Synthesis of 4H-Thieno[2,3-d]azonine and Thieno[2,3-d]azecine derivatives

Abstract

Derivatives of two new thieno medium-ring heterocyclic systems have been prepared by ring degradation using cyanogen bromide-induced solvolysis of tricyclic bases. Reaction of a hexahydrothieno[2,3-glindolizine (4a) and a hexahydro-7H-thieno[3,2-a]quinolizine (4b) with cyanogen bromide and magnesium oxide under solvolytic conditions yielded derivatives of hexahydro-4H-thieno[2,3-d]azonine (5a) (6a) and octahydrothieno[2,3-d]azecine (5b) (6b), respectively. Functional group interconversions of these medium-ring systems are described, including oxidations to cyclic ketones. The 9a-phenyl derivative of (4a) reacted similarly. By contrast 10b-phenyl derivatives (10a,b) of a hexahydropyrrolo[2,1-a]isoquinoline reacted under these conditions to give medium-ring elimination products, derivatives of tetrahydro-1H-3-benzazonines.