Substituted Pyridopyrimidinones. 1. Convenient PTC Alkylation and Halogenation of 2-Hydroxy-4H-pyrido[1,2-a]pyrimidin-4-one

Alkyaltion of 2-hydroxy-4H-pyrido[1,2-a]pyrimidin-4-one (1) was investigated under solid-liquid phase transfer catalysis conditions (PTC), using tetrabutylammonium bromide and potassium carbonate. The reaction with alkyl halides led to the formation of various 2-alkoxy products, in fair yields. Reaction of compound 1 with epichlorohydrin and chloroacetonitrile, under the same PTC conditions, afforded novel O1,O3-disubstituted glycerol and oxazolo-pyridopyrimidone betain derivatives, respectively. Some 3-halo-, 3,3-dihalo and/or 2,3-dihalopyrido[1,2-a]pyrimidines were also prepared using different halogenating agents at different reaction conditions.