A novel method of SiCl4-catalyzed/PR3-mediated β-C(sp3)−H functionalization of nitrones with aldehydes/ketones to α,β-unsaturated imines was developed. The synthesis of α,β-unsaturated imines mainly invovles deoxygenation and aldol condensation, each proceeding under a cooperation effect between Lewis acid and Lewis base. In addition, both the acidity and hydrolytic stability of the weak SiCl4 were
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
Cycloaddition of 5-substituted 1- pyrroline 1-oxide and conversion of the nitrone cycloadducts into cis-and trans- 2,5-disubstituted pyrrolidines
作者:Sk.Asrof Ali、Mohammed I.M. Wazeer
DOI:10.1016/s0040-4020(01)85751-3
日期:1993.1
carried out. The mechanism of the peracid induced ring opening reaction of isoxazolidines (5) is now firmly established. Second cycloaddition reaction of 5-substituted 1- pyrroline1-oxide (6) provides an efficient and stereoselective entry into the trans- (24) as well as cis-2,5- disubstituted pyrrolidines (28).
[reaction: see text] The first successful catalytic oxidation procedure for the chemoselective conversion of imines to nitrones is reported. The reaction is general, high yielding, and user and environmentally friendly, and furnishes a solution to the yet unanswered issue of regioselective access to nitrones by oxidation of nitrogen derivatives.
In order to make the spintrapping technique more useful in biological free radical studies, using an specially designed ESR cell for in situ electrochemical reactions, five 5-membered ring nitrones, which are analogues of 5,5-dimethyl-1-pyrroline N-oxide (DMPO), one of the most conventionally used spintraps, have been explored for their hydrogen atom (•H) adducts formation. ESR spectra consisting