Synthetic Scope of Ru(OH)_x/Al₂O₃‐Catalyzed Hydrogen‐Transfer Reactions: An Application to Reduction of Allylic Alcohols by a Sequential Process of Isomerization/Meerwein–Ponndorf–Verley‐Type Reduction

Abstract

Reduction of allylic alcohols can be promoted efficiently by the supported ruthenium catalyst Ru(OH)x/Al2O3. Various allylic alcohols were converted to saturated alcohols in excellent yields by using 2-propanol without any additives. This Ru(OH)x/Al2O3-catalyzed reduction of a dienol proceeds only at the allylic double bond to afford the corresponding enol, and chemoselective isomerization and reduction can be realized under similar conditions. The catalysis is truly heterogeneous and the high catalytic performance can be maintained during at least three recycles of the Ru(OH)x/Al2O3 catalyst. The transformation of allylic alcohols to saturated alcohols consists of three sequential reactions: oxidation of allylic alcohols to alpha,beta-unsaturated carbonyl compounds; reduction of alpha,beta-unsaturated carbonyl compounds to saturated carbonyl compounds; and reduction of saturated carbonyl compounds to saturated alcohols.

Catalytic transfer hydrogenation of levulinate esters to γ-valerolactone over supported ruthenium hydroxide catalysts

“…47,48 In the present catalytic system, GVL was produced through sequential CTH and dealcoholation reactions, being catalyzed by ruthenium hydroxide and basic sites of oxides, respectively. Ru is the cheapest metal among noble metals, and its hydroxide form is expected to act as an efficient heterogeneous catalyst for this reaction owing to its approved catalytic ability in the CTH reaction of carbonyl compounds.…”

Highly Dispersed Ruthenium Hydroxide Supported on Titanium Oxide Effective for Liquid‐Phase Hydrogen‐Transfer Reactions

“…[1] Our strategy to design efficient heterogeneous catalysts for various functional group transformations is the creation of metal hydroxide species on the appropriate supports. [2][3][4][5] The metal hydroxide ). Characterizations with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR), and X-ray absorption fine structure (XAFS) showed the presence of monomeric rutheniumA C H T U N G T R E N N U N G (III) hydroxide and polymeric rutheniumA C H T U N G T R E N N U N G (III) hydroxide species.…”

“…To the best of our knowledge, there are few examples of the heterogeneously catalyzed racemization of alcohols and amines [2,10] and only one example of the selective reduction of allylic alcohols with an alcohol as the hydrogen source. [3] We prepared three kinds of supported ruthenium hydroxide catalysts with different TiO 2 supports: Ru(OH) x / TiO 2 (A), Ru(OH) x /TiO 2 (B), and Ru(OH) x /TiO 2 (C) (see later section), and these catalysts could act as efficient, reusable heterogeneous catalysts for various hydrogen-transfer reactions, such as the racemization of chiral secondary alcohols [Eq. (1)], as well as the reduction of carbonyl compounds [Eq.…”

“…In particular, the highly dispersed ruthenium hydroxide species supported on high-surface area TiO 2 , Ru(OH) x /TiO 2 (A), showed very high catalytic activity for these hydrogen-transfer reactions-much higher than those of the previously reported heterogeneous catalysts including Ru(OH) x /Al 2 O 3 . [2,3] Herein, we report the characterization of these supported ruthenium catalysts, the scope of the above-mentioned transformations, and the relationship between the catalytic activities and the structure of the active sites in detail. The BET surface areas of the supported ruthenium hydroxide catalysts were very close to those of the parent supports ( Table 1).…”

Efficient Aerobic Ruthenium‐Catalyzed Oxidation of Secondary Alcohols by the Use of a Hybrid Electron Transfer Catalyst

“…[18] All other reagents are commercially available and were used without further purification. Column chromatography was performed with DAVISIL LC60A silica gel and analytical TLC was performed on Merck precoated silica 60-F 254 plates.…”