STEREOSELECTIVE NUCLEOPHILIC ADDITIONS TO THE CARBON NITROGEN DOUBLE-BOND .3. CHIRAL ACYLIMINIUM IONS

(S)-(-)-a-Phenethylamine (3), (S)-(-)-l-(2-chlorophenyl)ethylamine (4), (S)-(-)-l-(2,6-dichlorophenyl)ethylamine (5), and (S)-(-)-l-(2,3,4)5,6-pentachlorophenyl)ethylamine (6) have been incorporated into acyliminium ions of structural type 1 and 2. Five-membered ring acyliminium ion id and six-membered ring acyliminium ion 2c react with allyltrimethylsilane very stereoselectively. The configurations of the product allyl lactams were determined by chemical correlation with (S)-(+)-2-pyrrolidinone-5-acetic acid (17) and (S)-(+)-2-piperidinone-6-acetic acid (18). A transition-state model consistent with molecular orbital theory and substrate conformational preferences is proposed to account for the observed reversal of diastereoselection in the series la-d and 2a-c. © 1990, American Chemical Society. All rights reserved.