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

Abstract

Heads you win: An unusual head‐to‐head dimerization of styrenes has been developed using the zero‐valent ruthenium catalyst [Ru(η6‐cot)(η2‐dmfm)2] (cot=1,3,5‐cyclooctatriene, dmfm=dimethyl fumarate) in the presence of primary alcohols to give the homo‐dimer in high regio‐ and stereoselectivity. The catalyst system is also effective for the selective co‐dimerization of styrenes with ethylene to give the co‐dimer in high yield.

Oligomerization of Olefins

“…Ru(cod)(cot) is effective for codimerization of dihydrofuran and N-vinylacrylamide with acrylates (Scheme 5.17) [162]. Codimerization of ethylene with styrene catalyzed by Ru(cod)(cot) yields 1-phenyl-1-butene [163], which is in contrast to that 3-phenyl-1-butene is obtained in the general hydrovinylation. …”

グリーン有機分子変換プロセスを指向したセリア担持ルテニウム触媒の開発

“…Remarkably, the regioselectivity of the reaction can be completely controlled by changing the solvent: the reaction in mesitylene selectively gave a linear dimer (15'). Note that, so far, only a zero-valent ruthenium complex 62) and an yttrium hydride complex 63) have been reported to catalyze the selective linear dimerization of styrenes, whereas many c a t a l y s t s h ave b e e n r e p o r t e d t o g ive b r a n c h e d dimers 64) 68) . The use of formalin instead of ethanol also promoted the reaction, and finally a mixture of ethanol and formalin was found to be the optimum additive.…”

“…Due to the similarity to the previous ruthenium complex-catalysis, in which the addition of a primary alcohol and the use of mesitylene as a solvent are essential 62) , the Ru/CeO2-catalyzed formation of linear dimers is considered to proceed via a ruthenacyclopentane intermediate (Scheme 3).…”

New Catalytic Performances of Ruthenium and Rhodium Complexes Directed toward Organic Synthesis with High Atom Efficiency

“…112,113 On the basis of our continuous study of the catalytic activity of a zero-valent ruthenium complex, [Ru(© 6 -cot)(© 2 -dmfm) 2 ], we found that it catalyzed an unusual head-to-head dimerization of styrenes 22 to (E)-1,4-diaryl-1-butenes 23 114,115 in the presence of primary alcohols (Scheme 20). 116 No significant effect was observed for the substituents on the phenyl ring in styrenes.…”

“…84,125 In sharp contrast, codimerization as well as co-oligomerization reactions of different alkenes are still quite difficult except for hydrovinylation of styrenes, 108113 and a challenging subject in modern organic and organometallic chemistry. 116 We report here zero-valent ruthenium-complex-catalyzed codimerization reaction of different alkenes; i.e., a codimerization reaction of N-vinylamides with alkenes as well as a cooligomerization reaction of N-vinylamides, acrylates, and ethylene, which offer novel and atom-economical methods for synthesis of enamides with high regio-and stereoselectivity in one step (Scheme 22). 126,127 N-Vinylamides with a large excess of alkenes under the same catalytic reaction conditions followed by hydrogenation gave 1:2 co-oligomers in up to 63% yield.…”