The synthesis and photochemical behaviour of some annelated tropones

Abstract

The synthesis of 2-methoxy-(12), 2-methoxy-6-bromo-(13), 1-methoxy-4-methyl-(22), 3-amino-(33), 3-amino-2,4-dibromo-(35), and 3-methoxy-benzotropone (36) is reported; on irradiation of these and other benzotropones, the presence of an electron-donating group at position 1 or 3 was found to aid electrocyclization. Four new dihydrocyclobut[a]inden-7-ones (61)–(64) were thus obtained. The pyrido[b]tropones (44), (48), and (49) and the pyrido[c]tropones (59) and (60) were also synthesized; none gave electrocyclic reactions when irradiated.