2294-72-6Relevant articles and documents
Catalytic reduction and intramolecular cyclization of haloalkynes in the presence of nickel(I) salen electrogenerated at carbon cathodes in dimethylformamide
Ischay, Michael A.,Mubarak, Muhammad S.,Peters, Dennis G.
, p. 623 - 628 (2007/10/03)
Pentylidenecyclopentane can be conveniently prepared in up to 86% yield via the catalytic reduction of 1-iodo- or 1-bromo-5-decyne by [[2,2′-[1,2- ethanediylbis(nitrilomethylidyne)]bis[phenolato]]-N,N′,O,O′] -nickelate(I) electrogenerated at a carbon cathode in dimethylformamide containing tetramethylamnionium tetrafluoroborate. This electrosynthesis can be accomplished at potentials for which the haloalkynes are electroinactive, and it can be completed within 30 min at room temperature. Attempts to synthesize pentylidenecyclobutane and pentylidenecyclohexane from 1-halo-4-nonynes and 11-halo-5-undecynes, respectively, under similar conditions afford the carbocycles in very low yields (2% and 6%, respectively), Other products derived from the various haloalkynes are dimers, alkynes, and 1-alkenynes. Dimers (alkadiynes) arising From 1-halo-4-nonynes and 11-halo-5-undecynes are formed in yields ranging from 80% to 89%, whereas icosa-5, 15-diyne (the dimer obtained from a 1-halo-5-decyne) is found in significantly lower yield (≤ 13%). Alkynes and 1-alkenynes are produced in yields of 3-10% and 2-3%, respectively. A mechanistic scheme, involving alkyn-1-yl radicals arising from niekel(I) salon catalyzed cleavage of the carbon-halogen bond of each haloalkyne, is proposed to account for the formation of all products.
Cyclizations during the Grignard Reactions of ω-Bromoalkynes
Crandall, Jack K.,Michaely, William J.,Collonges, Francois,Nelson, Deanna J.,Ayers, Timothy A.,Gajewski, Joseph J.
, p. 1473 - 1490 (2007/10/03)
The Grignard reactions of a number of ω-bromoalkynes have been shown to undergo regioselective cyclizations in certain instances to give the smaller possible carbocycle. These cyclizations are shown to result from two competing processes, whose relative efficiencies depend upon the chain length and the remote substitutent on the acetylene. These are interpreted as a radical cyclization which occurs only during the time the Grignard is being formed from the bromide and an organometallic reaction which slowly transforms the Grignard reagent into its cyclic isomer. The mechanistic details of these transformations are discussed.
REDUCTION DE DERIVES D'ALCOOLS PROPARGYLIQUES CATALYSEE PAR UN COMPLEXE DE PALLADIUM ZEROVALENT
Colas, Yann,Cazes, Bernard,Gore, Jacques
, p. 165 - 173 (2007/10/02)
Catalysis by tetrakis(triphenylphosphine)palladium of the reaction of hydride donnors with secondary propargylic bromides, mesylates and phosphates increases markedly the amount of allene produced.The best results in that direction are obtained with mesylates and phosphates by using lithium triethylborohydride.The reaction then occurs with an ANTI introduction of the hydride with respect to the leaving group.A mechanism is proposed which explains the influence of the various parameters of the reaction.
