5,7-DICHLOROPYRAZOLO[1,5-A]PYRIMIDINE

5,7-Dichloropyrazolo[1,5-a]pyrimidine is a pharmaceutical intermediate compound that can be used in a palladium-catalysed pharmaceutical synthesis cross-coupling reaction. 2,4-Dichloroquinoline reacts with benzylzinc and phenylzinc reagents in the presence of catalytic quantities of palladium complexes to yield only α-substituted products.2,4-Dichloroquinolines have been found to react with benzylzinc and phenylzinc reagents in catalytic amounts of palladium compounds to produce only α-substituted products. LiCl was found to be an effective additive for γ-selective coupling reactions. These α- or γ-selective coupling conditions are applicable to the reaction of 5,7-Dichloropyrazolo[1,5-a]pyrimidine and biphenylmethyl zinc reagents in the synthesis of angiotensin II receptor antagonists. This regioselectivity should be generally applicable to other α,γ-dichloropyrazine systems^[1].

[1] TAKESHI SHIOTA; Teruo Y. Regioselective Reactions of Organozinc Reagents with 2,4-Dichloroquinoline and 5,7-Dichloropyrazolo[1,5-a]pyrimidine[J]. ACS Applied Electronic Materials, 1999. DOI:10.1021/jo981423a.