Triazolo[4, 5-d]pyrimidines. XI. Halogen-Metal Exchange Reaction of 5-Halo-3H-1, 2, 3-triazolo-[4, 5-d]pyrimidines with Butyllithium

Abstract

The amino group at the 5-position on the 3H-1, 2, 3-triazolo[4, 5-d]pyrimidine (triazolopyrimidine) ring was converted into a halogen atom by treatment with isopentyl nitrite in halomethanes in satisfactory yields.The 5-halotriazolopyrimidines not having a substituent at the 7-position reacted with butyllithium to give 7-butyl-6, 7-dihydro-3-phenyl-3H-1, 2, 3-triazolo[4, 5-d]pyrimidines by addition of butyllithium across the C⁷, N⁶-double bond. In the case of the 7-substituted 5-halotriazolopyrimidines, the halogen-metal exchange reaction proceeded and the resultant 5-lithio compound reacted with electrophiles to give the 5-substituted triazolopyrimidines.