Silicon-Promoted Carbon-Carbon Bond Formation between Ketones and Allyl- or Vinylsilanes Catalyzed by Manganese(IV) Dioxide

Abstract

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=CHCH2SiMen,Ph"; m + n = 3) with various ketones (20 equiv) in the presence of Mn02 (2.0 equiv) and a drop of acetic acid at 140 °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=CHSiMe3 and CH2=CHSiMeEt2) 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 a-and the /^-electronic effects of a silicon atom promoted the C-C bond formation, while the regioselectivity came from the steric effect of the silyl group.* Recipient of the Federation of Asian Chemical Societies 1992 and 1993 Distinguished Young Chemist Award.* Academia Sinica.

Cascade Cross‐Coupling of Dienes: Photoredox and Nickel Dual Catalysis

“…Several considerations such as bond lengths, Si electronic effects, and conformation of the transition states were proposed to explain the thermodynamically more favorable 6-endo-trig cyclization. [13] Moreover, the reaction is not limited to 1,6-dienes. For example, selective 1,4-difunctionalization took place in the case of conjugated 2,3-dimethyl-1,3butadiene, giving rise to a highly substituted allylsulfone (14, 64 %).…”

“…According to Baldwin's rules, we only observed the product resulting from the six‐membered‐ring cyclization in the reaction of diallyldiphenylsilane. Several considerations such as bond lengths, Si electronic effects, and conformation of the transition states were proposed to explain the thermodynamically more favorable 6‐ endo ‐ trig cyclization . Moreover, the reaction is not limited to 1,6‐dienes.…”

Cascade Cross‐Coupling of Dienes: Photoredox and Nickel Dual Catalysis

“…Among the various bi-and tridentate ligands evaluated, only the pyridine-derived ligand class delivered substantial amounts of product 4 ( Table 1, entries 6-10). As anticipated, control experiments performed without photocatalyst, Ni catalyst, light, or degassing all delivered no product ( Table 1, entries [11][12][13][14]. With the optimized reaction conditions in hand, we first examined the scope with respect to the diene component ( Table 2).…”

Silicon-controlled Carbon-Carbon Bond Formation and Cyclization between Carbonyl Compounds and Allyltrimethylsilane

“…The corresponding spiro compounds 26 were obtained in 51% yield. Nevertheless, diethylmalonate (8) was not converted to cyclopentane derivatives 27 under the same conditions. Instead, a mixture was obtained including diethyl 2-(3-trimethylsilylpropyl)malonate (41% yield) as the major component and allylated malonate 7 (10% yield) as the byproduct.…”

“…In the course of studying silicon-controlled organic reactions, [7][8][9][10][11][12][13][14][15] we investigated the synthetic applicability of addition of ketones to allylsilanes by use of ceric ammonium nitrate (CAN), manganese(III) acetate or a mixture of CAN and manganese(III) acetate along with cupric acetate. Manipulation of the reaction conditions would enable us to accomplish monoallylation, diallylation, allylation followed by ring formation, and allylation-cyclization-elimination of carbonyl compounds.…”