نتایج جستجو برای: unsaturated β
تعداد نتایج: 192068 فیلتر نتایج به سال:
< p>In this communication, we have reported that the Pd(OAc)2–Et3SiH-DMF system promotes the microwave-assisted chemoselective reduction of aryl α,β-unsaturated esters in good yields. The protocol affords a convenient reduction of aryl-conjugated double bonds even in presence of other functional groups like esters, phenols, and ethers.
A novel highly enantioselective one-pot dithiolation through sulfa-Michael addition/thioesterification of thiols with α,β-unsaturated N-acylated succinimides catalysed by squaramide has been developed. This organocatalysed reaction proceeded well in high to excellent yields (up to >99%) to afford useful bioactive β-sulfated thioester derivatives with high enantioselectivities (up to 96% ee).
A pyridine-catalyzed ylide cyclization affording dihydrofurans and dihydropyrroles has been developed. In the presence of a catalytic amount of pyridine and Fe(Tcpp)Cl, α-ylidene-β-diketones and α,β-unsaturated imines react with diazoacetates providing dihydrofurans and dihydropyrroles respectively, in up to 96% yield with high diastereoselectivities.
The adduct [MeO → Bpin-Bpin](-) efficiently mediates the β-boration of α,β-unsaturated imines formed in situ. The use of chiral phosphines as additives, and in particular the chiral phosphine (S)-MeBoPhoz, enables the catalytic asymmetric reaction to proceed with higher enantioselectivity than the analogue copper(I) mediated reaction.
The development of an organocatalytic one-pot cascade for the annulation of simple starting materials: α,β-unsaturated aldehydes, hydrogen peroxide, β-carbonyl compounds and NBS to furnish optically active 3-pyrones in good yield and with excellent enantioselectivity is presented. Further diversification of the obtained products is demonstrated by selective reductive transformations.
Catalytic Asymmetric Peroxidation of α,β-Unsaturated Nitroalkenes by a Bifunctional Organic Catalyst
A new enantioselective peroxidation of α,β-unsaturated nitroalkenes was realized with an easily accessible acid-base bifunctional organic catalyst derived from cinchona alkaloids. This reaction provides unprecedented easy access to optically active chiral peroxides, as illustrated by the asymmetric synthesis of β-peroxy nitro compounds.
Regioselective conjugate 1,4-trifluoromethylation of α,β-unsaturated ketones by the use of shelf-stable electrophilic trifluoromethylating reagents, S-(trifluoromethyl)diphenylsulfonium salts and copper under mild conditions is described. A wide range of acyclic aryl-aryl-enones and aryl-alkyl-enones were converted into β-trifluoromethylated ketones in low to moderate yields.
We report efficient, catalytic, asymmetric total syntheses of both (R)-fluoxetine and (S)-duloxetine from α,β-unsaturated aldehydes conducting five sequential one-pot steps (imine formation/copper mediated β-borylation/transimination/reduction/oxidation) followed by the specific ether group formation which deliver the desired products (R)-fluoxetine in 45% yield (96% ee) and (S)-duloxetine in 4...
Highly enantioselective NHC-organocatalyzed synthesis of functionalized cyclopentenes proceeding via α,β-unsaturated acyl azolium intermediates is reported. The organocascade reaction of modified enals with malonic ester derivatives having a γ-benzoyl group involves the Michael-intramolecular aldol-β-lactonization-decarboxylation sequence to deliver cyclopentenes in good yields and excellent ee...
A study exploring the chemical behavior of some dihydroxylated β-amino ester stereo- and regioisomers, derived from unsaturated cyclic β-amino acids is described. The nucleophilic fluorinations involving hydroxy-fluorine exchange of some highly functionalized alicyclic diol derivatives have been carried out in view of selective fluorination, investigating substrate dependence, neighboring group...
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