Facile Synthesis of 4-Acylamino and 4-Sulphonamido β-lactams

The cycloaddition reaction of trisubstituted amidines (7a–f) with acid chlorides in presence of triethylamine gave 4-acylamino and 4-sulphonamido-trans-β-lactams (9a–h) in very good yields. Similarly N,N′-diarylamidines (5a–d) on reaction with 2 equiv. of acid chlorides (8a,b) gave 4-acylamino-trans-β-lactams (10a–e) via in situ generated acylamidines followed by cycloaddition reaction.