Formation of cycloadducts with trans-configurated ester groups from nitrones and dimethyl maleate
作者:Hans Günter Aurich、Gerlinde Frenzen、Markus G. Rohr
DOI:10.1016/s0040-4020(01)90471-5
日期:——
there is no clue for either a non-concerted reaction course or a subsequent conversion of the cis-products to trans-product in general. Rather conversion of dimethylmaleate to dimethyl fumarate seems to be responsible for the formation of the trans-substituted cycloadducts. This conversion can be induced by small quantities of N-alkylhydroxylamine formed from slight decomposition of nitrones under the
Diastereoselective synthesis of cis-2,5-disubstituted pyrrolidine N-oxides by the retro-Cope elimination
作者:Mark C Bagley、Julie Tovey
DOI:10.1016/s0040-4039(00)01964-x
日期:2001.1
Nitrones were reacted with 3-butenylmagnesium bromide to give alkenylhydroxylamines that were cyclised by retro-Cope elimination. Heating the diastereomeric mixtures of pyrrolidine N-oxides in the absence of solvent affected a highly diastereoselective isomerisation to provide the cis-2,5-disubstituted products in excellent yield. (C) 2000 Elsevier Science Ltd. All rights reserved.
Steric effects on regioselectivity in 1.3-Dipolar cycloaddition of C,N-dialyl nitrones with acceptor-substituted alkynes
作者:Hans Günter Aurich、Michael Franzke、Hans Peter Kesselheim、Markus Rohr
DOI:10.1016/s0040-4020(01)88127-8
日期:——
The 1.3 dipolar cycloaddition of alkynes 4-6 with acyclic nitrones 1-3, 23 and 24 as well as with cyclic nitrones 27 is studied. As was found for the reaction of the aldonitrones 1-3 an increased portion of 5-regioisomers is formed with increasing steric demand of either of the two substituents, the C-alkyl substituent R2 and the N-alkyl substituent R1. Thus the conclusion is drawn that cycloaddition of 1-3 proceeds not only via transition states arising from Z-nitrones but also via transition states developing from E-nitrones, although in the ground-state the Z-isomer is favored to a considerable extent. In this context steric destabilization of the transition states is discussed qualitatively.
AURICH, HANS GUNTER;KESSELHEIM, HANS-PETER;SCHMIDT, MICHAEL, TETRAHEDRON LETT., 29,(1988) N 3, 307-310
作者:AURICH, HANS GUNTER、KESSELHEIM, HANS-PETER、SCHMIDT, MICHAEL
DOI:——
日期:——
Regio‐ and Enantioselective (3+3) Cycloaddition of Nitrones with 2‐Indolylmethanols Enabled by Cooperative Organocatalysis
作者:Tian‐Zhen Li、Si‐Jia Liu、Yu‐Wen Sun、Shuang Deng、Wei Tan、Yinchun Jiao、Yu‐Chen Zhang、Feng Shi
DOI:10.1002/anie.202011267
日期:2021.2
regiospecificity. This approach enabled not only the first organocatalytic asymmetric (3+3) cycloaddition of nitrones but also the first C3‐nucleophilic asymmetric (3+3) cycloaddition of 2‐indolylmethanols. More importantly, theoretical calculations elucidated the role of the cocatalyst HFIP in helping CPA control the reactivity and enantioselectivity of the reaction, demonstrating a new mode of cooperative catalysis