Stereospecific additions of dimethylsilylene and diphenylsilylene to olefins

Abstract

Dimethyl-and diphenylsilylene add stereospecifically to cis-and trons-2-butene to give the corresponding siliranes. Easy additions to cyclopentene and cyclohexene indicate that the cycloadditions are cis. Opening of the siliranes by methanol also occurs in stereospecifically cis fashion.

The photochemistry of a potential diphenylsilylene precursor. Time-resolved spectroscopic studies of the reactivity of a transient vinylsilirane

“…The results of these experiments are in close correspondence with those reported by Steinmetz and Yu for the 214 nm photolysis of the related silacyclopent-3-ene derivative 1 [25], as well as with previous studies of the reactions of transient silylenes with DMB and other dienes under photochemical conditions [18,[27][28][29]. The results are consistent with the formation of DMB, SiPh 2 , and vinylsilirane 9 as the exclusive primary products of photolysis of 2, as detailed in Scheme 1.…”

“…Furthermore, we could find no evidence for the formation of the other possible (1,2)-adduct (from addition of MeOH across the Si−C 2 bond in 9), even at relatively high conversions of 2 [32]. The formation of hydrogen-migration products analogous to 6 has ample precedent in previous studies of the addition of arylsilylenes to DMB under photochemical conditions [18,[27][28][29], and has been shown to arise (along with the isomeric silacyclopent-3-ene derivative) via photoisomerization of the corresponding vinylsilirane, the main primary product of addition of silylenes to conjugated dienes [18]. Indeed, 2 and 6 are known to be the major products of photolysis of 1,1,1,3,3,3-hexamethyl-2,2-diphenyltrisilane in a 4.0 M solution of DMB in hexane, and both were attributed to secondary reactions of vinylsilirane 9 [29].…”

“…2,000 times more slowly than does the corresponding reaction of the germanium homologue of otherwise identical structure. Experimental 1 H, 13 C and 29 Si NMR spectra were recorded on Bruker AV200, DRX500 or AV600 spectrometers in deuteriochloroform solution unless otherwise noted; 1 H and 13 C spectra were referenced to the residual solvent proton and 13 C signals, respectively. 29 Si resonances were obtained via 1 H− 29 Si HMBC NMR spectroscopy using SiMe 4 as reference.…”

“…Experimental 1 H, 13 C and 29 Si NMR spectra were recorded on Bruker AV200, DRX500 or AV600 spectrometers in deuteriochloroform solution unless otherwise noted; 1 H and 13 C spectra were referenced to the residual solvent proton and 13 C signals, respectively. 29 Si resonances were obtained via 1 H− 29 Si HMBC NMR spectroscopy using SiMe 4 as reference. Low and high resolution mass spectra were obtained with a Micromass TofSpec 2E mass spectrometer using electron impact ionization (70 eV).…”

Direct Gas-Phase Kinetic Studies of Silylene Addition Reactions: SiH2 + C3H6, SiH2 + i-C4H8, and SiMe2 + C2H4. The Effects of Methyl Substitution on Strain Energies in Siliranes

“…19 In addition, the loose transition states found here (even for SiMe 2 addition) are not in conflict with long known, concerted, stereospecific nature of the silylene addition process. 16,36 RRKM Calculations, Ab Initio Calculations, and Silirane Strain Energies. The reasonable fit of the RRKM calculations to the pressure dependencies of the experimental rate constants lends weight to the conclusion that the addition reactions 3, 4, and 5 investigated here are all straightforward third-body assisted association processes.…”