H. Sprecher, S. Pletscher, Manuel Möri
2010
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0
Influential Citations
14
Citations
Journal
Helvetica Chimica Acta
Abstract
A number of N-acryloyl-, N-crotonoyl-, N-(3,3,3-trifluorocrotonoyl)-, N-cinnamoyl-, and N-(3-nitroacryloyl)-4-isopropyl- or -4-phenyl-oxazolidin-2-ones with geminal diphenyl substitution, i.e., 7–15, have been prepared and used for conjugate additions of organocuprate reagents (Me, iPr, Ph, 4-MeOPh) in the β-carbonyl (Table 2) and in the α-carbonyl position (NO2-derivative 11 in Scheme 3). The yields and diastereoselectivities are compared with previously tested enoyl-oxazolidinones (Table 2). Highest diastereoselectivities (>90%) are always observed with the 4-Ph derivatives (Hruby effect). Nitroacryloyl-oxazolidinones and a corresponding phenylmenthol ester undergo less diastereoselective additions (Scheme 3). A 3-(1-methylethyl)-5,5-diphenyloxazolidin-2-one (DIOZ)-derived Li2-enolate-nitronate was also tested for α-carbonyl alkylation (Scheme 4). The X-ray crystal structures of three acryloyl-oxazolidinones and of four adducts are described (Tables 1 and 3), and they serve for configurational assignments and description of the stereochemical courses of the additions and alkylation. Possible applications of the nitro compounds for the preparation of β2-amino acids are discussed (Scheme 2).