Silicon-Carbon Unsaturated Compounds. 53. Thermal Reactions of Acylpolysilanes

Thermolysis of six acylpolysilanes, acetyl-, isopropionyl-, pivaloyl-, adamantoyl-, benzoyl-, and mesitoyltris(trimethylsily1)silane (1–6), in the presence or absence of a trapping agent has been examined. Thermolysis of 1 in benzene at 150 °C gave 1,1,1,4,4,4-hexamethyl-2-[1-(trimethylsiloxy)ethenyl]-3-[l-(trimethylsiloxy)ethyl]-2,3-bis(trimethylsilyl)tetrasilane (7). Similar treatment of 2 at 140 °C produced 1,1,1,3,3,3-hexamethyl-2-[l-isopropyl-3-methyl-2-(trimethylsiloxyl)-l-butenyl]-2-(trimethylsiloxy)trisilane (9), along with a dimer (8), analogous to 7. Thermolysis of 3 and 4 under the same conditions afforded no products, but the starting compounds were recovered quantitatively, while 5 and 6 yielded mainly nonvolatile substances. The thermolysis of 1–4 in the presence of 2,3-dimethyl-1,3-butadiene produced both [2 + 4] cycloadducts and ene adducts arising from the reaction of silenes generated thermally from 1–4 with butadiene, while 5 and 6 gave only [2 + 4] cycloadducts. With α-methylstyrene, 1–6 afforded only adducts derived from the ene reaction of the silenes with olefin. The thermolysis of 1–4 with styrene produced the respective [2 + 2] cycloadducts composed of a mixture of cis and trans isomers. Similar reactions of 5 and 6 with styrene gave only [2 + 2] cycloadducts with cis configuration.