Electrochemical Synthesis of gem‐Difluoro‐ and γ‐Fluoro‐Allyl Boronates and Silanes

Abstract

The electrochemical synthesis of fluorinated allyl silanes and boronates was disclosed. The addition of electrogenerated boryl or silyl radicals onto many α‐trifluoromethyl or α‐difluoromethylstyrenes in an undivided cell allowed the formation of a large panel of synthetically useful gem‐difluoro and γ‐fluoroallyl boronates and silanes (64 examples, from 31 % to 95 % yield). In addition, a scale up of the reactions under continuous flow was showcased using an electrochemical reactor with promising volumetric productivity (688 g.L−1.h−1 and 496 g.L−1.h−1). Moreover, the synthetic utility of these building blocks was highlighted through versatile transformations. Finally, plausible reaction mechanisms were suggested to explain the formation of the products.

Organoelectrophotocatalytic C–H Silylation of Heteroarenes

“…Organic electrosynthesis has emerged as an attractive and straightforward approach in dehydrogenation cross-coupling with hydrogen as the only byproduct . Electrochemical generation of silyl radicals has been reported via a stoichiometric NHPI-promoted HAT process and the cleavage of a Si–Cl bond or Si–B bond . However, the silyl radicals are easily further oxidized to silyl cations under electrooxidative conditions, in which the latter can be used to synthesize silanols and silicon-containing cyclic compounds .…”

Electrochemical synthesis and transformation of organoboron compounds

“…22 The proposed mechanism starts with the oxi- 23 An electrochemical defluoroborylation reaction between α-tri(di)fluoromethyl styrenes and B 2 pin 2 to afford gemdifluoro and γ-fluoroallyl boronate esters was disclosed by Poisson and co-workers (Scheme 9a). 24 This scalable transformation provided an efficient synthetic method for useful fluorinated allyl boronate esters. Very recently, the electrochemical hydroboration of electron-deficient alkenes and allenoates with B 2 pin 2 has also been achieved by the same group (Scheme 9b).…”

Metal‐Free Defluoroborylation of 3,3‐Difluoropropenes

“…A number of studies have already been reported on the metal‐catalyzed S N 2′ defluoroborylation of fluoroallyl groups using B 2 pin 2 (Scheme 1C) [11] . Recently, an electrochemical method has also been described [12] . Herein, we disclose the first metal‐free defluorinative borylation of 3,3‐difluoropropenes using a combination of B 2 pin 2 and fluoride source to provide β‐boryl‐substituted monofluoroalkenes (Scheme 1D).…”