Collaborative Activation of Trifluoroacetyl Diazoester by a Lewis Acid and Base for the Synthesis of Polysubstituted 4-Trifluoromethylpyrazoles.

A Lewis acid- and base-co-mediated cyclization of trifluoroacetyl diazoester and ketones is developed. Cooperative functioning of the Lewis acid and Lewis base with trifluoroacetyl diazoester results in increased electrophilicity of terminal nitrogen atoms. The reaction affords polysubstituted 4-trifluoromethyl pyrazoles in moderate to excellent yields.

Base-Mediated Tunable Synthesis of 2-Trifluoromethylated Furans and Dihydrofuranols: Extraordinary Stable in Sulfuric Acid.

2-Trifluoromethylated furans and dihydrofuranols were tunably synthesized from the cyclization of ß-ketonitriles with 3-bromo-1,1,1-trifluoroacetone mediated by bases. In addition, dehydration of dihydrofuranol compounds with concentrated sulfuric acid gave another 2-(trifluoromethyl)furans isomer. The developed methodology exhibits an excellent functional group tolerance for both aromatic and aliphatic ß-ketonitriles.

Silver-Catalyzed Regioselective Synthesis of Highly Substituted 2-Trifluoromethyl Pyrroles.

An efficient and regioselective synthesis of highly substituted 2-trifluoromethyl pyrrole derivatives via silver-catalyzed cyclization of vinyl azides with ethyl 4,4,4-trifluoro-3-oxobutanoate is reported. Various α-(heteo)aryl, alkyl, ß-aryl, as well as α,ß-disubstituted vinyl azides, participate in this transformation. The reaction mechanism likely involves the addition of in situ generated 2H-azirine to the diketone species, followed by intramolecular addition, N-C1 cleavage, and elimination.