Thermal reactions of pivaloyl- and adamantoyl(tert-butylethynyl)bis(trimethylsilyl)silane with 2,3-dimethylbutadiene and diphenylacetylene

Two acylbis(silyl)silanes bearing a tert-butylethynyl group were prepared and their thermal behavior was investigated. The reaction of pivaloyl(tert-butylethynyl)bis(trimethylsilyl)silane (1a) with 2,3-dimethylbutadiene in a sealed tube at 160 °C for 24 h afforded 1-tert-butyl-1-[(tert-butylethynyl)(trimethylsiloxy)(trimethylsilyl)]silyl-3,4-dimethylcyclopent-3-ene (2a) and 2-[(tert-butylethynyl)(tert-butyltrimethylsiloxymethyl)(trimethylsilyl)]silylmethyl-3-methyl-1,3-butadiene (3a) in 45% and 13% yields, respectively. When adamantoyl(tert-butylethynyl)bis(trimethylsilyl)silane (1b) was treated under the same conditions, 1-adamantyl-1-[(tert-butylethynyl)(trimethylsiloxy)(trimethylsilyl)]silyl-3,4-dimethylcyclopent-3-ene (2b) and 2-[(adamantyltrimethylsiloxymethyl)(tert-butylethynyl)(trimethylsilyl)]silylmethyl-3-methyl-1,3-butadiene (3b) were obtained in 24% and 3% yields. The reaction of 1a with diphenylacetylene at 160 °C afforded the diastereomeric mixture, 1-tert-butyl-2,3-diphenyl-3-[(trimethylsiloxy)bis(trimethylsilyl)]silylcycloprop-1-enes (5a/5a′) in 58% combined yield. When 1b was heated with diphenylacetylene in a sealed tube at 160 °C for 24 h, 1-adamantyl-2,3-diphenyl-3-[(trimethylsiloxy)bis(trimethylsilyl)]silylcycloprop-1-enes (5b/5b′) were obtained in 54% combined yield.