A New Synthetic Route for Silacyclopropanes: Reactions of a Bromosilylenoid with Olefins

Stable 1-bromo-1-silacyclopropanes were synthesized in high yields from the reaction of the stable bromotrisylsilylenoid <b>1</b> (trisyl = C­(SiMe₃)₃) with olefins such as styrene, trimethylvinylsilane, triethylvinylsilane, and dimethylphenylvinylsilane, a new synthetic route for silacyclopropanes. The structure of bromosilacyclopropane <b>5</b> was confirmed by X-ray analysis. In the presence of excess MeOH the phenyl-substituted bromosilacyclopropane <b>2</b> underwent regioselective ring opening to give the corresponding product <b>6</b>. In contrast, the reaction of silyl-substituted bromosilacyclopropane <b>5</b> with MeOH gave only the product of nucleophilic substitution at the silicon atom, 1-methoxy-1-silacyclopropane <b>7</b>, without any ring opening. Furthermore, the bromosilacyclopropane <b>2</b> extruded bromosilylene <b>8</b> through a thermal cycloreversion reaction