Methyl (1aRS,7aSR)-7-formyl-1a-phenyl-1,1a-dihydroazirino[2,3-b]benzo[e][1,4]thiazine-7a(7H)-carboxylate

The first representative of the aziridine-fused benzo[e][1,4]thiazine series was synthesized from methyl 2-bromo-2-phenyl-2H-azirine-2-carboxylate and benzo[d]thiazole in 74% yield. The reaction proceeds via the SN2′-SN2′-cascade to form the azirinylthiazolium salt followed by a water-induced thiazole ring expansion. The structure of the title compound was established based on 1H, 13C, 2D NMR spectroscopy and high-resolution mass spectrometry, and unambiguously confirmed by X-ray diffraction analysis.