A combination of polarity reversal, Diels-Alder cycloaddition and skeletal remodeling to access pyridine-fused nitrones

Solvent-controlled halohydroxylation or C3-C2 coupling of pyridinium salts through an interrupted dearomative reduction

Herein, we report an efficient and easily operable method to halohydroxylate pyridiniums through an interrupted dearomative reduction strategy. In this process, we make the most of the halide anion from the pyridinium salts by performing the reaction in DMSO without the need of external HX added. Notably, by changing the solvents from DMSO into Et2O, the bimolecular C3-C2 coupling occurs successfully.

Organophosphine as an Alkyl Transfer Shuttle for the Direct β-Alkylation of Chalcones Using Alkyl Halides

We report an efficient alkyl transfer strategy for the direct β-alkylation of chalcones using commercially available alkyl bromides as alkyl reagents. In this transformation, the ortho-phosphanyl substituent in the chalcones is crucial for controlling their reactivity and selectivity. It also serves as a reliable alkyl transfer shuttle to transform electrophilic alkyl bromides into nucleophilic alkyl species in the form of quaternary phosphonium salts and transfer the alkyl group effectively to the β-position of the chalcones. This alkyl transfer strategy can be further extended to the alkenylation of ortho-phosphanyl benzaldehydes to assemble functionalized polyenes.

Substrate-directed divergent synthesis of fused indole polycycles through Rh(II)-catalyzed cascade reactions of bis(diazo)indolin-2-ones

Herein, we report a substrate-directed diverse synthetic strategy toward two kinds of structurally intriguing fused indole polycycles through Rh(II)-catalyzed cascade reactions of bis(diazo)indolin-2-ones with enaminones. The subtle structural changes in enaminones lead to different reactivities. Cyclic enaminones produce indolo[2,3-b]indoles, whereas acyclic ones afford oxazolo[3,2-a]indoles.

Diastereoselective construction of bridged piperidines through an interrupted dearomative reduction

An interrupted dearomative reduction strategy was developed to transform planar chalcone-based pyridinium salts into structurally intriguing bridged piperidines in a completely regio- and diastereoselective manner. This reaction proceeded successfully by using cheap and easily accessible NaBH₄ as the reductant under mild conditions without exclusion of oxygen or use of special equipment.