Chemo-divergent Cyano Group Migration: Involving Elimination and Substitution of the Key α-Thianthrenium Cyano Species

Abstract

Herein, we report a light-driven, radical-type cyano migration in the absence of a photocatalyst, enabling a chemo-divergent synthesis of (Z)-alkenyl nitriles and ketones. Trifluoromethyl thianthrenium salt (TT–CF3 +OTf–) plays multiple roles: (a) absorbing light to generate trifluoromethyl radicals to initiate the reaction and (b) forming α-thianthrenium cyano species by in situ capture of TT• +. (Z)-Alkenyl nitriles were formed through the elimination of thianthrenium salts, and aryl ketones were obtained via the nucleophilic substitution of thianthrenium salts.

Synthesis of Tetrasubstituted Alkenes by Rhodium-Catalyzed Regioselective Cyano Transfer

“…By modifying substrate steric hindrance and optimizing the transition metal catalyst, intermediate I would be generated, which subsequently undergoes CN transfer to yield a tetrasubstituted alkenitrile . At the outset of the investigations, however, it is unclear whether this strategy is implemented, as (1) the aryl-Rh species directly reacts with the malonitrile site without insertion into the alkyne and (2) competitive protonation at the nitrogen center to form cyclic products instead of β-carbon elimination to obtain cyano transfer products. ,, To realize such a design, the perfect match between a reactivity tuned transition metal catalyst and a series of readily available and structurally diversifiable dinitrile substrates is required.…”