The reaction of overcrowded aryldichloromethylsilane 1 bearing a 2,6-bis[bis(trimethylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]phenyl (Bbt) group with an excess amount of XylLi or MesLi (Xyl = 2,6-xylyl, Mes = mesityl) unexpectedly afforded the corresponding dihydrobenzosilole derivative 2 together with silyl-migrated olefin 3. The generation of 2 in this reaction is most likely interpreted in terms of intermediacy of 1,2-dihydro-2-chlorosilene 4.