Highly Selective Dimerization of Styrenes and Linear Co‐dimerization of Styrenes with Ethylene Catalyzed by a Ruthenium Complex

Abstract

Kopf gewinnt: Eine ungewöhnliche Kopf‐Kopf‐Dimerisierung von Styrolen gelingt mit dem nullwertigen Rutheniumkatalysator [Ru(η6‐cot)(η2‐dmfm)2] (cot=1,3,5‐Cyclooctatrien, dmfm=Dimethylfumarat) in Gegenwart primärer Alkohole; dabei entsteht das Homodimer mit hoher Regio‐ und Stereoselektivität. Das Katalysatorsystem eignet sich auch für die selektive Codimerisierung von Styrolen mit Ethen in hoher Ausbeute.

Heterodimerization of Olefins: A Highly Promising Strategy for the Selective Synthesis of Functionalized Alkenes

“…Although there is room for improvements in terms of yield and substrate spectrum, the reaction described could be groundbreaking for the development of new, atom‐economic pathways to other functionalized alkenes such as enol esters, vinyl ethers, or α,β‐unsaturated carbonyl compounds. Initial follow‐up work appears to confirm this assessment 23…”

In(OTf)3‐Catalyzed Highly Chemo‐ and Regioselective Head‐to‐Tail Heterodimerization of Vinylarenes with 1,1‐Diarylethenes

“…Selective formation of dimers 3 through tail‐to‐tail homodimerization has also been reported4 and the N‐heterocyclic carbene (NHC) nickel(II) hydride complex [(IPr)NiH]OTf (IPr=1,3‐bis(2,6‐diisopropylphenyl)imidazole‐2‐ylidene) promotes both homo‐ and heterodimerization of 1 in high chemo‐ and regioselectivity 4d. A ruthenium(0) complex, [Ru(η 6 ‐cot)(η 2 ‐dmfm) 2 ] (cot=1,3,5‐cyclooctatriene, dmfm=dimethyl fumarate), has been found to be efficient for the formation of alkenes 4 at 80–100 °C in alcoholic solvents in 53–66 % isolated yields 5. Moreover, a rhodium(I) complex, [RhCl(cod)] 2 (cod=1,5‐cyclooctadiene), in combination with t BuOH and Na 2 CO 3 at 160 °C facilitates the formation of trans ‐stilbenes 6 (24–63 % yields) from vinylarenes 1 through cleavage of the ortho CH bond 8…”

“…[1] Homodimerization may be considered simpler than heterodimerization between two different partners and yet a mixture of homodimers is often generated due to versatile dimerization modes. [1,2] As illustrated in Scheme 1, catalytic homodimerization of vinylarenes 1, such as styrene (Ar = Ph), gives the alkenes 2-4 through head-to-tail (h-t), [3] tail-to-tail (t-t), [4] and head-to-head (h-h) [5] homodimerization, respectively. Moreover, compounds 1 undergo cyclodimerization to produce the indan derivatives 5.…”

“…[4d] A ruthenium(0) complex, [RuA C H T U N G T R E N N U N G (h 6 -cot)A C H T U N G T R E N N U N G (h 2dmfm) 2 ] (cot = 1,3,5-cyclooctatriene, dmfm = dimethyl fumarate), has been found to be efficient for the formation of alkenes 4 at 80-100 8C in alcoholic solvents in 53-66 % isolated yields. [5] Moreover, a rhodium(I) complex, [RhClA C H T U N G T R E N N U N G (cod)] 2 (cod = 1,5-cyclooctadiene), in combination with tBuOH and Na 2 CO 3 at 160 8C facilitates the formation of trans-stilbenes 6 (24-63 % yields) from vinylarenes 1 through cleavage of the ortho C À H bond. [8] To the best of our knowledge, 1,1-diarylethenes 8 (Scheme 2) usually give indan products similar to 5 through cyclodimerization in the presence of Lewis acids, such as Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201101190.…”

Heterodimerisierung von Olefinen: eine vielversprechende Strategie zur selektiven Synthese funktionalisierter Alkene

“…Obwohl die Ausbeuten und das Substratspektrum noch verbesserungswürdig sind, könnte die vorgestellte Reaktion wegweisend für die Entwicklung neuer atomökonomischer Zugangswege zu anderen funktionalisierten Alkenen wie Enolestern, Vinylethern oder α,β‐ungesättigten Carbonylverbindungen sein. Erste Folgearbeiten scheinen diese Einschätzung zu bestätigen 23…”