The scope and potential of the reaction have been investigated and developed. The reaction can also be catalyzed by secondaryamines. The use of chiral cyclic amines, such as L-proline leads to optically active beta-hydroxynitrones in moderate yield and with moderate to high enantiomeric excess. The reaction mechanism was studied by kinetic measurements, intermediate and product analysis, and determination
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
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 Guenter; Eidel, Joachim; Schmidt, Michael, Chemische Berichte, 1986, vol. 119, # 1, p. 36 - 49
作者:Aurich, Hans Guenter、Eidel, Joachim、Schmidt, Michael
DOI:——
日期:——
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