A tandem coupling-ketooxygenation reaction of readily accessible enediyne-carboxylic compounds with inner alkynes has been developed that utilizes the PdCl2/CuBr2 catalytic system under an O2 atmosphere and assembles a class of isoindolinones and o-acylbenzoic acids. The two oxygen atoms are regioselectively incorporated into enediyne units at the 1- and 6-positions from atmospheric molecular oxygen and H2O, respectively, during the present process. This study uncovered a formal [4C + 2C] benzannulation-diketonization of enediynes and alkynes via a coupling and decoupling strategy.

By using an N-heterocyclic carbene catalyst bearing a hydroxyl moiety, the asymmetric formal (3 + 2) cyclization of aryl 3-bromoenals and isatins was achieved to produce a series of chiral spirooxindole-butenolides including an alkenyl-substituted compound, which underwent benzannulations with benzynes to form intriguing spirocyclic scaffolds.

The direct oxidative N-acylation reaction of primary amides with aryl/α,β-unsaturated aldehydes was achieved in the presence of azolium salt C3 and an inorganic base using 3,3',5,5'-tetra-tert-butyldiphenoquinone as the oxidant, thus providing an efficient approach for the synthesis of three types of imide compounds including N-sulfonylcarboxamides, N-sulfinylcarboxamides, and dicarboxyimides in good yield.

A tunable copper-catalyzed azide-alkyne cycloaddition (CuAAC)-initiated multicomponent reaction strategy for the construction of 3-functionalized indolin-2-ones is reported. Upon controlling the ring opening of four-membered O-heterocyclic intermediates, this unique method enables the divergent derivatization of N-protected isatins to give three-component (3-CR) and four-component (4-CR) adducts, respectively.

The spirooxindole (VIIe) is converted to a more complex spirocyclic compound by annulation with benzyne precursors.