Isocyanide‐Induced Activation of Copper Sulfate: Direct Access to Functionalized Heteroarene Sulfonic Esters

Abstract

A novel and direct approach to alkyl/aryl heteroarene sulfonic esters using copper sulfate as the environmentally benign inorganic sulfonation reagent was first realized with the aid of isocyanide. A variety of heterocycles reacted to afford the corresponding sulfonic esters through C−H functionalization. In this transformation, the otherwise inert copper sulfate was unusually activated by an isocyanide and employed as the source of the sulfonic substituents in an unprecedented fashion. The findings suggest that an appropriate activator may liberate the chemical activities of some relatively inert inorganic salts for organic synthesis.

From Isocyanides to Iminonitriles via Silver-mediated Sequential Insertion of C(sp3)–H Bond

“…α-Iminonitriles were generally prepared using highly toxic metal cyanides with multi-steps (Gualtierotti et al., 2012, You et al., 2014, Fontaine et al., 2008, Fontaine et al., 2009, Amos et al., 2003, De Corte et al., 1987, Surmont et al., 2009, Verhé et al., 1980, Maruoka et al., 1983), whereas improved synthetic method could be achieved by isocyanide insertion into C–O bond (Tobisu et al., 2007) or C–Halo bond (Chen et al., 2016). In view of the high bioactivities of isochromans and THIQs as well as our recent development of isocyanide chemistry (Huang et al., 2014, Fang et al., 2014, Hong et al., 2017), we herein report an unprecedented silver-mediated sequential isocyanide insertion of C(sp 3 )–H bonds to afford mono- or dual α -iminonitrile substituted isochromans and THIQs, as well as aromatized phenanthridines and azapyrene (Figure 1D). The significance of the given chemistry is as follows: (1) the formation of α-iminonitriles was first realized by the synergistically cascade isocyanide insertion via C–H bond activation, where the isocyanide was used as both the crucial “CN” and “imine” sources; (2) it is the first example to construct pharmacologically relevant α-iminonitrile substituted isochromans and THIQs with quaternary carbon centers through direct C(sp 3 )–H bond isocyanide insertion; (3) a remarkable aggregation-induced emission (AIE) effect was first observed for as-prepared α-iminonitrile substituted pyrene derivative, which may open a particular area for iminonitrile applications in materials science; (4) the α-iminonitrile substituted products are valuable synthetic building blocks for facile access of pharmacologically interesting heterocycles.…”

A Rational Design of Electrochemically and Photophysically Tunable Triarylamine Luminophores by Consecutive (Pseudo‐)Four‐Component Syntheses

“…The authors have cited additional references within the Supporting Information. [28][29][30][31][32][33][34][35][36]…”

Recent Advances in Functionalization of Pyrroles and their Translational Potential

“…Different heterocycles, for example, indoles, azaindoles, pyrroles, pyrazoles, and carbazoles functioned admirably to bestow comparing sulfonic esters easily. The isocyanide is conceived to play a threefold role in the activation of conventionally inert copper sulfate: 1) reducing copper(II) to copper (I); 2) acting as a ligand; 3) facilitating the dissociation of the robust O−S bond [67] …”