A chiral 1‐isopropenyl‐1‐(3‐oxopropyl)disilane derivative undergoes a type II ene reaction under Lewis acid catalyzed conditions to afford the silacyclic compound and an unexpected rearranged product with high diastereoselectivities. This rearrangement occurs through 1,2‐migration of a trimethylsilyl group. A common intermediate was proposed to explain the formation of both products.