An efficient and atom-economical methodology for the synthesis of multi-substituted carbazoles starting from α-aryl ketones and ynones under mild reaction conditions has been developed. This process goes through Cs2CO3 promoted C-C σ-bond activation of α-aryl ketones followed by highly selective C-H bond activations and C-C bond fragmentations in a one-pot operation.

A practical route from oxetane or thietane to γ-(thio)butyrolactone via solvated-proton-assisted cobalt-catalyzed carbonylative ring expansion under syngas atmosphere has been established. A wide variety of γ-(thio)butyrolactones can be afforded in good to excellent yields. The versatility of this method has been well demonstrated in the synthesis of intermediates towards the natural product Arctigenin as well as the pharmaceuticals Baclofen and Montelukast. The observed promoting effect of glycol ether solvent has been rationally interpreted.

The transition-metal-free insertion of isolated alkynes into carbon-carbon σ-bonds of unstrained cyclic β-dicarbonyl compounds has been reported. These tandem reactions offer an efficient synthesis of medium-sized ring or fused-ring compounds through ring expansion. The methodology has the potential to be widely used throughout organic synthesis due to the easily accessible starting materials and mild reaction conditions.

A novel ring expansion reaction of indene-1,3-dione with alkynyl ketones under transition-metal-free conditions has been developed. This process offers an efficient and direct way to synthesize benzoannulated seven-membered rings or fused-ring compounds through C-C σ-bond activation. Notable features of the procedure include easily accessible starting materials, good functional group tolerance, and high atom economy.

Base‐promoted insertion reactions of alkynes into the C–C σ‐bonds of α‐cyano ketones were established to construct highly functionalized conjugated olefins or chromone derivatives via transition metal‐free tandem reactions. These reactions are initialized through the nucleophilic attack of α‐cyano ketones to alkynones followed by intramolecular nucleophilic addition/ring‐opening to furnish the cyano‐containing alkenes. In the cases of alkynones bearing an ortho‐halide‐substituted aryl ring, a further C–O bond coupling reaction occurs to afford chromone derivatives in good to high yields. Various alkynones bearing alkyl or aryl substituents were compatible in the reaction. This reaction has the potential to become a general synthetic protocol for the preparation of cyano‐substituted olefins and chromones due to the abundance of easily accessible starting materials possessing diverse substituent groups.magnified image

Transition-metal free insertions of alkynes into carbon-carbon σ-bonds of ethanones have been reported. These tandem reactions offer an efficient synthesis of hydroxydienones and multi-substituted chromones. This is the first example of base-promoted insertion reactions of isolated carbon-carbon triple bonds into carbon-carbon σ-bonds with active methylene compounds bearing only one electron-withdrawing group.

A novel Pd‐catalyzed method for the synthesis of indolo[1, 2‐f]phenanthridines from 2‐bromo‐2′‐iodo‐1,1′‐biphenyl and indole derivatives has been reported. The reaction involves direct N−H and C2‐H arylation of indole. This Pd‐catalyzed double arylation provides a useful route to synthesize indolo[1, 2‐f]phenanthridine derivatives from simple and readily accessible starting materials.

An efficient tandem Au(i)/TsOH-catalyzed reaction of enaminones with diazo compounds for the synthesis of pyrroloquinolinone derivatives under mild reaction conditions has been developed. This methodology was realized by relay actions of Au and TsOH in a one-pot multistep manner. Initially, the Au-catalyzed reaction of enaminones with diazo compounds affords chemo- and diastereoselective C(sp(2))-H functionalized products, which then undergo subsequent intramolecular cyclization/rearrangement to give pyrroloquinolinone derivatives under the catalysis of TsOH.