Copper-catalyzed chemoselective synthesis of 4-trifluoromethyl pyrazoles

Abstract

A copper-catalyzed chemoselective synthesis of 4-trifluoromethyl pyrazoles via cycloaddition of 2-bromo-3,3,3-trifluoropropene with N-arylsydnones has been developed.

2‐Bromo‐3,3,3‐Trifluoropropene: A Versatile Reagent for the Synthesis of Fluorinated Compounds

“…More recently, their preparation has also been reported through the cycloaddition reactions of BTP with 1,3dipolar compounds. [37][38][39][40][41] In 1994, Xu and co-workers reported the regioselective 1,3-dipolar cycloaddition of BTP with diazomethane at room temperature for several minutes, followed by dehydrobromination with an appropriate base to afford the 3-trifluoromethylpyrazole in quantitative yield. [37] Recently, Weng and co-workers developed the copper-catalyzed cycloaddition of BTP with N-arylsydnone derivatives 54 under the mild conditions (Scheme 28).…”

“…CF 3 ‐substituted pyrazoles are particularly important compounds, due to their diverse biological activities. More recently, their preparation has also been reported through the cycloaddition reactions of BTP with 1,3‐dipolar compounds [37–41] . In 1994, Xu and co‐workers reported the regioselective 1,3‐dipolar cycloaddition of BTP with diazomethane at room temperature for several minutes, followed by dehydrobromination with an appropriate base to afford the 3‐trifluoromethylpyrazole in quantitative yield [37] .…”

Synthesis of 2-trifluoromethyl chromenes via double carbonyl–ene reaction

“…As part of our continuing research interest in synthetically important heterocyclic frameworks, we have recently developed various new methods for the synthesis of trifluoromethylated heterocyclic compounds using inexpensive and readily available trifluoromethylating reagents. [25][26][27][28][29][30] In continuation of our endeavors to this research, herein we describe a catalyst-free approach for the synthesis of 2-trifluoromethyl chromenes from reaction of o-isopropenylphenols with trifluoroacetic anhydride (Scheme 1e) via sequential trifluoroacetylation and double carbonyl-ene reaction, 31 followed by elimination reaction.…”

Copper‐Catalyzed Synthesis of 5‐Aryl‐6‐(Trifluoromethyl)‐2,3‐Dihydropyrazolo[1,2‐a]Pyrazol‐1(5H)‐One

“…It has been well established that 3,3,3‐trifluoropropyne could be generated in situ from dehydrobromination of 1 under base conditions [9] . To this end, we recently reported a copper‐catalyzed chemoselective synthesis of 4‐trifluoromethyl pyrazoles from cycloaddition of N ‐arylsydnones with 1 under mild conditions [10] . We considered whether [3+2]‐cycloaddition of the azomethine imine with 1 could be an effective strategy to synthesize trifluoromethyl substituted N , N ‐bicyclic pyrazolidinone.…”