Use of chiral B(III) complexes in the cycloaddition of C,N-diphenylnitrone to tert-butyl vinyl ether
摘要:
The 1,3-dipolar cycloaddition of C,N-diphenylnitrone to tert-butyl vinyl ether in the presence of several chiral B(III) complexes which incorporate different bidentate ligands has been investigated. The use of these B(III) species reverses the endo/exo diastereoselectivity in relation to the uncatalysed reaction, giving trans cycloadducts as major products. Some of the catalysts gave very fast and high yielding reactions, but the enantioselectivities were only low to moderate. (C) 2000 Elsevier Science Ltd. All rights reserved.
The attempted stereoselective synthesis of chiral 2,2′-biindoline
作者:Mary J. Gresser、Steven M. Wales、Paul A. Keller
DOI:10.1016/j.tet.2010.06.035
日期:2010.8
The attempted first stereoselective synthesis of 2,2'-biindoline using a metathesis-Sharpless asymmetric dihydroxylation strategy results in the synthesis of the heterocycle in poor to modest stereoselectivity. Attempts to improve the ee by varying the heteroatom protecting groups in key intermediates did not enhance the outcome of the Sharpless AD reaction. Therefore a limitation of this AD reaction is the use of 1,4-substituted but-2-enes where these substituents are ortho-substituted aromatics. Crown Copyright (C) 2010 Published by Elsevier Ltd. All rights reserved.
Synthesis of new enantiomerically pure monoketals of p-benzoquinone with C2-symmetry
作者:Pedro de March、Marta Figueredo、Josep Font、Jordi Medrano
DOI:10.1016/s0040-4020(99)00400-7
日期:1999.6
Several new monoketals of p-benzoquinone with the structure of 1,3-dioxaspiro[4.5]deca-6,9-dien-8-one have been synthesised in enantiopure form by the straightforward reaction of the quinone with secondary C-2-symmetric 1,2-diols. The preparation of two new enantiopure C-2-1,2-glycolsis also reported. (C) 1999 Elsevier Science Ltd. All rights reserved.
Use of chiral B(III) complexes in the cycloaddition of C,N-diphenylnitrone to tert-butyl vinyl ether
作者:Pau Bayón、Pedro de March、Marta Figueredo、Josep Font、Jordi Medrano
DOI:10.1016/s0957-4166(00)00405-5
日期:2000.11
The 1,3-dipolar cycloaddition of C,N-diphenylnitrone to tert-butyl vinyl ether in the presence of several chiral B(III) complexes which incorporate different bidentate ligands has been investigated. The use of these B(III) species reverses the endo/exo diastereoselectivity in relation to the uncatalysed reaction, giving trans cycloadducts as major products. Some of the catalysts gave very fast and high yielding reactions, but the enantioselectivities were only low to moderate. (C) 2000 Elsevier Science Ltd. All rights reserved.
Ring-opening reactions of cis- and trans-2,3-bis(4-methoxybenzyl)oxirane: competition between assistance by and migration of anti aryl group