An Efficient Synthesis of Benzene Fused Six-, Seven- and Eight-membered Rings Containing Nitrogen and Sulfur by Benzyne Ring Closure Reaction

3,4-Dihydro-2-H-benzo [1,4]thiazines (3a-c), 2,3,4,5-tetrahydro[b]- [1,4]thiazapines (3d-f) and 2,3,4,5-tetrahydro-2H-benzo [b][1,4]thiazocines (3g-i) were prepared by the cyclization of the respective 2-bromophenylsulfanyl derivatives of ethylamine (1a-c), propylamine (2d-f) and butylamine (2g-i).A major portion of our research for the past several years has been concerned with the use of benzyne chemistry in preparing new heterocycles.For example, we have prepared new heterocycles by nucleophilic addition to arynes possessing charged substituents, 1 by the reaction of benzyne with Barton esters, 2 and by Diels-Alder's cycloaddition reactions involving 4-haloarynes with furan, 3 selenoureas, 4 and N,N-diethylthiocarbamic acid S-o-tolyl esters. 5Recently, we turned our attention to the use of