- Hydrogen-free homogeneous catalytic reduction of olefins in aqueous solutions
-
(Chemical Equation Presented) Herein we report a study involving the homogeneous catalytic reduction of unsaturated substrates in aqueous solutions or water-organic solvent mixtures. The reduction of olefins has been carried out in the presence of catalytic amounts of [Fe(CN)5NH3] 3- and excess of NH2OH, which under mild reaction conditions can be used to reduce carbon-carbon unsaturations without affecting carbonyl functionalities and aromatic rings. To explore the scope of the catalytic reduction, a wide variety of representative unsaturated substrates have been examined. The steric effects of the substituents on the carbon-carbon multiple bond as well as the regioselectivity and stereoselectivity of the catalyst have been studied. The deuterium kinetic isotope effect on the catalytic reduction of double bonds in olefins has been analyzed, and no significant kinetic isotope effect was found. Among the great advantages of this novel procedure for catalytic reduction are that hydrogen and high pressures are not needed, the catalyst is inexpensive and easily prepared, and water as well as water-organic solvent mixtures can be used as reaction media.
- Gaviglio, Carina,Doctorovich, Fabio
-
p. 5379 - 5384
(2008/12/20)
-
- Stereoselective homogeneous hydrogenation. The basis of preferential anti-isomer formation in acyclic systems
-
Directed homogeneous hydrogenation of olefins derived from methyl acrylate proceeds with high selectivity.The reactant must possess a polar substituent at a chiral centre situated in the α'-position; this may be -OH, CO2R or NHCOR.The catalyst should be a cationic chelating rhodium biphosphine complex.In all cases high anti-stereoselectivity is observed in the reduced product, and this can be rationalised by a simple and general model.With an optically active catalyst, efficient kinetic resolution occurs, providing a means of access to optically active acrylates.Experimental details of typical hydrogenation reactions are provided.
- Brown, John M.,Cutting, Ian,James, Alun P.
-
p. 211 - 217
(2007/10/02)
-
- STEREOSPECIFIC MICHAEL ADDITION OF DITHIOESTER ENETHIOLATES WITH ACYCLIC ENONES
-
Cis lithium enethiolates, generated from substituted dithioesters, undergo 1,4-addition with various β-monosubstituted α-unsaturated ketones.With acyclic enones one of the two resulting diastereomeric 5-oxodithioesters is predominantly formed (ratio up to 95 : 5).Its anti configuration was proven by chemical correlation in one case.Evidence for the stereospecificity of this Michael addition is given.
- Kpegba, Kafui,Metzner, Patrick,Rakotonirina, Rose
-
p. 1505 - 1508
(2007/10/02)
-
- ERYTHRO SELECTIVE CROSS ALDOL REACTION VIA α-SILYL TRIMETHYLSILYL ESTERS.
-
Various fluoride ion mediated reactions of aliphatic α-silyl trimethylsilyl esters 1 with benzaldehyde have been investigated.Moderate erythro stereoselectivity is observed.
- Bellassoued, Moncef,Dubois, Jacques-Emile,Bertounesque, Emmanuel
-
p. 2623 - 2626
(2007/10/02)
-
- HIGHLY DIASTEREOSELECTIVE TANDEM ALKYLATION OF ACYCLIC α,β-UNSATURATED ESTERS BASED ON THE NOVEL USE OF DITHIOACETAL UNIT
-
Highly diastereoselective tandem alkylation process of acyclic α,β-unsaturated esters was developed based on the novel use of dithioacetal as a stereocontrolling unit.
- Kawasaki, Hisashi,Tomioka, Kiyoshi,Koga, Kenji
-
p. 3031 - 3034
(2007/10/02)
-
- REVERSIBLE COUPLING OF A SUBSTITUTED ALLYLIC RADICAL WITH MOLECULAR OXYGEN IN A TOCO REACTION OF 5-METHYLHEPTA-1,3,6-TRIENE
-
p-Toluenethiol/oxygen co-oxidation of 5-methylhepta-1,3,6-triene (1) gives inter alia only one (6a) of four possible diastereoisomeric dioxolanes, and threo- and erythro-isomers of the 1,4-addition product (10, 11).The variation in relative yields with thiol concentration indicates that coupling of the allylic radical (2) with oxygen is reversible.
- Barker, Philip J.,Beckwith, Athelstan L. J.,Fung, Y.
-
-
- OXIDATIVE COUPLING REACTIONS UNDER PTC CONDITIONS
-
Succinic acid derivatives have been prepared from cyanohalides under PTC conditions in good yields.
- Gogte, V.N.,Natu, A.A.,Pandit, V.S.
-
p. 4131 - 4134
(2007/10/02)
-
- DIMETALATED TERTIARY SUCCINAMIDES. ALKYLATION AND ANNELATION REACTIONS
-
The reactions of dimetalated succinamides 1 with a variety of electrophiles give 2,3-disubstituted adducts (2) with high diasterioselectivity and annelated products (6-9).
- Mahalanabis, K.K.,Mumtaz, M.,Snieckus, V.
-
p. 3971 - 3974
(2007/10/02)
-