Oxazepines ano Thiazepines, XVII New Procedures for the Preparation of 2,3-Oihydro-1,5-Benzothiazepin-4(5H)-Ones Substituted in Position 2

2,3-Dihydro-2-aryl-1,5-benzothiazepin-4(5)-ones and 2,3-disubstituted 2,3-dihydro-1,5-benzothiazepin-4(5H)-ones have hitherto been synthesized by heating the mixture of 2-aminothiophenol and appropriately sub-stituted acrylic acids without solvent.2–7 This is a very simple and convenient method, but because of the accompanying decompositions, the yield of the reaction is generally quite poor (20 − 40%). For this reason, it seemed expedient to work out new procedures for the synthesis of these biologically important benzothiaze-pines. Preparation of 2,3-dihydro-2-phenyl-1,5-benzothia-zepin-4(5H)-one (20) was achieved by the ring enlargement of 1-thioflavanone8 but, because of the difficulties in the synthesis of the 1-thiochromanone deriva-tives in some cases, this procedure could hardly be generalized.