Rh-Catalyzed cyclization of carbamates – synthesis of a new heterocyclic system: tetrahydro-3H-4-oxa-2-thia-2b-azacyclopropa[cd]pentalen-3-one 2,2-dioxide

Abstract

Abstract A simple method for the synthesis of five- and six-membered ring sulfone carbamates was elaborated. The method includes reaction of the corresponding starting alcohols with trichloroacetyl isocyanate following the hydrolysis of trichloroacetyl protecting group with potassium carbonate in methanol. Rh2(OAc)4 catalyzed cyclization of carbamates was investigated. It was shown that carbamates with saturated sulfone moiety tend to give products of elimination of carbamic acid (corresponding unsaturated sulfones) due to high acidity of C-H bond in α-position of sulfone ring. Unsaturated sulfone carbamate (1,1-dioxido-2,3-dihydrothiophen-3-yl carbamate) in similar reaction conditions afforded new heterocyclic system confirmed by 2D NMR: tetrahydro-3H-4-oxa-2-thia-2b-azacyclopropa[cd]pentalen-3-one 2,2-dioxide. This result can be explained by more favorable aziridination of the double C=C bond by the nitrenoid intermediate compared to the elimination pathway. In silico pharmacological profile of new heterocyclic compound was evaluated. The compound showed good ADME and acute toxicity properties and high probability level of anticancer activity for prostate carcinoma cell line PC-3.