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Paper | Regular issue | Vol 26, No. 3, 1987, pp.651-674
Published online, 1st January, 1970
DOI: 10.3987/R-1987-03-0651
■ Observations on the Reactions of Isocyanoacetane Esters with Isothiocyanates and Isocyanates

Daniel M. Solomon, Razia K. Rizvi, and James J. Kaminski

*Pharmaceutical Research Division, Schering-Plogh Research Institute, Bloomfield, NJ 07003, U.S.A.

Abstract

The reactions of the metal salts of α-isocyanoacetate esters with isothiocyanates and isccyanates were examined. The effects of modifying the reaction parameters on the outcome of the reaction (Schem I) of methyl α-isocyanoacetate (1a) with phenyl isothiocyanate (2a) have been studied, thus providing enhanced understanding of the factors controlling this useful process. Specifically, the substantial influence of reaction temperature and mode of addition of reagents on the yield of main product, thiazole 3a--as well as the novel observation of the formation of imidazole 4 as a minor, but reprducible and significant, side-product--has been documented. Previausly reported oxazole formation in the low-temprature reaction of the lithio derivative of 1 with phenyl isothiocyanate (2a) was not observed in the present study; only thiazole (3a) was detected under these conditions. The reaction of isocyano ester 1a with benzyl isothiocyanate (2b) gave thiazole ester 3b or the corresponding caboxylic acid; no imidazole product was isolatd, in contrast to the result obtained with penyl isothiocyanate (2a). The previously unreported reaction of the salt of an α-isocyanoacetate ester with an isocyanate was shown to produce an amino (alkoxycarbonyl) oxazole in low yield (not optimized). No correspoding hydroxy(alkoxycarbonyl)imidazole was deteded. (See Schemes IV and VII.)