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A Readily Available Trifluoromethylation Reagent and Its Difunctionalization of Alkenes

Min Zhang, Jin-Hong Lin and Ji-Chang Xiao*

*Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China, Email: jchxiaosioc.ac.cn

M. Zhang, J.-H. Lin, J.-C. Xiao, Org. Lett., 2021, 23, 6079-6083.

DOI: 10.1021/acs.orglett.1c02146 (free Supporting Information)


Abstract

Trifluoromethylsulfonyl-pyridinium salt (TFSP) is an efficient, solid trifluoromethylation reagent, which can be readily prepared from cheap and easily available bulk industrial feedstocks. TFSP can generate a trifluoromethyl radical under photocatalysis, that can be used for azido- or cyano-trifluoromethylation reactions of alkenes.

see article for more example

proposed mechanism



General Procedure for Azidotrifluoromethylation of Alkenes

Into a 15 mL Schlenk tube were added Ir(ppy)3 (6.6 mg, 0.01 mmol, 2 mol%), FeCl3 (3.2 mg, 0.025 mmol, 5 mol%) and TFSP (404.3 mg, 1 mmol, 2 equiv.) under a N2 atmosphere. Then alkene (0.5 mmol, 1.0 equiv.), TMSN3 (115.2 mg, 1.0 mmol, 2 equiv.) and DCM (2.5 mL) were added. The resulting mixture was stirred at 35 C under irradiation of 11.5 W blue LEDs for 24 h under a N2 atmosphere. When the reaction was completed, as monitored by 19F NMR spectroscopy, the crude reaction mixture was evaporated under reduced pressure. The residue was subjected to flash column chromatography to give the final product.

General Procedure for Cyanotrifluoromethylation of Alkenes

Into a 15 mL Schlenk tube were added Ir(ppy)3 (3.3 mg, 0.005 mmol, 1 mol%), Cu2O (7.1 mg, 0.05 mmol, 10 mol%) and TFSP (303.2 mg, 0.75 mmol, 1.5 equiv.) under a N2 atmosphere. Then alkene (0.5 mmol, 1.0 equiv.), TMSCN (99.2 mg, 1.0 mmol, 2 equiv.) and CHCl3 (5 mL) were added. The resulting mixture was stirred at r.t. under irradiation of 11.5 W blue LEDs for 60 h under a N2 atmosphere. When the reaction was completed, as monitored by 19F NMR spectroscopy, the crude reaction mixture was evaporated under reduced pressure. The residue was subjected to flash column chromatography to give the final product.


Key Words

benzyl azides, trifluoromethyl alkanes, cyanation, multicomponent reactions


ID: J54-Y2021