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. Supporting Information Available. Detailed experimental procedures, and compound characterization data. This material is available free of charge via the Internet at http://pubs.acs.org.

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.

a b s t r a c tAlkynes react with organoborons under a CO atmosphere in the presence of a rhodium(I) catalyst to afford mainly 5-aryl-2(5H)-furanones, a,b-unsaturated ketones, and indanones. The product selectivity can be tuned by modifying the reaction conditions.

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.

A palladium-catalysed reaction of conjugated enyne oxiranes with organoboron reagents is described. This method allows aryl-substituted vinylallenes containing a hydroxyl group on the allylic position to be synthesized, with good diastereomeric ratios, under mild conditions.

Acetate derivatives of 2-en-4-yne alcohols 1 and enyne oxiranes 4 regioselectively underwent 1,5-substitution (S N 2'')r eactions with Grignard reagents in the presence of an iron compound to provide vinylallenes exclusively with the (E)-configuration. An alkali salt was needed to avoid the hydride-promoted reductive1 ,5-substitutionp athway for 1, whereas no such additive was neededf or the effective conversion of 4 into the desired alkylated or arylated vinylallene structure.Scheme1.1,5-Substitution reaction of 1-(1-chloroethyl)-2-ethynylcyclohex-1ene with Grignard reagents (HMPA = hexamethylphosphoramide).Scheme2.1,5-Substitution of 2-en-4-ynea cetates with lithium organocuprates.

Palladium-catalysed reactions of γ,δ-Epoxy-α,β-Unsaturated esters and amides with NaBAr4 reagents proceeded regio- and stereo-selectively, producing allylic homoallyl alcohols with aryl-substituents in the allylic position for a wide range of substrates....

Palladium-Catalyzed Alkoxycarbonylation of (Z)-2-En-4-yn Carbonates Leading to 2,3,5-Trienoates. -The reaction (E)-configurated substrates carbonate generates only a small amount of the desired vinylallene together with a complex mixture of by-products. -(AKPINAR, G. E.; KUS, M.; UCUENCUE, M.; KARAKUS, E.; ARTOK*, L.; Org. Lett. 13 (2011) 4, 748-751, http://dx.