Qitao Tan

Rhodium-Catalyzed Direct ortho C–N Bond Formation of Aromatic Azo Compounds with Azides

An efficient rhodium-catalyzed regioselective C-N bond formation of azo compounds in good to excellent yields through C-H bond functionalization using azides as the nitrogen source was developed. Alkyl, aryl, and sulfonyl azides could be efficiently assembled in this reaction with excellent functional group tolerance.

Rhodium-Catalyzed Direct C–H Bond Cyanation of Arenes with Isocyanide

An efficient rhodium-catalyzed regioselective C-H bond cyanation of arenes was developed using tert-butyl isocyanide as the cyanide source. A wide range of (hetero)aryl and cycloalkenyl nitriles could be afforded with high regioselectivity and good functional group tolerance.

Pd-catalyzed oxidative annulation of hydrazides with isocyanides: synthesis of 2-amino-1,3,4-oxadiazoles.

An efficient palladium-catalyzed oxidative annulation reaction was developed through sequential isocyanide insertions into N-H and O-H bonds of hydrazides, which provides an efficient access to valuable 2-amino-1,3,4-oxadiazoles and their derivatives.

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

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.

Synthesis of Silicon and Germanium-Containing Heterosumanenes via Rhodium-Catalyzed Cyclodehydrogenation of Silicon/Germanium–Hydrogen and Carbon–Hydrogen Bonds

A three-step synthesis of C3-symmetric trisilasumanene and trigermasumanene, heteroanalogues of the π-bowl sumanene, was achieved using a threefold rhodium-catalyzed cyclodehydrogenation of Si/Ge-H and C-H bonds as the key step. Trigermasumanene was proven to adopt a planar geometry by single crystal X-ray diffraction for the first time. The optical properties were also investigated by UV-vis and fluorescence spectroscopy.

Copper-Catalyzed Synthesis of Polysubstituted Pyrroles through [3+1+1] Cycloaddition Reaction of Nitrones and Isocyanides

An efficient, copper-catalyzed [3+1+1] cycloaddition reaction was developed for the expedient synthesis of pharmacologically interesting polysubstituted pyrroles from easily available nitrones and α-acidic isocyanides. The given approach features a new mode of cycloaddition between nitrones and isocyanides with wide substrate scope, good functional group tolerance, and operational simplicity. The operando infrared spectroscopy was used for the characterization of reaction intermediates.

Cyclization of 2-Biphenylthiols to Dibenzothiophenes under PdCl2/DMSO Catalysis

A palladium-catalyzed synthesis of dibenzothiophenes from 2-biphenylthiols is described. This highly efficient reaction employs a simple PdCl2/DMSO catalytic system, in which PdCl2 is the sole metal catalyst and DMSO functions as an oxidant and solvent. This transformation has broad substrate scope and operational simplicity and proceeds in high yield. The synthetic utility was demonstrated by the facile synthesis of helical dinapthothiophene 3 and an eminent organic semiconductor DBTDT 4. Importantly, highly strained trithiasumanene 5, a buckybowl of considerable synthetic challenge, was observed under this catalytic system.