Palladium-catalysed regio- and stereoselective arylative substitution of γ,δ-epoxy-α,ß-unsaturated esters and amides by sodium tetraaryl borates.

Palladium-catalysed reactions of γ,δ-epoxy-α,ß-unsaturated esters and amides with NaBAr4 reagents proceeded regio- and stereoselectively, producing allylic homoallyl alcohols with aryl-substituents in the allylic position for a wide range of substrates. AsPh3 was found to be a competent ligand for the arylation reaction, whereas phosphine ligand/Lewis acidic organoboron combinations favoured the substitution reaction by oxygen nucleophiles (e.g. H2O, ROH).

Palladium-Catalyzed Alkoxycarbonylation of Conjugated Enyne Oxiranes: A Diastereoselective Method for the Synthesis of 7-Hydroxy-2,3,5-trienoates.

Palladium-catalyzed alkoxycarbonylative 1,5-substitution of conjugated enyne oxiranes provides a diastereoselective route to (E)-configured 7-hydroxy-2,3,5-trienoates. The reactions proceeded in a highly stereoselective manner, possibly through sequential formation of π-allylpalladium and σ-vinylallenyl palladium complexes. The major diastereomeric form of the product is determined by the configuration of the alkenyl moiety of the substrate.

Regio- and stereoselective synthesis of 2,3,5-trienoates by palladium-catalyzed alkoxycarbonylation of conjugated enyne carbonates.

Palladium-catalyzed carbonylation of 2,4-enyne carbonates in an alcohol and under balloon pressure of CO proceeds through 1,5-substitution to yield (E)-2,3,5-trienoates. The olefin geometry of the substrate is important to control the overall stereochemistry of this alkoxycarbonylation method. The reaction proceeds through successive formation of π-allylpalladium with an R(3) group oriented syn and σ-allenyl palladium complexes.

Rhodium- and palladium-catalyzed 1,5-substitution reactions of 2-en-4-yne acetates and carbonates with organoboronic acids.

Two methods involving the rhodium-catalyzed reaction of 2-en-4-yne acetates and the palladium-catalyzed reaction of 2-en-4-yne carbonates with organoboronic acids were investigated; both afforded exclusively the (E)-configured vinylallenes. The coordinative interaction of the rhodium with the acetate group promoted the δ-elimination of Rh(I)-OAc from the alkenylrhodium intermediate II in both syn and anti modes, with the syn-elimination being the major path. DFT calculations revealed that a conformer of this intermediate (II), which can lead to the (E)-configured vinylallene product via the syn-elimination mode, is energetically the most favorable conformer. The rhodium-catalyzed procedure is not applicable to reactions involving (E)-configured enyne acetates, because the geometry of the alkenylrhodium intermediate that is derived from the corresponding (E)-enyne acetate would not allow such coordinative interaction to occur. The palladium-catalyzed method, which proceeds through formation of the σ-vinylallenylpalladium intermediate, B, is suitable for both the (E)- and (Z)-configured enyne carbonates and appears to have a wider scope for both organoboronic acids and enyne substrates. The palladium-catalyzed reaction of an enantiomerically enriched enyne carbonate proceeded with racemization.

Palladium-catalyzed alkoxycarbonylation of (Z)-2-en-4-yn carbonates leading to 2,3,5-trienoates.

Pd(0)-catalyzed carbonylation of (Z)-2-en-4-yn carbonates in the presence of a balloon pressure of CO in an alcohol donates vinylallenyl esters with an exclusively E-configuration and in high yields. The fact that no such reactivity could be observed with E-configured enyne carbonates may indicate that the reaction is promoted via the cooperative coordination of palladium with both alkynyl and carbonate moieties.

Rhodium catalysed chemo- and stereoselective arylative and alkenylative cyclisation reactions of unsymmetric diynes containing a terminal alkyne moiety with organoboronic acids.

Unsymmetric diynes possessing a terminal alkyne moiety reacted with organoboronic acids both chemo- and stereoselectively to afford arylated or alkenylated exocyclic dienes by catalysis from the [Rh(cod)OCH(3)](2) complex. The use of a polar protic solvent, e.g. CH(3)OH is required for the success of the process under mild conditions.

Rhodium-catalyzed carbonylative arylation of alkynes with arylboronic acids: an efficient and straightforward method in the synthesis of 5-aryl-2(5H)-furanones.

5-Aryl-2(5H)-furanones can be synthesized by the Rh-catalyzed reactions of arylboronic acids with internal alkynes under a CO atmosphere.

Influence of menthol on caffeine disposition and pharmacodynamics in healthy female volunteers.

OBJECTIVES: The present study was undertaken to determine whether a single oral dose of menthol affects the metabolism of caffeine, a cytochrome P(450) 1A2 (CYP1A2) substrate, and pharmacological responses to caffeine in people. METHODS: Eleven healthy female subjects participated in a randomized, double-blind, two-way crossover study, comparing the kinetics and effects of a single oral dose of caffeine (200 mg) in coffee taken together with a single oral dose of menthol (100 mg) or placebo capsules. Serum caffeine concentrations and cardiovascular and subjective parameters were measured throughout the study. RESULTS: Co-administration of menthol resulted in an increase of caffeine t(max) values from 43.6+/-20.6 min (mean+/-SD) to 76.4+/-28.0 min ( P<0.05). The C(max) values of caffeine were lower in the menthol phase than in the placebo phase, but this effect was not statistically significant ( P=0.06). (AUC)(0-24), (AUC)(0- infinity ), terminal half-life and oral clearance were not affected by menthol. Only nine subjects' cardiovascular data were included in the analysis because of technical problems during the measurements. After caffeine, heart rate decreased in both treatment phases. The maximum decrease in heart rate was less in the menthol phase (-8.9+/-3.9 beats/min) than in the placebo phase (-13.1+/-2.1 beats/min) ( P=0.024). There were no statistically significant differences in systolic and diastolic blood pressures between the two treatments. CONCLUSIONS: We conclude that a single oral dose of pure menthol (100 mg) delays caffeine absorption and blunts the heart-rate slowing effect of caffeine, but does not affect caffeine metabolism. The possibility that menthol slows the absorption of other drugs should be considered.