Recent Results in the Catalytic Oligomerization and Co‐oligomerization of Butadiene

Abstract

A number of new catalyst systems based on transition-metal compounds have been developed for the oligomerization and co-oligomerization of butadiene. These catalym promote dienylations and the formation of other C-C linkages, and make possible the synthesis of new open-chain and cyclic conipounds from butadiene.

Vicarious substitution of hydrogen with carbanions of dithioacetals

“…d Yield estimated from NMR spectra of crude reaction product. This compound was identified by comparison with an authentic sample.9 in view of a report that, in an n-BuLi/THF system, some dithioacetal carbanions react with nitroarenes mainly via an electron-transfer pathway, giving products of oxidative dimerization of the carbanions.6 We sought to perform VNS using diphenyl dithioacetals of formaldehyde (1) and benzaldehyde (2) since they are sufficiently acidic (1, pKa(Me2SO) = 30.8; 2, pK'a(Me2SO) = 23.0)7 to form carbanions in a t-BuOK/Me2SO system (f-BuOH pKa(Me2SO = 32.2),8 which was shown to be convenient for other VNS reaction. Reactions were carried out at room temperature for 30 min, with a great excess of base.…”

“…When this position is occupied, e.g., in p-nitrobiphenyl, the VNS does not proceed, possibly due to steric hindrance of the position ortho to the nitro group. For the same reason the carbanion from 2 does not react (1) Part 123 in the series Reactions of Organic Anions. Part 122: Mgkosza, M.; Kwast, A.; Joficzyk, A.; Stomka, E., submitted for publication in J. Org.…”

Metal catalysed hydrovinylation

“…This codimer is the result of the standard hydrovinylation of styrene followed by isomerisation to the internal olefin. At almost the same time, Mu ¨ller and coworkers 18 described the same reaction with Ni(acac) 2 -trialkylaluminiums-phosphites as catalytic systems. Although the selectivity to the hydrovinylated product was very poor, this report represents the start of Ni-catalysed hydrovinylation, a metal that is still the most important for this reaction.…”

Structure of the Complex Ni(C8H12)(L) and Its Reactivity toward Organometallic Reagents

“…Oxidative cyclizations of unsaturated hydrocarbons on Ni(0) are some of the most important elemental processes in organometallic chemistry both in the laboratory and in industry. − Among them, the oxidative cyclization of two molecules of 1,3-butadiene creates C8 chemicals, including cyclooctadiene, in industrial production. − In addition, not only Pd but also other transition metals such as Rh and Ru were found to promote similar oxidative dimerization and trimerization reactions. Since the pioneering work on mechanism and intermediates by Wilke and Brown in the 1970s, the behavior of the key intermediate, Ni II (C 8 H 12 )­(L), has been experimentally − and theoretically investigated, and several isomers 1a – e have been proposed (Scheme , upper right).…”