Stereoselective synthesis of diastereomeric atropisomeric lactam with various ring sizes and their structural characterization

Diastereomeric atropisomeric N-ortho-tert-butylphenyl lactams with ring sizes from four to seven were prepared with high diastereoselectivity through an aminocyclization reaction. In the case of four- and five-membered ring formation, thermodynamically stable atropisomeric lactams having a trans-relationship between the ortho-tert-butyl group and the C-4 or C-5 substituent were obtained, while in the six- and seven-membered ring-forming reaction, cis-atropisomeric lactams, kinetic controlled products, were exclusively isolated. (C) 2000 Elsevier Science Ltd.