(S)-5-Methyl-tetrahydropyran-2-one 1 is a by-product in the production of key intermediates of steroidal hormones. Asymmetric synthesis of natural oxacyclododecindione-type macrolactones 2 and 3 has been realized for the first time from (S)-1 in seven and eight steps with 37% and 27% overall yield, respectively.

AbstractAddition of LiCl to Ti(O‐iPr)4 and (S)‐BINOL provides an efficient catalyst system which allows highly enantioselective coupling of various aldehydes with Chan′s diene (I).

Achiral additives can dramatically enhance the enantioselectivities in the BINOL–Ti(IV) complex catalyzed aldol condensations of aldehydes with Chan’s diene. The best results were obtained by using 2.0equiv of LiCl with respect to (S)-BINOL/Ti(Oi-Pr)4 as the additive. In the presence of 4.0mol% of LiCl and 2.0mol% of BINOL/Ti(Oi-Pr)4, all aldehydes tested gave δ-hydroxy-β-ketoesters as almost pure single enantiomers. Moreover, the present catalyst system was highly effective on reducing the catalyst loadings to 0.1mol%.

[reaction: see text] The poly(ethylene glycol)-supported ruthenium precatalyst shown above is highly effective for asymmetric transfer hydrogenation of unfunctionalized aromatic ketones by HCOONa in neat water, affording fast rates, good to excellent enantioselectivities, and outstanding reusability.

A new supported chiral diamine has been developed and shown to be highly effective in ruthenium-catalysed asymmetric transfer hydrogenation of simple aromatic ketones. (C) 2003 Elsevier Ltd. All rights reserved.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A fluorous polymeric phosphine, when combined with supercritical CO2 (scCO2) and rhodium, effects fast and highly chemoselective hydroformylation of acrylates, one of the least reactive olefins in hydroformylation reactions.

Palladium-catalyzed olefination of aryl halides led to a variety of fluorous ponytail-substituted, functionalized aryl compounds with good to excellent yields. The same chemistry was also applied to the synthesis of binaphathols bearing fluorinated ponytails.

Fluoroalkyl-derivatised R-BINAP ligands have been prepared, characterised and applied in the ruthenium-catalysed asymmetric hydrogenation of dimethyl itaconate.

A new method is presented with which achiral, conformationally flexible biphenylphosphites can be activated by easily available chiral alcohols to give monodentate phosphite ligands that are effective in rhodium-catalysed enantioselective hydrogenation.

A series of phosphine oxides has been synthesised by the palladium-catalysed Suzuki coupling of arylboronic acids with OPPh2(o-C6H4Br). On reduction with trichlorosilane, functionalised, biphenyl-based phosphine ligands were obtained in good yields. Our preliminary results indicate these ligands to be effective for palladium-catalysed C–C coupling reactions including the formation of their own oxides.

Palladium-catalyzed allylic alkylation with a variety of active methylene compounds has been carried out in the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]). Phosphine ligands are found to exert a profound effect on the active palladium species, with the more electron-donating ones such as PCy3 affording faster rates and the strong electron acceptors such as P(OPh)3 affording extremely low conversions. In the most commonly used molecular solvent, THF, the reaction is slower and the choice of ligands is more limited. These observations may be accounted for by the allylpalladium intermediate existing in different forms in the two solvents.

Diastereomerically pure menthyl binaphthylphosphite ligands, easily accessible from the inexpensive, racemic binaphthol, l-menthol and PCl3, are shown to be effective in the rhodium-catalysed enantioselective hydrogenation of prochiral olefins.

[figure: see text] Palladium-catalyzed arylation of the electron-rich olefin butyl vinyl ether has been accomplished in the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), using as the arylating agents aryl iodides and bromides instead of the commonly used, but commercially unavailable and expensive, aryl triflates. The reaction proceeds with high efficiency and remarkable regioselectivity, leading almost exclusively to substitution by various aryl groups at the olefinic carbon alpha to the heteroatom of butyl vinyl ether.

This study attempts to answer if inexpensive, easily available carbonylated phosphines could be used as CO2-philic ligands to replace the expensive, fluoroalkylated phosphines for catalysis in supercritical CO2 (scCO2). Toward this end, a series of alkoxycarbonylated arylphosphines were examined in the rhodium-catalyzed hydroformylation in scCO2. The reaction rate was found to vary with the number of the carbonyl groups incorporated into the phosphines and with the nature of the olefins.

A novel, high-yield route has been developed for the synthesis of perfluoroalkylated arylphosphines, involving simple, copper-mediated coupling of haloarylphosphine oxides with perfluoroalkyl iodides followed by reduction with trichlorosilane.

A series of ponytail-appended arylphosphines P(C6H4R-m)(3) (m=4, R=n-C6F13 1, n-CH2CH2C6F13 3, n-C6H13 4, n-C10H21 5 or n-C16H33 6; m=3, R=n-C6F13 2) have been studied in the rhodium-catalysed hydroformylation of higher olefins in supercritical CO2 (scCO(2)), with the perfluoroalkylated ligands exhibiting the highest and the alkylated one the lowest activities. The high rates derived from 1 and 2 probably originate from the strong electron-withdrawing effect of their ponytails, while the slow rates observed with 4-6 are mainly due to the low solubility of these ligands in scCO(2).

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.