Magnesium bis(diisopropylamide), a useful reagent for regio- and stereoselective synthesis of kinetic silyl enol ethers

Regio- and Stereoselective Enolizations Using Calcium Bis(hexamethyldisilazide) as a Base: Synthetic, Solid-State, and Solution Studies

“…In all cases good to excellent selectivities were observed for the preferential formation of the Z -enolates. The observed selectivity is in agreement with studies using magnesium bisamide reagents, where the use of polar solvents promotes the formation of the Z -enolates . Switching the solvent medium from THF to toluene dramatically changes the selectivity of the reaction.…”

Organosilicon Reducing Reagents for Stereoselective Formations of Silyl Enol Ethers from α-Halo Carbonyl Compounds

“…Silyl enol ethers are important intermediates in organic chemistry as the synthetic equivalent of enol ether anions that are often used with Lewis acid catalysts for a variety of C–C bond-forming reactions with electrophiles. − The versatility of silyl enol ethers thus led to the development of various synthetic methodologies as exemplified in Figure . Figure a shows the well-established synthetic route, in which chlorosilanes trap metal enolates in situ generated by treating carbonyl compounds with a strong base or α-halo carbonyl compounds with metal powder, though equimolar amounts of metal salt-waste are coproduced. Other examples include metal-catalyzed reactions with hydrosilanes such as 1,4-hydrosilylation of conjugated enones (Figure b) and α-C–H bond activation of ketones followed by silylation (Figure c) .…”

Regiocontrolled Synthesis of Carbocycle-Fused Indoles via Arylation of Silyl Enol Ethers with o-Nitrophenylphenyliodonium Fluoride

“…Our method is based on the direct, regiospecific o- nitrophenylation of an enol silyl ether (Scheme ). − Subsequent reduction of the nitro group on aryl ketone 3 followed by spontaneous cyclization affords the indole products. The regiospecificity of this indole synthesis stems from the starting silyl enol ethers, which can be easily prepared in a highly or completely regiocontrolled manner by, inter alia , (a) kinetic or thermodynamic enolization of ketones, (b) Li/NH 3 reduction of enones, and (c) 1,4-addition of cuprates to enones 1 …”

“…The example in entry 3 illustrates the regiocontrol possible using the present methodology. Treatment of enol silyl ether 2b , obtained from the kinetic enolate of 2-methylcyclohexanone, with NPIF gave 3b in good yield . The regiocontrol capability of the nitrophenylation was further tested through the reaction of substrate 2c , prepared by the reaction of 2-cyclohexenone with dimethylcuprate followed by TMSCl 11a.…”