

CONVENIENT SYNTHESIS OF IMIDAZO[1,5-a]PYRIMIDINE DERIVATIVES AND THEIR UNUSUAL RECYCLIZATION INTO 3H-IMIDAZO[4,5-b]PYRIDINE DERIVATIVES

Abstract
New derivatives of imidazo[1,5-a]pyrimidine have been synthesized by cyclization of in situ generated 1H-imidazol-4(5)-amine with 1,3-diketones or malondialdehyde derivatives. Utilization of asymmetrical 1,3-diketones leads to the formation of a mixture of regioisomers. The discovered conversion of imidazo[1,5-a]pyrimidine core into 3H-imidazo[4,5-b]pyridine that takes place only under acidic conditions can be considered as a new version of Dimroth rearrangement involving cleavage of C–N bond and formation of C–C bond.
Keywords
1,3-diketones, 1H-imidazol-4(5)-amine; imidazo[4,5-b]pyridines; imidazo[1,5-a]pyrimidines; trifluoroacetic acid; carbonylation; Dimroth rearrangement.
Latvian Institute of Organic Synthesis - Aizkraukles iela, 21, Riga, LV-1006, Latvia - hgs@osi.lv