Copper-Catalyzed Double Thiolation To Access Sulfur-Bridged Imidazopyridines with Isothiocyanate

Abstract

A copper­(I)-catalyzed sulfur-bridged dimerization of imidazopyridines has been developed using isothiocyanate as the sulfur source. This method enables a switchable synthesis of bis­(imidazo­[1,2-a]­pyridin-3-yl)­sulfanes or bis­(2-(imidazo­[1,2-a]­pyridin-2-yl)­phenyl)­sulfanes in the presence of 4-dimethylaminopyridine (DMAP) or K2CO3 when different imidazopyridines were employed. Under optimized conditions, a variety of sulfur-bridged imidazopyridines were obtained in good yields. Moreover, thiourea was proved to be the key intermediate under catalytic system A.

Recent Developments in Transition‐Metal‐Catalyzed Regioselective Functionalization of Imidazo[1, 2‐a]pyridine

“…Tian and his co‐workers in 2019 reported that sulfur atom can act as a bridge between two imidazopyridine rings where they had used isothiocyanate as the sulfur source (Scheme 48). [65] One important observation of this reaction is that depending upon the position of substituents in phenyl ring of 2‐phenylimidazo[1, 2‐ a ]pyridine and nature of base used (DMAP and K 2 CO 3 ) two types of sulfur‐bridged products were obtained. The catalytic cycle (Scheme 49) involving DMAP generates thiourea as the key intermediate.…”

Cu-Catalyzed Direct C7 Sulfonylation of Indolines with Arylsulfonyl Chlorides

“…Recently, Ackermann and Wang groups independently developed C–H chalcogenation of indolines by copper and rhodium catalysis (Scheme b) . As a continuation of our interest in Cu-catalyzed reactions and novel methods for C–H functionalization, we herein report the first example of Cu-catalyzed regioselective C7 sulfonylation of indolines with readily available and environmentally benign arylsulfuryl chlorides via the directing group strategy.…”

One-pot, microwave-assisted copper(i)-catalysed dithiocarbamation: facile introduction of dithiocarbamate on imidazopyridines

“…22 Song et al developed copper-catalysed double thiolation of imidazopyridines with isothiocyanate as the sulfur source. 23 Recently, Wang and co-workers reported an electrochemically-induced regioselective C-3 thiomethylation of imidazopyridines using thiocyanate as a sulfur source and methanol as the methylating reagent. 24 The use of DTCs as a sulfur surrogate is of interest for further research.…”