Effective [3+1+1+1] Cycloaddition to Six‐Membered Carbocycle Based on DMSO as Dual Carbon Synthon

A [3+1+1+1] cycloaddition was developed among 2‐arylpropene, ketone and DMSO in the presence of K2S2O8. 2‐arylpropene provides three carbons, ketone offers one carbon, and DMSO as dual carbon donor contributes two carbons to the six‐membered carbocycle. It gave the cyclohexene motif and spirocyclohexene skeleton. Four C−C bonds formed in this process. Both propylene and ketone could be well tolerated and give the corresponding cyclohexene or spirocyclohexene motif in useful yields. Based on the controlled experiments, a possible mechanism was proposed.