Catalyst-free conjugated addition of thiols to alpha,beta-unsaturated carbonyl compounds in water

[reaction: see text] Catalyst-free conjugate addition of thiols to alpha,beta-unsaturated carbonyl compounds in water is reported. beta-Sulfido carbonyl compounds were formed at room temperature, in short times and with excellent chemoselectivity. Competitive dithiane/dithiolane formation, transesterification, and ester cleavage were not observed. Water played a dual role in simultaneously activating the alpha,beta-unsaturated carbonyl compound and the thiol. This new methodology constitutes an easy, highly efficient, and green synthesis of beta-sulfido carbonyl compounds.     

Amine-catalyzed addition of azide ion to alpha,beta-unsaturated carbonyl compounds

[formula: see text] A new protocol for the beta-azidation of alpha,beta-unsaturated carbonyl compounds is described. The method employs tertiary amines as catalysts for azide addition. The azide source is a 1:1 mixture of TMSN3 and AcOH. Tertiary amines, either in solution or bound to a solid support, are efficient catalysts for the reaction.     

Michael addition of selenoamides to alpha,beta-unsaturated carbonyl compounds: stereocontrolled synthesis of delta-oxo selenoamides and their reactivity

[reaction: see text] Lithium eneselenolates generated from selenoamides underwent Michael addition to alpha,beta-unsaturated esters and ketones with high diastereoselectivity to give delta-oxo selenoamides in moderate to high yields within a few seconds. Further selective transformations of the delta-oxo selenoamides were also achieved.     

Organocatalytic and direct asymmetric vinylogous Michael addition of alpha,alpha-dicyanoolefins to alpha,beta-unsaturated aldehydes

The first highly regio-, chemo-, diastereo- and enantioselective direct vinylogous Michael addition of alpha,alpha-dicyanoolefins to alpha,beta-unsaturated aldehydes is described, employing readily available chiral alpha,alpha-diarylprolinol salts as iminium organocatalysts.     

Palladium-catalyzed conjugate addition of organosiloxanes to alpha,beta-unsaturated carbonyl compounds and nitroalkenes

The addition of aryltrialkoxysilanes to alpha,beta-unsaturated carbonyl compounds (ketones, aldehydes) and nitroalkenes in the presence of SbCl(3), TBAF, AcOH, and a catalytic amount of Pd(OAc)(2), in CH(3)CN at 60 degrees C, provides the corresponding conjugate addition products in moderate to good yields. The addition of equimolar amounts of SbCl(3) and TBAF is necessary for this reaction to proceed smoothly. The arylpalladium complex, which is generated by the transmetalation from a putative hypercoordinate silicon compound, is considered to be the catalytically active species.     

An efficient enantioselective method for asymmetric Michael addition of nitroalkanes to alpha,beta-unsaturated aldehydes

The addition of nitroalkanes to alpha,beta-unsaturated aldehydes under the catalysis of (S)-2-(diphenyl(trimethylsilyloxy)methyl)pyrrolidine and lithium acetate as additive afforded gamma-nitroaldehydes in good yield and up to 97% ee.     

Highly enantioselective Michael addition of malononitrile to alpha,beta-unsaturated ketones

The highly enantioselective Michael addition of malononitrile to acyclic and cyclic alpha,beta-unsaturated ketones has been developed. The Michael reaction catalyzed by a primary amine derived from quinidine proceeded smoothly and provided the desired adducts with excellent enantioselectivities (83-97% ee).     

Conjugate addition of organosiloxanes to alpha,beta-unsaturated carbonyl compounds catalyzed by a cationic rhodium complex

[reaction: see text] A novel, additive-free, and clean conjugate addition reaction of organosiloxanes to alpha,beta-unsaturated carbonyl compounds catalyzed by a cationic rhodium complex in water-containing solvent has been developed. A plausible reaction mechanism involving the additive-free transmetalation step between the rhodium complex and the silicon reagent is proposed.     

Synthetic applications of beta-fluoroalkylated alpha,beta-unsaturated carbonyl compounds

Beta-fluoroalkylated alpha,beta-unsaturated carbonyl compounds constitute efficient building blocks for the synthesis of complex fluorinated compounds. As the fluorinated moiety generally increases their reactivity, it also brings important modifications which can change the chemical behavior and selectivity. Their use has been already largely demonstrated. Nevertheless, the synthetic potential has not yet been fully explored and, consequently should play an important role in the design of new sophisticated fluorinated molecules. Nevertheless, it shall be important to develop new synthetic methods to enlarge their availability and their diversity.     

