Akira Hosomi

In the presence of a stoichiometric or catalytic amount of a Lewis acidic indium(III) salt, allylsilanes reacted intramolecularly with unactivated terminal alkynes to give cyclized products in good to high yields. The fact that the reaction proceeded in a trans-addition mode suggests a reaction mechanism via electrophilic activation of the triple bond by the indium salt.

In the presence of a catalytic amount of LiCl, α-dimethylsilylesters (α-DMS-esters) 1 smoothly reacted with various aldehydes at 30 °C to give aldols in good to high yields. On the other hand, the aldol reaction with ketones was effectively promoted by MgCl₂ rather than by LiCl. α-Enones also underwent the metal chloride-promoted addition of 1 at the carbonyl carbon or β-carbon.

In the presence of LiCl, dibutylchlorostannane (Bu₂SnClH) reacted with γ-unsubstituted propargyl alcohols and ethers to give γ-stannylated allyl alcohols and ethers, respectively, with high regio- and stereoselectivity. These vinylstannane products could be successfully utilized for the Pd-catalyzed cross-coupling reaction.

In the presence of MgCl₂, dimethylsilyl (DMS) enolates 1 smoothly reacted with α-enones in DMF to form 1,5-diketones 3 in moderate to high yields. The Michael addition proceeded with moderate to high anti-diastereoselectivity.

The Et₃B-initiated reaction of γ-unsubstituted propargyl alcohols with dibutylchlorostannane (Bu₂SnClH) at low temperature gave (Z)-vinylstannanes with high regio- and stereoselectivity. The corresponding alkyl propargyl ethers also underwent regio- and stereoselective homolytic hydrostannylation with Bu₂SnClH; however, the regioselectivity was not so high as that with the propargyl alcohols.

Optically active lithium alkoxide catalyzed asymmetric reduction of imines with trimethoxhydroysilane in moderate enantioselectivity (up to 72% ee).