Synthesis and spectroscopic investigations of 1,4-benzothiazepine derivatives

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Abstract
The reaction of sodium 3,4-dimethoxythiophenolate (1) with 2-bromoethylamine (2) gave 2′-aminoethyl-3,4-dimethoxy-phenyl sulfide hydrochloride (3). Ring closure of the acyl derivatives 4a–c with phosphoryl chloride furnished the 2,3-dihydro-1,4-benzothiazepines 5a–c. In a reaction competing with the cyclization, the acid amides 4 decomposed to 2′-chloroethyl-3,4-dimethoxyphenyl sulfide (7) and the corresponding nitrile. A few derivatives (8–10) of 5c were prepared. Sodium borohydride reduction of 5b, c yielded the 2,3,4,5-tetrahydro-1,3-benzothiazepines 11a, b. With substituted acetyl chlorides, compounds 5c and 10 were converted to the β-lactam derivatives 12a–f and 13, the configurations and conformations of which were determined by nmr spectroscopy; under similar reaction conditions the analogous compounds 5a, b gave the enamides 14, 15, and 16.