Dimerization of alpha,beta-unsubstituted 1-alkenes, having at least three carbon atoms, in the presence of a catalyst comprising (a) a titanium-containing component of the formula Cp.sub.2 TiXY, wherein Cp represents an optionally alkyl-substituted cyclopentadienyl group, X represents a halogen atom or an alkyl group, and Y represents a halogen atom, (b) an alkylaluminum halide, and (c) a nitrogen Lewis base, is characterized by high reaction selectivity to certain dimer products and little formation of higher polymers.
Synthesis of methyl β-alkylcarboxylates by Pd/diphosphine-catalyzed methoxycarbonylation of methylenealkanes RCH2CH2C(R)=CH2
作者:Ilya E. Nifant’ev、Nadezhda T. Sevostyanova、Sergey A. Batashev、Alexey A. Vinogradov、Alexander A. Vinogradov、Andrei V. Churakov、Pavel V. Ivchenko
DOI:10.1016/j.apcata.2019.05.030
日期:2019.7
A series of methylenealkanes RCH2CH2(R)C = CH2 (R = n-butyl, n-hexyl, isopropyl and isobutyl), which are products of selective zirconocene-catalyzed dimerization of alpha-olefins, were introduced into Pd-catalyzed methoxycarbonylation. With the use of 5-methyleneundecane (1-hexene dimer) as a substrate, the roles of protic acid, Lewis acid and molecular hydrogen were established for model Pd(ll)/PPh3 and Pd(II)/diphosphine catalysts.A series of bridged diphosphines were studied as catalyst components L in PdCl2/L-catalyzed methoxycarbonylation in the presence of H-2. One of the nine diphosphines studied, trans-2,3-bis(diphenylphosphinomethyl)norbomane, demonstrated the best catalytic results in terms of catalytic activity, selectivity and isolated yields of the products. Under the optimized conditions during 24 h experiments, dimers RCH2CH2(R)C = CH2 were transformed to methyl carboxylates RCH2CH2(R)CHCH2COOMe with 99 +% regioselectivity; isolated yields were 62-81%.In that way, the catalytic methoxycarbonylation of synthetically available methylenealkanes is an effective approach to branched carboxylic acids, with high prospects for practical application.
Metallacyclopentane to metallacyclobutane ring contraction
作者:Stephan J. McLain、Jose Sancho、Richard R. Schrock
DOI:10.1021/ja00512a074
日期:1979.8
Selective dimerization of monosubstituted .alpha.-olefins by tantalacyclopentane catalysts
作者:S. J. McLain、J. Sancho、R. R. Schrock
DOI:10.1021/ja00537a035
日期:1980.8
Branched alkylphosphinic and disubstituted phosphinic and phosphonic acids: effective synthesis based on α-olefin dimers and applications in lanthanide extraction and separation
作者:I. E. Nifant'ev、M. E. Minyaev、A. N. Tavtorkin、A. A. Vinogradov、P. V. Ivchenko
DOI:10.1039/c7ra03770h
日期:——
been found that phosphinicacids 8–12 surpass di(2-ethylhexyl)phosphoric acid (extractant P204) in non-selective Ln3+ extractability (Ln = La, Pr, Nd, Dy and Lu). Significantly higher selectivity for heavy lanthanide extraction (Ln = Dy, Lu), compared to that of P204, is achieved by using a minimal excess of disubstituted phosphinicacids 13–24. Acid 13, which contains two branched substituents, demonstrated