Ruthenium‐Catalyzed β‐Alkylation of Secondary Alcohols with Primary Alcohols

Abstract

Cyclopentadienyl (Cp), hydrotris(pyrazolyl)borato (Tp), and bipyridine ruthenium complexes were found to be active catalysts for the b-alkylation of secondary alcohols with primary alcohols. Mechanistic aspects of the Cp and Tp complexes-catalyzed reactions were investigated; the crucial hydrido complexes were identified. Carbonyl complexes resulting from aldehyde decarbonylation were formed in some cases, and surprisingly, they were also found to be active for the catalytic processes.

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

“…For comparison, we have also carried out catalytic reactions with complexes RuCl 2 (PPh 3 ) 2 [25], RuCl 2 (DMSO) 4 [25], CpRuCl(PPh 3 ) 2 [25] and RuCl 2 (PPh 3 )(2,2 0 :6 0 ,2 00 -terpyridine) [12], which were previously reported to be catalytically active for the reaction. As shown in entries 18-21, Table 1, these complexes are less effective than RuCl 2 (PPh 3 ) 2 (2-NH 2 CH 2 Py) under similar reaction condition.…”

“…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].…”

“…Cho showed that the ruthenium complex RuCl 2 (PPh 3 ) 3 (5 mol%, 300% KOH, 80°C, 40 h) catalyzed b-alkylation of RCH(OH)Me (R = CH 3 (CH 2 ) 4 , Ph(CH 2 ) 2 , Me 2 CH) with PhCH 2 CH 2 OH in the presence of the hydrogen acceptor 1-dodecene to give RCH(OH)CH 2 CH 2 CH 2 Ph in low or moderate yields (23-58%) [19]. Lau et al showed that only trace amounts of the expected coupling products were obtained in the reactions of RCH(OH)Me (R = CH 3 (CH 2 ) 4 , Ph(CH 2 ) 2 ) with PrCH 2 OH catalyzed by complexes such as CpRuCl(PPh 3 ) 2 , CpRuCl(dppm) and cis-[Ru(H 2 O) 2 (6,6 0 Cl 2 bpy) 2 ](OTf) 2 (0.4 mol%, 120°C, 20 h) [25]. Previous studies have also revealed that the ligand environment around ruthenium can play a significant role in determining the catalytic activity of ruthenium complexes.…”

Direct Au-Ni/Al 2 O 3 catalysed cross-condensation of ethanol with isopropanol into pentanol-2

“…The fermentation mixture of the IBE conversion also did not lead to C 5 product formation. The condensation of secondary alcohols with primary alcohols thus effectively catalysed by homogeneous base and homogeneous/heterogeneous transition metal systems [9,27,28] but never a pure heterogeneous catalytic system.…”

Theoretical investigation on the mechanism of ferrocenecarboxaldehyde-catalyzed direct β-alkylation of 1-phenylethanol with benzyl alcohol

“…In the past few years, several teams have introduced some examples [7][8][9][10][11][12][13][14] of higher alcohols being produced directly by two alcohols and the only byproduct is water.…”