Clay montmorillonite-catalysed Michael reactions of silyl ketene acetals and a silyl enol ether with α,β-unsaturated carbonyl compounds
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Abstract:
In the presence of the clay montmorillonite, silyl ketene acetals and a silyl ether react with α,β-unsaturated esters and ketones to afford the corresponding Michael adducts in the form of the silyl ketene acetals and silyl enol ethers in good yields.Keywords:
Silyl ether
Silyl enol ether
Michael reaction
A one‐pot synthesis of β‐amino α,α‐difluoro ketones without any additives was developed. Through a series of control experiments we found that water played a crucial and indispensable role. The hydrogen bond between water and fluorinated enol silyl ether had a significant impact on the addition reaction.
Silyl enol ether
Silyl ether
Enol ether
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Tricyclic
Arabinose
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Abstract The adducts (IV), generated from the silyl enol ethers (I), iodosobenzene (II), and fluoboric acid (III), react with the enol ethers (I) or (VI) to form the 1,4‐diones (V) or (VII).
Silyl enol ether
Silyl ether
Enol ether
Carbon fibers
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This study investigated a practical method for regiocontrolled synthesis of precursors of strained cyclohexynes and 1,2-cyclohexadienes, which is a one-pot procedure consisting of a rearrangement of silyl enol ether and subsequent formation of the enol triflates. Triethylsilyl enol ether, derived from cyclohexanone, was treated with a combination of LDA and t-BuOK in n-hexane/THF to encourage the migration of the silyl group to generate an α-silyl enolate. Subsequently, the α-silyl enolate was reacted with Comins’ reagent to yield the corresponding enol triflate. Finally, the α-silylated trisubstituted lithium enolate for the synthesis of 1,2-cyclohexadiene precursor was isomerized in the presence of a stoichiometric amount of water for one hour at room temperature to exclusively provide tetrasubstituted lithium enolate for the synthesis of cyclohexyne precursor in one pot.
Trifluoromethanesulfonate
Silyl enol ether
Silyl ether
Enol ether
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The catalytic asymmetric Friedel−Crafts reaction of silyl enol ethers with fluoral proceeds under Mukaiyama-aldol conditions to give silyl enol ether products. The sequential diastereoselective reactions of the resultant silyl enol ethers with electrophiles provide highly enantiopure functionalized organofluorine compounds of material and pharmaceutical interest.
Aldol reaction
Enantiopure drug
Silyl enol ether
Friedel–Crafts reaction
Enol ether
Silyl ether
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Abstract A new catalytic asymmetric tandem α‐alkenyl addition/proton shift reaction of silyl enol ethers with ketimines was serendipitously discovered in the presence of chiral N , N ′‐dioxide/Zn II complexes. The proton shift preferentially proceeded instead of a silyl shift after α‐alkenyl addition of silyl enol ether to the ketimine. A wide range of β‐amino silyl enol ethers were synthesized in high yields with good to excellent ee values. Control experiments suggest that the Mukaiyama–Mannich reaction and tandem α‐alkenyl addition/proton shift reaction are competitive reactions in the current catalytic system. The obtained β‐amino silyl enol ethers were easily transformed into β‐fluoroamines containing two vicinal tetrasubstituted carbon centers.
Silyl enol ether
Silyl ether
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An enantioselective Pd-catalyzed allylation reaction of fluorinated silyl enol ethers is reported. This reaction provides a stereoselective and efficient approach to allylated tertiary α-fluoroketones from achiral fluorinated precursors. A variety of cyclic silyl enol ether can be used, and the yields of the desired products range from 52 to 93%, and the enantiomeric excesses range from 83 to 95% ee.
Silyl enol ether
Silyl ether
Enol ether
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Abstract A new catalytic asymmetric tandem α‐alkenyl addition/proton shift reaction of silyl enol ethers with ketimines was serendipitously discovered in the presence of chiral N , N ′‐dioxide/Zn II complexes. The proton shift preferentially proceeded instead of a silyl shift after α‐alkenyl addition of silyl enol ether to the ketimine. A wide range of β‐amino silyl enol ethers were synthesized in high yields with good to excellent ee values. Control experiments suggest that the Mukaiyama–Mannich reaction and tandem α‐alkenyl addition/proton shift reaction are competitive reactions in the current catalytic system. The obtained β‐amino silyl enol ethers were easily transformed into β‐fluoroamines containing two vicinal tetrasubstituted carbon centers.
Silyl enol ether
Silyl ether
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While iminium salts generated by the oxidation of amino ketene silyl acetals show intriguing reactivities to give useful γ-oxo-α-amino esters via reactions with silyl enol ethers in good yields, new iminium salts are also prepared by the oxidation of amino silyl enol ethers. They undergo facile addition reaction with various nucleophiles to give α-amino ketone derivatives in good yields.
Iminium
Silyl ether
Silyl enol ether
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A wide range of silyl enol ethers undergo the reactions with N,N-dimethylanilines in the presence of transition metal catalysts under mild conditions to give beta-arylamino ketones. In the cases of silyl enol ethers derived from unsymmetrical ketones, regiospecific addition of carbonyl compounds was obtained at the olefinic position of silyl enol ether.
Silyl enol ether
Enol ether
Silyl ether
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