Herein, we describe a two-step method for the cyclopentannulation of conjugated enones using methyl 3-(terr-butyldimethylsilyloxy)-2-diazo-3-butenoate (1) as a bifunctional reagent. The enol silane and stabilized diazoalkane fiinctionalities are exploited independently in sequential Mukaiyama-Michael and diastereoselective alpha,alpha'-diketone coupling. Di-, tri-, and tetrasubstituted enones are amenable to annulation under this protocol. Overall, this chemistry is an effective surrogate for a substituted "acetone 1,3-dipole".