Abstract Reduction of 6-amino-2, 3-dihydrobenzo [b] thiophen-1, 1-dioxide with DIBAL-H gave 6-amino2, 3-dihydrobenzo [b] thiophen from which the title azide was prepared; its photolysis in diethylamine-THF gave 7-diethylamino-2, 3-dihydro-8H-thieno [2, 3-d] azepine which was converted into 7-diethylamino-8H-thieno [2, 3d] azepine.