Trichloroisocyanuric acid mediated one-pot synthesis of 3,5-diarylisoxazoles from α,β-unsaturated ketones

A facile one-pot synthesis of 3,5-diarylisoxazoles from α,β-unsaturated ketones and hydroxylamine hydrochloride is reported. The reaction is efficiently promoted by trichloroisocyanuric acid (TCCA) to afford the desired products, mostly in high yields and in relatively short time. The mild nature of the synthesis and short reaction time are notable advantages of the developed protocol. This protocol is effective towards various substrates having different functionalities.     

Lipase-catalyzed kinetic resolution of α,β-unsaturated α′-acetoxy ketones

The lipase-catalyzed kinetic resolutions of the α,β-unsaturated α′-acetoxy ketones 3a,b have been investigated. Of the lipases examined, CAL-B from Candida antarctica (fraction B) has been shown to be an efficient biocatalyst, which may be used effectively in preparative scale reactions.     

Enantioselective organocatalytic conjugate addition of α-nitroacetate to α,β-unsaturated ketones in water

The catalytic enantioselective conjugate addition reaction of α-nitroacetate to α,β-unsaturated ketones promoted by chiral bifunctional organocatalysts is described. The treatment of α-nitroacetate to α,β-unsaturated ketones under aqueous-phase reaction conditions afforded the corresponding Michael adducts with high enantioselectivity. The conjugate addition adducts are easily converted to chiral δ-keto nitroalkanes and δ-keto esters.     

Cobalt-catalyzed conjugate addition of silylacetylenes to α,β-unsaturated ketones

Catalytic addition of silylacetylenes to α,β-unsaturated ketones proceeded in the presence of a cobalt complex coordinated with a bisphosphine ligand to give high yields of β-alkynylketones.     

DABCO catalyzed dimerization of α,β-unsaturated ketones and nitriles

α,β-Unsaturated ketones dimerize in the presence of catalytic amount of 1,4-diazabicyclo[2.2.2]octane(DABCO) to produce the corresponding 2-methylene-1,5-diketones in good yields. Acrylonitrile provides the corresponding dimerized product.     

Reaction of α,β-unsaturated trifluoromethyl ketones with cyclic enamines

The reactions of ,-unsaturated trifluoromethyl ketones containing aromatic and heteroaromatic substituents with 1-morpholinocyclopentene, 1-morpholinocyclohexene, and 1-methyl-4-morpholino-1,2,5,6-tetrahydropyridine were studied. The reactions proceeded stereospecifically to give the corresponding bicyclo[3.2.1]octane, bicyclo[3.3.1]nonane, and azabicyclo[3.3.1]nonane derivatives.     

Reaction of unsymmetrical α,β-unsaturated ketones with thiobarbituric acid

Carbocyclization of unsymmetrical 1,5-diarylpenta-1,4-dien-3-ones with thiobarbituric acid afforded previously unknown 7,11-diaryl-3-thioxo-2,4-diazaspiro[5.5]undecane-1,5,9-triones with high regio- and stereoselectivity. The same spiro compounds were also synthesized by three-component condensation of thiobarbituric acid with the corresponding aromatic aldehydes and 4-arylbut-3-en-2-ones.     

The Darzens condensation of α,β-unsaturated aldehydes and ketones

The one-pot Darzens condensation of α,β-unsaturated aldehydes and ketones with enolates of an α-bromo ester or ketone is described.     

Addition of esters of nitroacetic acid to α,β-unsaturated ketones

Summary The addition reaction of esters of nitroacetic acid to, -unsaturated ketones was studied, and new esters of ketonitroacids were prepared.     

Reaction of α,β-unsaturated trifluoromethyl ketones with ethyl cyanoacetate

β-Aryl-substituted α,β-unsaturated trifluoromethyl ketones react with ethyl cyanoacetate to give the corresponding Michael addition products, ethyl 3-aryl-2-cyano-6,6,6-trifluoro-5-oxohexanoates, which are formed as mixtures of two diastereoisomers. The reaction time and product yield depend on electron-donating properties of the substituent in the initial ketone. The reaction is not accompanied by intramolecular cyclization of the Michael adducts.     

Amino-acid-mediated epoxidation of α,β-unsaturated ketones by hydrogen peroxide in aqueous media

Amino acids, such as arginine and lysine, can be used as an efficient catalyst in the epoxidation of α,β-unsaturated ketones with aqueous hydrogen peroxide. Up to >99% conversion was obtained in the reaction toward 11 α,β-unsaturated ketones.     

The cation exchange resin-promoted coupling of alkynes with aldehydes: one-pot synthesis of α,β-unsaturated ketones

Alkynes undergo smooth coupling with aldehydes in the presence of Amberlyst-15^® at room temperature to produce the corresponding α,β-unsaturated ketones in high yields with E-geometry. The use of an inexpensive, readily available, and recyclable cation exchange resin makes this method quite simple and convenient.     

Two-carbon homologation of aldehydes and ketones to α,β-unsaturated aldehydes

Phosphonate reagents were developed for the two-carbon homologation of aldehydes or ketones to unbranched- or methyl-branched α,β-unsaturated aldehydes. The phosphonate reagents, diethyl methylformyl-2-phosphonate dimethylhydrazone and diethyl ethylformyl-2-phosphonate dimethylhydrazone, contained a protected aldehyde group instead of the usual ester group. A homologation cycle entailed condensation of the reagent with the starting aldehyde, followed by removal of the dimethylhydrazone protective group with a biphasic mixture of 1 M HCl and petroleum ether. This robust two-step process worked with a variety of aldehydes and ketones. Overall isolated yields of unsaturated aldehyde products ranged from 71% to 86% after the condensation and deprotection steps.     

Development of catalysts for the stereoselective hydrogenation of α,β-unsaturated ketones

Iridium phosphinitoxazoline complexes were found to be new efficient catalysts for the asymmetric hydrogenation of arylated α,β-unsaturated ketones. Linear as well as cyclic substrates are hydrogenated with similar success, giving selectivities of up to 99.7% ee.     

Chiral tertiary amine N-oxides in asymmetric epoxidation of α,β-unsaturated ketones

Chiral tertiary amine N-oxides have been shown to undergo stereoselective oxygen transfer reaction in the epoxidation of chalcone derivatives with modest to good enantioselectivity.     

Modular approach to saturated and α,β-unsaturated ketones

2-Fluoro-6-pyridinyloxy derivatives of 2-ethoxyvinyl carbinols react with radicals derived from xanthates by an addition-fragmentation pathway to give highly functionalized ketones after acid hydrolysis. 1,4-Diketones are readily accessible by this approach. α,β-Unsaturated ketones can be obtained by starting with geminal acetoxy xanthates prepared by addition of a simpler xanthate to vinyl acetate.