Abstract Flash vacuum pyrolysis (FVP) of 2, 7-dimethyl-2, 3: 7, 8-diepoxy-5-silaspiro [4.4]- nonane with cyclotetra-or cyclopenta-siloxanes (D 4 or D 5) leads to products which apparently result from transannular insertion of [O Si O] or an equivalent synthon inti SI O single bonds of D 4 or D 5: 2, 4, 6, 8, 10-pentasila-1, 3, 5, 7, 9, 11-hexaoxaspiro [5.5] undecane (D 2 QD 2) and 2, 4, 6, 8, 10, 12-hexasila-1, 3, 5, 7, 9, 11, 13-heptaoxaspiro [5.7 ...
