22,-Dimethyl-4-phenyloxazoline and 2,2-dimethyl-4,5-diphenylimidazolidine as new chiral auxiliaries. Applications to asymmetric nitrile oxide cycloadditions
Asymmetric dipolar cycloadditions of a nitrileoxide to the acrylamide derivatives of two new chiralauxiliaries, (R)-2,2-dimethyl-4-phenyloxazolidines and (S,S)-2,2-dimethyl-4,5-diphenylimidazolidine, show satisfactorily high diastereoselectivities (up to 91%).
Chiral auxiliary control of tacticity in free radical polymerization
作者:Ned A. Porter、Timothy R. Allen、Robert A. Breyer
DOI:10.1021/ja00046a011
日期:1992.9
Chiral oxazolidine acrylamides undergo stereocontrolled free radicalpolymerization. Remarkably high degrees of tacticity have been demonstrated in the polymerization of acrylamides with these chiral auxiliaries that are derived from valine, phenylglycine, and tert-leucine. The polyacrylamides formed in these polymerizations can be converted to poly(acrylic acid), P(AA), and poly(methyl acrylate),
Racemic and asymmetric cobalt-catalysed reductive aldol couplings of α,β-unsaturated amides with ketones
作者:Ralph J.R. Lumby、Pekka M. Joensuu、Hon Wai Lam
DOI:10.1016/j.tet.2008.06.022
日期:2008.8
In the presence of diethylzinc as a stoichiometric reductant, substoichiometric quantities of an appropriate cobalt source catalyse diastereoselective reductive aldol coupling reactions of α,β-unsaturatedamides with ketones. The use of a readily available oxazolidine as a chiral auxiliary imparts high levels of asymmetric induction in these reactions.
to access 1,2-diamines incorporating perfluorinated groups, the Michael-like addition of nitrogen nucleophiles to 3,3,3-trifluoro-1-nitropropene has been investigated using racemic and optically pure nucleophiles such as amines, amides, oxazolidin(on)es, and thiazolidin(on)es. Complete diastereoselectivity of the addition was achieved with 4-phenylthiazolidine-2-thione.
A solution of potassium tert-butoxide in THF was shown to remarkably enhance the base-induced Sommelet-Hauser rearrangement of N-benzylic amino acid-derived ammonium ylides. (C) 2010 Elsevier Ltd. All rights reserved.