Silicon-Promoted Carbon-Carbon Bond Formation between Ketones and Allyl- or Vinylsilanes Catalyzed by Manganese(IV) Dioxide
摘要:
The influence of silicon on the carbon-carbon bond formation was investigated by use of various silylalkenes to react with ketones. Treatment of an allylsilane (CH2=CHCH(2)SiMe(m)Ph(n); m + n 3) with various ketones (20 equiv) in the presence of MnO2 (2.0 equiv) and a drop of acetic acid at 140 degrees C in a sealed tube produced the corresponding hydrogen atom transfer adducts in 54-85% yields. Performance of the same reactions by replacement of the allylsilane with a vinylsilane (i.e., CH2=CHSiMe(3) and CH2=CHSiMeEt(2)) afforded adducts in 59-75% yields. Furthermore, reaction of diallyldimethylsilane with acetone or 3-methyl-2-butanone under the same conditions afforded 4-(3,3-dimethyl-3-silacyclohexyl)butan-2-one (81%) and 4-(3,3-dimethyl-3-silacyclohexyl)-3,3-dimethylbutan-2-one (65%), respectively. The results indicate that the alpha- and the beta-electronic effects of a silicon atom promoted the C-C bond formation, while the regioselectivity came from the steric effect of the silyl group.
Selective hydroboration of alkenes and alkynes in the presence of aldehydes and ketones
作者:George W Kabalka、Su Yu、Nan-Sheng Li
DOI:10.1139/v98-042
日期:1998.6.1
reactions of terminal alkenes in the presence of ketones or aldehydes with a variety of borane reagents have been investigated. It was found that the selective hydroboration of a terminal alkene in the presence of a ketone or an aldehyde is most efficient when dicyclohexylborane is used as the hydroborating agent. The hydroboration of olefinic ketones and olefinic aldehydes with dicyclohexylborane generates