Alcohol cross-coupling reactions catalyzed by Ru and Ir terpyridine complexes

Abstract

Primary alcohols can be coupled with secondary benzylic alcohols by an air-stable catalytic system involving terpyridine ruthenium or iridium complexes.

C‐Alkylation of Ketones and Related Compounds by Alcohols: Transition‐Metal‐Catalyzed Dehydrogenation

“…[24] Crabtree et al reported ruthenium-and iridiumcatalyzed cross-coupling reactions between secondary benzylic alcohols and primary alcohols. [25] These results have demonstrated that alcohols can be used as promising green alkylating agents for the a-alkylation of ketones and balkylation of secondary alcohols.R ecently,t ransition-metalcatalyzed a-alkylation of ketones through aB Hp athway has aroused considerable attention as an efficient and atomeconomical method for constructing aC À Cb ond, and it allows convenient introduction of an alkyl group to the a-position of ketones with water formed as the only byproduct.…”

“…[25,44,45] The b-alkylation of secondary alcohols with primary alcohols in the presence of KOHa nd either aruthenium(II)-or iridium(III)/NHC complex catalyst is highly selective in forming the alcohol products 17 [Eq. (7)].…”

Ruthenium-catalyzed β-alkylation of secondary alcohols with primary alcohols

“…Previous studies have also revealed that the ligand environment around ruthenium can play a significant role in determining the catalytic activity of ruthenium complexes. For example, while RuCl 2 (PPh 3 )(2,2 0 :6 0 , 2 00 -terpyridine) effectively catalyzed the coupling reaction between PhCH(OH)Me with PhCH 2 OH, the complexes [(g 6 -cymene)RuCl 2 ] 2 and Cp ⁄ RuCl 2 are essentially inactive for the reaction [12]. These observations promoted us to investigate the catalytic properties of other ruthenium complexes with the intention of finding efficient catalytic systems for b-alkylation of alkyl-substituted secondary alcohols with primary alcohols.…”

“…Since then, a number of the ruthenium complexes have been tested for the reaction, including RuCl 2 (@CHPh)(PCy 3 ) 2 [20], [(g 6 -cymene)RuCl 2 ] 2 [12,20], RuCl 2 (DMSO) 4 [21], [(g 6 -C 6 H 6 )Ru(o-C 6 H 4 CH 2 NR 2 (NCMe)]PF 6 [22], [(g 6 -cymene)RuCl(pyrimidine-NHC)]PF 6 [13], RuCl 2 (PPh 3 )(2,2 0 :6 0 , 2 00 -terpyridine) [12], RuCl 3 (2,2 0 :6 0 ,2 00 -terpyridine) [12], Cp ⁄ RuCl 2 http://dx.doi.org/10.1016/j.ica.2015.03.023 0020-1693/Ó 2015 Elsevier B.V. All rights reserved. [12], (g 6 -cymene)ruthenium complexes supported by triazolidene [23] and cymene-ruthenium NHC [24], (NHC@imidazolin-2-ylidene, imidazolin-4-ylidene, and pyrazolin-3-ylidene) ligands, [CpRu(CH 3 CN)(PPh 3 ) 2 ]BF 4 [25], CpRuCl(PPh 3 ) 2 [25], CpRuCl(dppm) [25], [TpRu(CH 3 CN)(PPh 3 ) 2 ]BF 4 [25], TpRuCl(PPh 3 ) 2 [25] and cis-[Ru(H 2 O) 2 (6,6'Cl 2 bpy) 2 ](OTf) 2 [25].…”

“…Homogeneous catalysis based on soluble transition metals complexes [10] has also been actively explored for the transformation, for example, with complexes of metals such as Ir [11][12][13], Rh [4l,14] Pd [15], Cu [16], Ni [17], and Fe [18]. Another class of complexes that have been attracted much attention as potential catalysts for the transformation are ruthenium complexes.…”