Reactions of 2,2,2-trichloroethyl 6-diazopenicillanate with aromatic aldehydes. X-Ray crystal structures of (3S,8aS)-2,2,2-trichloroethyl 2,3-dihydro-6-(4-methoxyphenyl)-2,2-dimethyl-5-oxo-5H,8aH-thiazolo[2,3-b][1,3]oxazine-3-carboxylate and (2S,5S)-2,2,2-trichloroethyl-4-formyl-2-(4-methoxyphenyl)-6,6-dimethyl-3-oxotetrahydro-1,4-thiazine-5-carboxylate

Abstract

Treatment of 6-diazopenicillanate (1) with aromatic aldehydes in the presence of Lewis acids provides spiro epoxides, oxazinones, and thiazepines, the product distribution depending upon the particular aldehyde and Lewis acid catalyst used. The structure of the oxazinone (5) derived from 4-methoxybenzaldehyde, was established by an X-ray crystal structure determination. An explanation for the formation of these products is proposed, and 6-acylpenicillanate intermediates either isolated or trapped. The epoxidation of the oxazinone (5) by m-chloroperoxybenzoic acid provided the tetrahydrothiazine (29), identified by X-ray crystallography.