Dicarboxylic acids are compounds of high value, but to date long-chain α,ω-dicarboxylicacids have been difficult to access in a direct way. Unsaturatedfattyacids are ideal starting materials with their molecular structure of long methylene sequences and a carboxylate functionality, in addition to a double bond that offers itself for functionalization. Within this paper, we established a direct access
Characterization and Dynamics of [Pd(L−L)H(solv)]<sup>+</sup>, [Pd(L−L)(CH<sub>2</sub>CH<sub>3</sub>)]<sup>+</sup>, and [Pd(L−L)(C(O)Et)(THF)]<sup>+</sup> (L−L = 1,2-(CH<sub>2</sub>PBu<sup>t</sup><sub>2</sub>)<sub>2</sub>C<sub>6</sub>H<sub>4</sub>): Key Intermediates in the Catalytic Methoxycarbonylation of Ethene to Methylpropanoate
作者:William Clegg、Graham R. Eastham、Mark R. J. Elsegood、Brian T. Heaton、Jonathan A. Iggo、Robert P. Tooze、Robin Whyman、Stefano Zacchini
DOI:10.1021/om010938g
日期:2002.4.29
A detailed spectroscopic study has allowed the solution structure and dynamic properties of all the intermediates in the Pd-catalyzed methoxycarbonylation of ethene to be established. [Pd(L-L)H(solv)](-) 1 (L-L = 1,2-(CH2PBu2t)(2)C6H4; solv = MeOH, 1a; (PrOH)-O-n, 1b; THF, 1c; EtCN, 1d) is static, and the two inequivalent P atoms do not become equivalent through solvent exchange over all the temperatures studied. [Pd(L-L)(CH2CH3)](+), 2, contains a strong beta-agostic C-H interaction which is remarkably stable and is not displaced even in strongly coordinating solvents such as EtCN. C-alpha and C-beta Of the ethyl group in 2 become equivalent via a stereospecific interchange involving [Pd(L-L)H(eta(2)-C2H4)](+) without making the two P atoms equivalent; at higher temperatures these two inequivalent P atoms do become equivalent probably via a T-shaped intermediate. For [Pd(L-L)(C(O)Et)(solv)](+), 6, there is no beta-agostic C-H interaction and multiple C-13-labeling of the C(O)Et group shows that the inequivalent P atoms become equivalent via movement of the intact C(O)Et group. The crystal structure of the related complex [Pd(L-L)(C(O)Et)Cl] cocrystallized with dibenzylacetone has been determined.
A Comprehensive Mechanistic Picture of the Isomerizing Alkoxycarbonylation of Plant Oils
olefin substrates, but virtually no effect of the doublebond position within the substrate. Compared to higher olefins, ethylene carbonylation under identical conditions is much faster, likely due not just to the occurrence of reactive linear acyls exclusively but also to an intrinsically favorable insertion reactivity of the olefin. The alcoholysis reaction is slowed down for higher alcohols, evidenced