Synthesis of Benzo[D]Thieno[2,3-G]Azecine and Benzo[D][1]Benzothieno[2,3-G]Azecine Derivatives

Abstract

Derivatives of two new diannulated azecine systems have been prepared by ring degradation of precursor bases with cyanogen -bromide-induced solvolysis. Reaction of a tetrahydro-5H-benzo[h] thieno [2,3,-a] quinolizine (5a) and a tetrahydro-7H-benzo[h][1] benzothieno [2,3-a] quinolizine (5b) with cyanogen bromide and magnesium oxide under solvolytic conditions yielded derivatives of a hexahydrobenzo [d] thieno [2,3-g] azecine (6a) and a hexahydrobenzo [d][1] benzothieno [2,3-g] azecine (6b), respectively. Functional group interconversions of these medium-ring systems were performed, including oxidations to cyclic ketones. The 5H-benzo[h] thieno [2,3-a] quinolizine and 7H-benzo[h] [l] benzothieno [2,3-a] quinolizine bases (5a) and (5b) are the first reported examples of these ring systems.