Efficient Syntheses of New CF₃-containing Diazolopyrimidines

Abstract

A new simple and efficient way to CF 3 -containing pyrimido[1,2-a]benzimidazole and pyrazolo[1,5-a]pyrimidines, by the reaction of 1,1,1-trifluoro-4-sulfonyl-but-3-ene-2,2-dioles 1a,b with aminoheterocycles is described. The influence of reaction conditions and nature of the aminoheterocycles on regiochemistry was investigated.

A New Method for the Synthesis of 3-Thiocyanatopyrazolo[1,5-a]pyrimidines

“…As noted above, the known [ 15 , 25 , 26 , 27 , 28 , 29 , 30 ] methods of condensation of 5-aminopyrazoles differ. Therefore, we developed a more universal and effective method at this stage.…”

“…This led to the successful realization of an efficient "metal-free" C-H (An) thiocyanation of 5-aminopyrazoles under CPE and GE with the possibilities of scaling up these processes and of "chromatography-free" isolation of products 3a and 3b in pure form by (re)extraction (see Section 3.2.1 and Section 3.2.3). As noted above, the known [15,[25][26][27][28][29][30] methods of condensation of 5-aminopyrazoles differ. Therefore, we developed a more universal and effective method at this stage.…”

“…Such structures are of big interest, because pyrazolo[1,5- a ]pyrimidine is one of the synthetic analogs of purine and a scaffold for many bioactive compounds [ 24 ]. During the above studies, initial pyrazolo[1,5- a ]pyrimidines were preliminarily obtained by condensation of 5-aminopyrazoles with 1,3-dicarbonyl compounds (or their derivatives) under various conditions [ 15 , 25 , 26 , 27 , 28 , 29 , 30 ] with very moderate yields in half the cases. On the contrary, C–H (An) thiocyanation of pyrazolo[1,5- a ]pyrimidines was implemented in good and high yields in all cases [ 15 , 16 , 18 ].…”