The reaction of 2,5-cyclohexadienones with methylene-tethered allenylsilane in the presence of Lewis or Brønsted acids leads to a cascade of intramolecular cyclization, yielding stereoselective tricyclic fused 6-5-4 carbocycles featuring a silyl-methylenecyclobutane ring. This transformation is notable for the diastereoselective asymmetric desymmetrization of prochiral dienones, attributed to the axial chirality of allene.