Asymmetric multifunctional organocatalytic Michael addition of nitroalkanes to alpha,beta-unsaturated ketones

Cinchona alkaloid derived primary amine thioureas organocatalyzed Michael addition of nitroalkanes to enones in good yield and up to 98% ee and offered a new way to construct quaternary stereocenters from enones and nitroalkanes.     

Pd(II)-bipyridine catalyzed conjugate addition of arylboronic acid to alpha,beta-unsaturated carbonyl compounds

[Reaction: see text]. A Pd(II)-catalyzed conjugate addition of arylboronic acid to alpha,beta-unsaturated ketones, aldehydes, esters, etc. in the presence of 2,2'-bipyridine was developed. A mechanism involving transmetalation, insertion of the carbon-carbon double bond into the C-Pd bond, and protonolysis of the resulting C-Pd bond is proposed. The reaction conditions are mild and the yield is high. The presence of 2,2'-bipyridine is crucial for the reaction to inhibit beta-hydride elimination.     

Michael addition of ortho-lithiated aryloxiranes to alpha,beta-unsaturated malonates: synthesis of tetrahydroindenofuranones

A short and efficient synthesis of tetrahydroindenofuranones based on the Michael addition of ortho-lithiated aryloxiranes to alkylidene malonates followed by the nucleophilic oxirane ring-opening and subsequent lactonization is described. The methodology has been applied to the synthesis of a structural analogue of epipodophyllotoxins.     

Catalytic asymmetric conjugate addition of grignard reagents to alpha,beta-unsaturated sulfones

A highly efficient method is reported for the asymmetric conjugate addition of Grignard reagents to alpha,beta-unsaturated 2-pyridylsulfones. Using a Cu/TolBinap complex, excellent enantioselectivities and high yields are obtained for a wide variety of aliphatic substrates.     

Rhodium-catalysed 1,4-addition of diarylindium hydroxides to alpha,beta-unsaturated carbonyl compounds

Diarylindium(III) hydroxides react with alpha,beta-unsaturated carbonyl compounds in the presence of a rhodium catalyst to afford the 1,4-addition products in high yield. This reaction demonstrates the utility of diarylindium(III) hydroxide as an aryl source with rhodium catalysts.     

Thiourea-catalyzed asymmetric michael addition of activated methylene compounds to alpha,beta-unsaturated imides: dual activation of imide by intra- and intermolecular hydrogen bonding

A thiourea-catalyzed asymmetric Michael addition of activated methylene compounds to alpha,beta-unsaturated imides derived from 2-pyrrolidinone and 2-methoxybenzamide has been developed. In the case of 2-pyrrolidinone derivatives, the reaction with malononitrile proceeded in toluene with high enantioselectivity, providing the Michael adducts in good yields. However, the nucleophiles that could be used for this reaction were limited to malononitrile due to poor reactivity of the substrate. Further examination revealed that N-alkenoyl-2-methoxybenzamide was the best substrate among the corresponding benzamide derivatives bearing different substituents on the aromatic ring. Indeed, several activated methylene compounds such as malononitrile, methyl alpha-cyanoacetate, and nitromethane could be employed as a nucleophile to give the Michael adducts in good to excellent yields with up to 93% ee. The results of spectroscopic experiments clarified that this enhanced reactivity can be attributed to the intramolecular hydrogen-bonding interaction between the N-H of the imide and the methoxy group of the benzamide moiety. Thus, the key to the success of the catalytic enantioselective Michael addition is dual activation of the substrate by both intramolecular hydrogen bonding in the imide and intermolecular hydrogen bonding with thiourea 1a, as well as the activation of a nucleophile by the tertiary amine of the bifunctional thiourea.     

Oxidation of allylic alcohols to alpha,beta-unsaturated carbonyl compounds with aqueous hydrogen peroxide under organic solvent-free conditions

Allylic alcohols are chemoselectively oxidized to alpha,beta-unsaturated carbonyl compounds in high yield with aqueous H(2)O(2) in the presence of Pt black catalyst under organic solvent-free conditions. The catalyst is easily recyclable and effective for at least 7 cycles.     

Unprecedented copper-catalyzed asymmetric conjugate addition of organometallic reagents to alpha,beta-unsaturated lactams

For the first time, an excellent enantioselectivity has been obtained in the conjugate addition of hard organometallic reagents to alpha,beta-unsaturated lactams bearing appropriate protecting-activating groups on the nitrogen.