Abstract:
The borane reduction of prochiral ketones to optically pure alcohols is effectively achieved by the utilization of catalytic amounts of the new and valuable oxazaborolidine catalysts of formula (I). ##STR1##
Abstract:
A hydrogenation process is described for the production of a hydroxylic compound selected from alcohols and diols by hydrogenation of a corresponding unsaturated organic compound selected from esters, diesters and lactones which involves use of two hydrogenation zones (11, 36), each containing a charge of a hydrogenation catalyst (12, 37). In a first phase of operation one of the hydrogenation zones (36 or 11) is in standby condition and a stream of hot hydrogen-containing gas is passed therethrough. Meanwhile a vaporous feed stream comprising a hydrogen-containing gas and the unsaturated organic compound to be hydrogenated, e.g. dimethyl 1,4-cyclohexanedicarboxylate, is fed to the active zone (11 or 36). This feed stream can include the gas stream from the first mentioned hydrogenation zone (36 or 11). In a second phase of operation the roles of the reactors (11, 36) are switched so that the zone (36 or 11) previously in reactivation condition becomes the active zone whilst the zone that was formerly active (11 or 36) goes into reactivation condition and its partially deactivated catalyst charge is reactivated by the hot hydrogen-containing gas stream.
Abstract:
This invention relates to asymmetric syntheses in which a prochiral or chiral compound is contacted in the presence of an optically active metal-ligand complex catalyst to produce an optically active product.
Abstract:
A process is provided whereby organic carbonyl substrates, including esters, ketones and amides, are reduced in a reaction with a silane reducing reagent and a catalyst. Effective catalysts broadly include those which consist of a group 4, 5 or 6 metal which either: a) is in less than its maximum oxidation state or is capable of being converted to a complex in less than its maximum oxidation state; and/or is a group 4, 5 or 6 metal hydride. Exemplary catalysts include titanium-containing catalysts such as (bis trimethylphosphine) titanocene, trimethyl phosphine adduct of a (hydrido) silyl complex of titanocene, titanocene dichloride and titanocene monochloride.
Abstract:
In a method of carrying out organic conversions via heterogeneous phase transfer catalysis by contacting immiscible liquid phases containing respective substances capable of interacting, with a solid catalyst to promote the transfer of reactive species from one liquid phase to another, the improvement comprises employing as catalyst a cation exchanged form of a 2:1 layered silicate clay with layer charge densities in the range of above 0.4 to 2.0 containing an onium ion containing one or more alkyl hydrocarbon chains and maintaining the materials in emulsified form by having a sufficient chain length of an alkyl group relative to the charge density of the clay.
Abstract:
2-Methyl-3-(3-methylphenyl)-propan-1-ol, 2-methyl-3-(3,5-dimethylphenyl)-propan-1-ol, 1-(3-methylphenyl)-2-methylbutan-3-ol and 1-(3,5-dimethylphenyl)-2-methylbutan-3-ol, their preparation and use as fragrances.
Abstract:
Optically active compounds of the formula I ##STR1## in which R.sup.1 is C.sub.1 -C.sub.4 -alkyl, phenyl or benzyl, R.sup.2 is a radical of the formula II or IIa ##STR2## in which R.sup.3 is H or --CH.sub.3, or R.sup.1 and R.sup.2 together form a radical of the formula ##STR3## in which R.sup.2 has the meaning given above; and * represents predominantly R or predominantly S configuration.The compounds can be polymerized to give homopolymers or copolymers. The compounds and the polymers can be complexed with iridium(I) salts in the presence of a diene. The complexes are suitable as enantioselective catalysts.
Abstract:
A process is described for the improved synthesis of the optically pure C.sub.10 -C.sub.18 fragment of the macrolide structure of the immunosuppressant FK-506. This compound is also useful as an intermediate for preparing FK-506 derivatives.
Abstract:
A process for reducing an aldehyde or ketone in the presence of a stable, highly active catalyst which is insoluble in a solvent and which can be recovered easily from the reaction system after completion of the reaction and used repeatedly, characterized in that an aldehyde or ketone having a carbonyl group is reacted with an alcohol in the presence of hydrous zirconium oxide as the catalyst.
Abstract:
Optically active compounds of the formula I ##STR1## in which R.sup.1 is C.sub.1 -C.sub.4 -alkyl, phenyl or benzyl, R.sup.2 is a radical of the formula II or IIa ##STR2## in which R.sup.3 is H or --CH.sub.3, or R.sup.1 and R.sup.2 together form a radical of the formula ##STR3## in which R.sup.2 has the meaning given above; and * represents predominantly R or predominantly S configuration.The compounds can be polymerized to give homopolymers or copolymers. The compounds and the polymers can be complexed with iridium(I) salts in the presence of a diene. The complexes are suitable as enantioselective catalysts.