Pyrazole derivative and preparation method thereof.

Abstract

Disclosed is a method for prepg. I [R1 = H or tert-butoxycarbonyl (BOC); R2 = alkyl, aryl, aryl-alkyl, etc.; R3 = alkyl, aryl, aryl-alkyl, etc.], characterized by (1) intramol. cyclization of R3-C≡C-CONHNHBoc [R3 = same as above] in the presence of catalyst (e.g., TfOH, AuCl, AuCl3, etc.) (2) reaction of the obtained product II [R3 = same as above] with PhNTf2 and a base (3) treatment of the resulting compd. III [R3 = same as above] with R2B(OH)2, a terminal alkyne or R2SnR11R12R13 [R2 = same as above; R11-R13 = independently alkyl] in the presence of a palladium catalyst. For example, intramol. cyclization of tert-Bu 2-(3-phenylpropioloyl)hydrazinecarboxylate [PPh3AuCl, AgNTf2, CH2Cl2, room temp., 1 h, 88%], triflation [PhNTf2, i-Pr2NEt, CH2Cl2 60°, 2.5 h, 87%] and coupling reaction with phenylacetylene [Pd(PPh3)4, Et3N, DMF, 70°, 2 h] afforded compd. I [R1 = BOC; R2 = phenylethynyl; R3 = phenyl] (75% yield). [on SciFinder(R)]