Synthesis of 1,3-diaryl-3-trifluoromethylcyclopropenes by transition-metal-free reaction of 2,2,2-trifluoroacetophenone tosylhydrazones with alkynes: the effect of the trifluoromethyl groupElectronic supplementary information (ESI) available: Experimental procedures, characterization data and copies of the 1H and 13C NMR spectra for compounds 5 and 7. Computational details, energy tables and Cartesian coordinates for the stationary points represented in Fig. S1. See DOI: 10.1039/c5cc10472f

• Main Authors: Barroso, Raquel, Jiménez, Azucena, Carmen Pérez-Aguilar, M, Cabal, María-Paz, Valdés, Carlos
• Format: Journal Article
• Published: 23.02.2016
• ISSN: 1359-7345; 1364-548X
• DOI: 10.1039/c5cc10472f

1,3-Diaryl-3-trifluoromethylcyclopropenes and 2-aryl- or 2-alkyl-1,3-diaryl-3-trifluoromethylcyclopropenes are prepared in a very simple way by reaction between 1,1,1-trifluoroacetophenone tosylhydrazones and terminal or internal alkynes, respectively, in a base promoted process that does not require the presence of any metal catalyst. The essential role of the trifluoromethyl group, which enables the formation of the cyclopropenes instead of the expected pyrazoles, has been computationally investigated, suggesting the participation of a free carbene. Free carbenes, generated from trifluoroacetophenone tosylhydrazones, lead to 1,3-diaryl-3-trifluoromethylcyclopropenes by transition metal-free reactions with alkynes.