Transformations of tetrahydro-1,4-benzoxazepines and tetrahydro-1,4- benzothiazepines under the action of alkynes. First example of the synthesis of tetrahydro-1,4-benzothiazonine-6-carboxylate

It was shown that 2,3,4,5-tetrahydro-1,4-benzoxazepines were cleaved at the N-C(5) bond under the action of activated alkynes in methanol, forming o-(methoxyethyl)- and o-(methoxybenzyl)-phenyl(aminoethyl) ethers. The cleavage rate depended on the electronic effects of the substituents at the C-5 atom. Thiazepine ring expansion in tetrahydro-1,4-benzothiazepine was achieved for the first time via reaction with methyl propiolate to give a benzothiazonine. © 2013 Springer Science+Business Media New York.