Regioselective Synthesis of Spiro-2-aminopyrimidinone Derivatives in Ionic Liquid as Green Solvent

Abstract

An interesting regioselectivity was investigated for the synthesis of spiro-2-aminopyrimidinones-5-carbonitrile (4a-e) by the multicomponent condensation of cyclic ketones (1a-d), alkyl cyanoacetates (2) and various guanidine salts (3) using 3-butyl-1-methyl-1H-imidazol-3-ium tetrafluoroborate ([BMIM][BF 4 ]) as ionic liquid. Existence of two possible potentially active centers i.e. -CN and -COOR groups in the intermediate to Michael adduct results in possibility of formation of two region-isomeric products i.e. spiro-2-aminopyrimidinones-5-carbonitrile (4a-e) or spiro-2-amino-4-imino-pyrimidin-5-carboxylic acid alkyl ester (5). High regioselectivity was displayed with exclusive formation of compound (4a-e) which was further confirmed by spectral studies.