Bromination of pyrrolo[1,2-c]pyrimidines

Abstract

Bromination of 3,6-diphenylpyrrolo[1,2-c]pyrimidine with N-bromosuccinimide in chloroform solution yields 5- and 7-monobromo- and 5,7-dibromo-derivatives; with use of increasing amounts of N-bromosuccinimide the 5,7-dibromo-compound becomes the sole product isolated. Bromination with an excess of bromine in chloroform at room temperature rapidly yields 5,7-dibromo-3,6-diphenylpyrrolo[1,2-c]pyrimidine perbromide hydrobromide in high yield. The perbromide is easily converted into the dibromo-derivative by heat or treatment with base but in the presence of methanol or ethanol 4-alkoxy-5,7-dibromo-derivatives are obtained, together with traces of 4,5,7-tribromo-3,6-diphenylpyrrolo[1,2-c]pyrimidine. Similar treatment of 5,7-dibromo-3-methyl-6-phenylpyrrolo-[1,2-c]pyrimidine perbromide hydrobromide with ammonia yielded the 5,7-dibromo-derivative and treatment with alcohols gave the 4,5,7-tribromo-derivative. Structures of products were assigned on the basis of n.m.r. and mass spectra.