Lewis acid-catalysed reactions of 2,2,2-trichloroethyl 6-diazopenicillanate and imines: rearrangements of spiro-6-aziridine- and spiro-6-oxirane-penicillanates. X-Ray crystal structures of (3S,6′S]-2,2,2-trichloroethyl 3-[4-nitrophenyl)-1-phenylspiro[aziridine-2,6′-penicillanate] and (3S,7aR)-2,2,2-trichloroethyl 2,3,5,7a-tetrahydro-7-methoxy-2,2-dimethyl-6-(4-nitrophenyl)-5-oxopyrrolo[2,1-b]thiazole-3-carboxylate

Abstract

In the presence of boron trifluoride–diethyl ether, 6-diazopenicillanate (1) and aromatic imines react to form aziridines, thiazolo-pyrimidinones, and, in one case, an enaminopyrrolothiazole. The structure of the spiro-aziridine penicillanate (2) derived from 4-nitrobenzylideneaniline was established by X-ray diffraction. On treatment with boron trifluoride–diethyl ether, the spiro-aziridinepenicillanates rearranged to pyrrolothiazoles, and the spiro-6-oxirane penicillanate (21) gave predominantly the pyrrolothiazole (22), whose structure was confirmed by the X-ray crystal analysis of the enol ether (23).