Efficient Palladium‐Catalyzed CO Hydrogenolysis of Benzylic Alcohols and Aromatic Ketones with Polymethylhydrosiloxane

Abstract

Scheme 7. Possible explanation for the palladium-catalyzed reductive deoxygenation of aromatic alcohols and ketones.Scheme 8.

Palladium nanoparticles supported on reduced graphene oxide as an efficient catalyst for the reduction of benzyl alcohol compounds

“…For example, benzyl alcohol was reduced in 54% yield after 3 h using Pd/C catalyst in compressed CO 2 /water and 1 MPa H 2 [4]. Independently, Huang et al [5] obtained toluene in 98% yield through the reduction of benzyl alcohol using iridium catalyst with hydrazine at 160°C after 3 h. Wang et al [6] reported benzyl alcohol hydrogenolysis in 99% yield using PdCl 2 and PMHS after 12 h at 40°C.…”

“…It should be noted that this procedure allowed the reduction of benzyl alcohol derivatives in relatively short reaction times and mild conditions as compared to the methods described in the literature [4][5][6]. For example, benzyl alcohol was reduced in 54% yield after 3 h using Pd/C catalyst in compressed CO 2 /water and 1 MPa H 2 [4].…”

“…Since hydroxyl group is a poor leaving group, its transformation into a good leaving group is generally employed [3]. Several reagents and catalysts have been reported for the reduction of benzyl alcohols [4][5][6]. For example, Pd/C and H 2 in compressed CO 2 /water [4], iridium catalyst with hydrazine at 160°C [5], palladium chloride (PdCl 2 ) and polymethylhydrosiloxane (PMHS) as hydride source [6] have been investigated for this chemical transformation.…”

Advances in the Synthesis of Methylated Products through Indirect Approaches

“…Second, the oxidative addition of Pd(0) to benzylic alcohols to form the palladium hydride intermediate I , which reacts with HCl that is generated in the reaction mixture to afford the corresponding halogenated palladium intermediate II . Then, in the presence of a hydrogen source, the intermediate II further transforms into the hydrocarbons …”

Mild Deoxygenation of Aromatic Ketones and Aldehydes over Pd/C Using Polymethylhydrosiloxane as the Reducing Agent

“…[11] To date, several transition-metal-based catalytic protocols employing PMHS as the reducing agent have been developed for the reduction of amides to amines, [12] as well as for the conversion of ketones, aldehydes, and esters either into alcohols [13] or to saturated alkanes. [14] Although homogeneous systems for the deoxygenation of aromatic alcohols, aldehydes, and ketones with PMHS have been developed, [15,16] there exists no heterogeneous catalytic system for the deoxygenation of aromatic ketones and aldehydes under hydrosilylation conditions. Heterogeneous protocols are generally associated with several practical advantages, such as improved catalyst stability, simpler separation and purification procedures, possibility of catalyst recycling, and lower levels of metal impurities in the final product.…”