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The first CuI-catalyzed decarboxylative thiolation of terminal alkyne-substituted cyclic carbonates/carbamates to access allenes has been developed. A wide range of hydroxymethyl- and aminomethyl-containing allenyl thioethers were smoothly obtained in good to excellent yields under mild conditions. The copper-allenylidene intermediate among the process is crucial to the decarboxylative thiolation reaction. This method opens up a new channel to access allenyl thioether compounds.

An efficient decarboxylative [3 + 2] annulation reaction of ethynylethylene carbonates and azlactones has been developed with a copper salt as catalyst. This practical methodology gives access to a diverse library of γ-butyrolactones bearing α,β-two vicinal quaternary carbon centers in good to high yields with good levels of diastereoselectivities (up to 98% yield, >95:5 dr). Preliminary trials on enantioselective variant with a chiral PyBox ligand provided chiral products in up to 71% ee. This synthetic method features mild reaction conditions, broad functional group tolerance, large-scale synthesis, and versatile products transformation. A plausible catalytic cycle for the protocol is proposed based on previous related studies and our experimental observations.

N-2,2,2-Trifluoroethylisatin ketimines with β-trifluoromethyl enones, 3-trifluoroethylidene oxindole, and 3-trifluoroethylidene benzofuranone can undergo asymmetric [3 + 2] cycloaddition, catalyzed by chiral bifunctional squaramide-tertiary amine catalysts, affording a wide spectrum of 3,2′-pyrrolidinyl spirooxindoles. The significance of this protocol is highlighted by its extremely high efficiency in the construction of the structurally diverse spirocyclic oxindoles, bearing a vicinally bis(trifluoromethyl)-substituted pyrrolidine moiety, including four contiguous stereocenters, in high yields with excellent stereocontrol.

Reported here is a highly enantioselective homoenolate Michael addition/esterification sequence of cyclohexadienone-tethered enals via N-heterocyclic carbene (NHC) catalysis, affording the enantiopure cis-hydrobenzofurans, cis-hydroindoles, and cis-hydroindenes. The NHC catalyst bearing a nitro group greatly enhances the stereocontrol, and a bulky N-aryl substituent of the triazolium salt in the catalyst is helpful for inhibiting the further aldol condensation after homoenolate Michael addition. The utility of this protocol is highlighted by a gram-scale experiment and versatile downstream transformations.