2-methyl-7-substituted pyrazolo[1,5-a]pyrimidines: highly regioselective synthesis and bromination

the reaction of 3-amino-5-methyl-1h-pyrazole with 1,1,1-trichloro-4-alkoxy-3-alken-2-ones [ccl3c(o)ch=c(r1)or, where r1/r = h/me, me/et, et/me, pr/et, bu/me, iso-bu/me] or β-dimethylaminovinyl ketones [r2c(o)ch=chnme2, where r2 = ph, ph-4-me, ph-4-f, ph-4-cl, ph-4-br, ph-4-no2, fur-2-yl, thien-2-yl, pyrrol-2-yl, pyrid-2-yl], in acetic acid under reflux for 16 hours, furnished highly regioselective the halomethylated pyrazolo[1,5-a]pyrimidines and aryl[heteroaryl]pyrazolo[1,5-a]pyrimidines, respectively. a protocol for the bromination reaction at the 3-position pyrazolo[1,5-a]pyrimidines also was investigated.