Cobalt Nanoparticles‐Catalyzed Widely Applicable Successive C−C Bond Cleavage in Alcohols to Access Esters

Abstract

Selective cleavage and functionalization of C À C bonds have important applications in organic synthesis and biomass utilization. However,functionalization of CÀCbonds by controlled cleavage remains difficult and challenging because they are inert. Herein, we describe an unprecedented efficient protocol for the breaking of successive C À Cbonds in alcohols to form esters with one or multiple carbon atoms less using heterogeneous cobalt nanoparticles as catalyst with dioxygen as the oxidant. Aw ide range of alcohols including inactive long-chain alkyl aryl alcohols undergo smoothly successive cleavage of adjacent À(CÀC) n À bonds to affordt he corresponding esters.T he catalyst was used for seven times without any decrease in activity.C haracterization and control experiments disclose that cobalt nanoparticles are responsible for the successive cleavage of C À Cb onds to achievee xcellent catalytic activity,w hile the presence of CoN x has just the opposite effect. Preliminary mechanistic studies reveal that atandem sequence reaction is involved in this process.

Multi-purpose heterogeneous catalyst material from an amorphous cobalt metal–organic framework

“…30 Typically, Co-N-C catalysts are used for reduction reactions (nitroarenes, 31,32 N-heterocycles, 33 and hydrocarbons 34 ), reductive aminations 35 and alkylations, 36,37 while the oxidative esterification of benzyl alcohols were done under dioxygen. [38][39][40] Overall, the cobalt materials outperformed the three previously reported related Fe-N-C systems (TAL-1-900, TAL-6-900, TAL-7-900), 22,23 and importantly, they sustained their activity over a larger number of cycles (Fig. 2A and B; Tables S6 and S7, ESI †).…”

Selectively Upgrading Lignin Derivatives to Carboxylates through Electrochemical Oxidative C(OH)−C Bond Cleavage by a Mn‐Doped Cobalt Oxyhydroxide Catalyst

“…The as‐prepared samples were initially evaluated for electrochemical oxidation of 1‐phenylethanol (denoted as 1 ), a typical lignin model compound with C(OH)‐C structure, [2b–d] in undivided cell with 1 M KOH electrolyte. As shown in Figure 2 a, the CV curve of MnCoOOH/NF shows the good OER activity in 1.0 M KOH electrolyte with an onset overpotential of 310 mV.…”

“…Notably, carbohydrates and lignin features C(OH)‐C motifs, [3] therefore providing a feasible route to carboxylic acids via selective C−C bonds cleavage (Scheme 1 b). In this respect, several thermocatalytic methods have been recently developed for aerobic oxidative cleavage of C(OH)−C bonds, achieving efficient transformation of lignin models to corresponding carboxylic acids [2b–d] . Nevertheless, these processes often require homogeneous catalysts (e.g., copper or vanadium) or toxic nitrogen oxides, and are operated at elevated temperature (Table S1) [2c,d, 4] .…”

Heterogeneous Cobalt‐Catalyzed C−C Bond Cleavage in Alcohols to Carbonyl Compounds

“…The energy barriers of most cleavage reactions are high, so the conditions are harsh. [24,26] Traditionally, people used stoichiometric quantities or even excessive oxidants for oxidative cleavage of CÀ C bond, such as chromium oxidants, sodium periodate, manganese dioxide, potassium permanganate, lead tetraacetate. Although the effect is ideal, it will bring a large number of environmental pollutants, which does not meet the requirements of green chemistry.…”

“…However, the potassium carbonate was necessary, otherwise the reaction cannot be occurred. Dai et al [26] demonstrated Co-NC catalyst system for the continuous cleavage of CÀ C bond in primary and secondary alcohol to corresponding ester with high selectivity. And the catalytic system was suitable for various functionality aromatic, aliphatic, heterocyclic, allyl, propargylic primary and secondary alcohols as well as inactive long chain alkyl aryl alcohols, but high temperature and pressure and excessive alkali were necessary (Scheme 1).…”