Synthesis of Thieno[2,3-g][1,4]oxazonine and Thieno[2,3-h][1,5]oxazecine derivatives by cyanogen-bromide-induced ring expansion

Abstract

4-Phenyl-4,6,7,8,9,10-hexahydrothieno[2,3-g][1,4]oxazonine-8-carbonitrile (5a) and the analogous 4-phenyl-6,7,8,9,10,11-hexahydro-4H-thieno[2,3-h][1,5]oxazecine-9-carbonitrile (5b) were preparedin moderate yields by cyanogen bromide-induced ring expansion of the appropriate ω-(tetrahydrothieno[3,2-c]pyridyl)alkan-1-ol precursors (3). N-Methyl derivatives of these new fused medium-ring heterocyclic systems were prepared by standard methods.