Direct Access to Thiocyano-Thioesters from Cyclic Thioacetals via Photoredox Catalysis: An Introduction of Two Functional Groups in One Pot

Abstract

The cyanation of organic compounds is an important synthetic transformation and mainly relies on a toxic CN source. Undeniably, thiocyanate salt has emerged as a very mild and environmentally benign CN source, yet its synthetic utility for cyanation is highly limited to very few types of organic compounds. Herein, we report the direct cyanation of cyclic thioacetals for accessing compounds with two different functional groups (thiocyano-thioesters) in one pot using sodium thiocyanate via photoredox catalysis. The protocol has been further extended for the direct cyanation of disulfides and diselenide to access aryl thiocyanates and aryl selenocyanate. A plausible mechanism has been proposed based on a series of control experiments, cyclic voltammetry and Stern–Volmer studies.

Transition-metal-free C–S bond cleavage and transformation of organosulfur compounds

“…In contrast to the common deprotection reaction of cyclic dithioacetals, the Bhat group recently reported a novel visible-light-induced and rhodamine 6G ( Rh6G )-catalyzed cyanation reaction of 2-aryl-1,3-dithiolanes and -dithianes using NaSCN as a cyanation source. 60 Rh6G is an organic dye that acts as a visible-light catalyst. In this photoredox catalysis, thiocyano and carbonyl groups were introduced simultaneously in one product.…”

Electrochemical synthesis of CN-substituted imidazo[1,5-a]pyridines via a cascade process using NH4SCN as both an electrolyte and a non-trivial cyanating agent

“…29 Application of the KSCN/SSA system as the [CN] source led to cyanation of electron-rich aromatics. 30 Photoredox catalysis allowed the introduction of the CN group into thiols, 31 N -aryltetrahydroisoquinolines, 32 and thioesters 33 using inorganic thiocyanates as the precursors.…”

Paired Electrolysis Enabled Cyanation of Diaryl Diselenides with KSCN Leading to Aryl Selenocyanates

“…Both thermal [ 23 , 24 , 25 , 26 , 27 ] and photocatalytic cyanation [ 28 , 29 ] with MSCN have been reported in recent years ( Scheme 1 b). Very recently, Bhat et al reported the visible-light-induced Rhodamine-6G-catalyzed cyanation of diphenyl diselenide and NaSCN by using pure oxygen as the oxidant and K 2 CO 3 as the additive ( Scheme 1 c) [ 30 ]. However, all the above-mentioned reactions require chemical oxidizing agents, photocatalysts and stoichiometric amounts of additives.…”