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Although the NHC-catalyzed cyclization reactions have been well established for the synthesis of various heterocycles, the corresponding all carbon cyclization reaction for the synthesis of carbocycles is far less established. In this note, the NHC-catalyzed all carbon [4+2] cyclocondensation of α,β-unsaturated acyl chlorides and 3-alkenyloxindoles was developed to give the corresponding spirocarbocyclic oxindoles in good yield with good to high diastereoselectivities.

The enantioselective N-heterocyclic carbene-catalyzed formal [2 + 2] and [2 + 2 + 2] cycloaddition of ketenes and isothiocyanates were developed. Reaction with N-aryl isothiocyanates at room temperature favors the [2 + 2] cycloaddition, while reaction with N-benzoyl isothiocyanates at -40 °C favors the [2 + 2 + 2] cycloaddition.

The [2 + 2]-cycloaddition reaction of the aromatic isothiocyanate (III) with ketenes proceeds at room temperature with formation of 4-thioxo-2-azetidinones.

A series of spirocyclic lactones (III) is prepared with good diastereo- and enantioselectivities by reaction of isatins (I) with enals (II) in the presence of a chiral N-heterocyclic carbene.

A straightforward synthesis of optically active trifluoromethyl dihydropyranones and spirocyclic oxindole-dihydropyranones has been realized by the chiral N-heterocyclic carbenes-catalyzed cyclization of α,β-unsaturated β-methylacyl chlorides with activated trifluoromethyl ketones or isatin derivatives.