocol demonstrates excellent enantio- and diastereoselectivity with broad functional group tolerance. A diverse range of spiroindolines were prepared by this approach, and the products served as ideal substrates for C2 derivatization.
Cyclic amines such as 1,2,3,4-tetrahydroisoquinoline undergo regiodivergent annulation reactions with 4-nitrobutyraldehydes. These redox-neutral transformations enable the asymmetric synthesis of highly substituted polycydic ring systems in just two steps from commercial materials. The utility of this process is illustrated in a rapid synthesis of (-)-protoemetinol. Computational studies provide mechanistic insights and implicate the elimination of acetic acid from an ammonium nitronate intermediate as the rate-determining step.
Chiral cobalt(II)-salen-catalyzed Michael addition of amines to β-substituted nitroalkenes
Optically active cobalt(II) salen complexes were found to be effective Lewis acid catalysts for the enantioselective Michael addition of O-alkylhydroxylamines to nitroalkenes to afford the corresponding N-alkylhydroxyl-1,2-nitroamines in high yields and with good to high enantioselectivities. This study represents the first example of a transition-metal-catalyzed asymmetric Michael addition of amines to nitroalkenes. (C) 2014 Elsevier Ltd. All rights reserved.
A new and versatile synthesis of 5-substituted pyrrolo[2,3-d]pyrimidines
作者:Dolorès Edmont、David M Williams
DOI:10.1016/s0040-4039(00)01491-x
日期:2000.10
We have developed a new methodology for the construction of 5-substituted pyrrolo[2,3-d]pyrimidines that involves the reduction of a nitroalkane to an oxime using the reducing ability of the Sn(SR3)− species, followed by mild, acid-catalysed deoximation of the resulting adduct using Dowex-H+ resin to form an intermediate aldehyde that spontaneously cyclises to the fused pyrrole ring.
我们已经开发出了一种用于构建5取代的吡咯并[2,3- d ]嘧啶的新方法,该方法涉及利用Sn(SR 3)-的还原能力将硝基烷还原为肟,然后进行温和的,使用Dowex-H +树脂对所得加合物进行酸催化脱氧,形成中间体醛,该醛自发环化成稠合的吡咯环。