Lactams. XX. Decarboxylation of Unsaturated Acids incorporated into Six-Membered Lactam Systems

Abstract

The thermal decarboxylation of some unsaturated acids (1, 5, 6, 8, and 9) incorporated into six-membered lactams was examined. Although 8 and 9 did not undergo decarboxylation when heated neat at 175-180°C and 240-245°C, respectively, for 2 h, 1, 5, and 6 were decarboxylated in 1, 1, 2, 2-tetrachloroethane at 135°C. The relative ease of the reaction was in the order of 1≥6»5. In the case of 1, the rate-decreasing effects observed on dilution and on the addition of trichloroacetic acid suggest the reaction to be a dimeric intermolecular process.