Synthesis of 2-perfluoroalkyl-1,4-dihydropyrazolo[1,5-a][1,3,5]triazines via rearrangements of (1-perfluoroacetyl-1,4-dihydropyrazolo[5,1-c][1,2,4]triazin-4-yl)lithiums

Abstract

(3-tert-Butyl-4-R-1-R1-1,4-dihydropyrazolo[5,1-c][1,2,4]triazin-4-yl)lithiums (R = SEt, OMe, OEt; R1 = CF3CO, CF2ClCO, CF3CF2CF2CO, t-BuOCO, PhCH2) have been generated for the first time from the corresponding 1,4-dihydropyrazolo[5,1-c][1,2,4]triazines and LDA at −97 °C, and their reactivities have been investigated. It was found that in the case of perfluorinated R1 substituents, the intermediate 4-lithio species underwent an unexpected complex rearrangement with formation of 4-tert-butyl-2-R1-1,4-dihydropyrazolo[1,5-a][1,3,5]triazine-4-carboxylic acid derivatives in high yields. The structures of the starting materials and the isolated products were established on the basis of IR, NMR, high resolution mass spectra and X-ray single crystal diffraction analysis.