Catalyst- and Additive-Free Trifluoromethylselenolation with [Me₄N][SeCF₃]

Abstract

Environment-benign trifluoromethylselenolation of alkyl halides, electron-deficient aryl halides, diaryliodonium triflates, aryldiazonium tetrafluoroborates, and α-diazo carbonyls with the readily accessible [Me 4 N][SeCF 3 ] salt is described. A large number of structurally diversified substrates, previously trifluoromethylselenolated by metal-SeCF 3 complex or under metalmediated catalysis at elevated temperatures, were smoothly converted in this reaction at room temperature or −40 °C to room temperature without using any catalyst or additive. Yields of the reactions were comparative to or even higher than those of the early reports employing transition metal catalysts. Compared to the known means, advantages of this method include simplicity, sustainability, high speed, low reaction temperatures, mild reaction conditions, a wide range of substrates, and good functional group tolerance. This catalyst-and additive-free protocol allows a mild and straightforward synthesis of various trifluoromethyl selenoethers and demonstrates the possibility of trifluoromethylselenolation with [Me 4 N][SeCF 3 ] under greener conditions.

Fluoroalkylation of Diazo Compounds with Diverse Rfn Reagents

“…Yields of the reaction were comparative to or even higher than those employing copper catalyst. [26,38] This reaction represented the first report of transition-metal-free trifluoromethylselenolation of diazo compounds.…”

“…Later, Zhang and coworkers disclosed a transition-metalfree method for direct and efficient trifluoromethylselenolation of α-diazo carbonyls (159) with [Me 4 N][SeCF 3 ] (Scheme 25). [38] A large number of substrates were smoothly converted at À 20°C to room temperature in the presence of trifluoromethanesulfonic acid without using any additional additives to afford the corresponding α-trifluoromethylselenolated carbonyls (160) in excellent yields. Yields of the reaction were comparative to or even higher than those employing copper catalyst.…”

Markovnikov-Type Hydrotrifluoromethylchalcogenation of Unactivated Terminal Alkenes with [Me4N][XCF3] (X = S, Se) and TfOH

“…19 F NMR (471 MHz, CDCl 3 ) δ −32.0 (s, 3F). 13 C NMR (126 MHz, CDCl 3 ) δ 140.8, 128.5, 128.4, 126.2, 123.1 (q, J = 330.5 Hz), 39.4, 39.2, 33.7, 23.0 [ 43 , 46 ].…”

“…However, these reactions suffer from harsh conditions, low efficiency, poor functional group tolerance, narrow substrate scope, and/or toxicity and pre-functionalization of starting materials, which limit their practical applications [ 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ]. Notably, the direct trifluoromethylselenolation offers an elegant way to the C-SeCF 3 bond formation by using elaborate SeCF 3 reagents, such as CuSeCF 3 , Hg(SeCF 3 ) 2 , [(bpy)[Cu(SeCF 3 )] 2 , AgSeCF 3 , [Me 4 N][SeCF 3 ], ClSeCF 3 , and TsSeCF 3 [ 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 ]. Among these reagents, [Me 4 N][SeCF 3 ] is thermally stable, non-volatile, easy to handle, and readily accessible, and has become one of the most important SeCF 3 sources by far [ 48 ].…”

“…However, the homologous hydrotrifluoromethylselenolation of unactivated alkenes has not been achieved despite sulfur and selenium being the elements of the same main group [ 13 , 71 , 72 , 73 ]. Encouraged by the fact that the readily available [Me 4 N][SeCF 3 ] salt is compatible with a superacid in the reactions with α -diazo carbonyls [ 43 ], we investigated in this article the hydrotrifluoromethylselenolation of alkenes with [Me 4 N][SeCF 3 ] in the presence of a strong acid. It was pleasing to find that reactions of unactivated terminal alkenes with [Me 4 N][SeCF 3 ] and trifluoromethanesulfonic acid (TfOH) under catalyst- and additive-free conditions formed the secondary alkyl trifluoromethyl selenoethers in good yields.…”