Unexpected regiospecific reactivity of a substituted phthalic anhydride

Regioselective nucleophilic addition at C1 of anhydride 7 by a range of nucleophiles occurs to produce amide, ester and thioester derivatives 8–15 (60–99%). The increased electrophilic reactivity of the C1 carbonyl group of anhydride 7 is supported by a competition experiment with phthalic anhydride. Unexpected formation of lactams 18 and 19 from amides 12 and 13 was shown to proceed via the lactamols 16 and 17 and could be controlled by the reaction conditions. The solid-state structure of 19 is reported.