Highly Efficient Etherification and Oxidation of Aromatic Alcohols Using Supported and Unsupported Phosphorus Pentoxide as a Heterogeneous Reagent

Abstract

A highly efficient procedure for etherification and oxidation of aromatic alcohol is described using unsupported and supported P 2 O 5 on alumina and/or silica gel. The silica gel and alumina proved to be the most suitable support among the supports examined in our experiments. It was illustrated that the etherification and oxidative performance in reactions depend largely upon variables including reaction temperature, the nature of the P 2 O 5 used (supported or unsupported P 2 O 5 ), and whether solvent-free conditions are applied. It was shown that P 2 O 5 not only can convert the aromatic alcohols into corresponding ethers and/or aldehyde and ketone but also can convert aromatic ethers into aldehyde or ketone via oxidative cleavage. Finally, quantum mechanical calculations were performed to rationalized these events, and it was indicated that aldehyde and ketone are more favorable products on the basis of the heat of formation (DH f ).

P-Doped Porous Carbon as Metal Free Catalysts for Selective Aerobic Oxidation with an Unexpected Mechanism

“…( 6) In addition, the reaction is associated with loss of water when reaction was performed under oxygen as demonstrated by the presence of water peak in 1 H NMR spectroscopy of the final product mixture (Figure S13). On the basis of these findings and previous reports using P 2 O 5 to accelerate the oxidation of alcohols 50 and carbohydrates, 51 and especially, a recent finding suggesting the importance of ketonic O in catalysis of benzylic alcohol oxidation, 52 we propose the following mechanism as shown in Scheme 2 where primary benzyl alcohol is used as an example. In the first step of catalysis, condensation between the alcohol and PO moieties on PGc takes place, and an alcoholate intermediate is formed.…”

Organocatalytic Asymmetric Peroxidation of γ,δ-Unsaturated β-Keto Esters—A Novel Route to Chiral Cycloperoxides

“…In a similar vein, Khazaei and colleagues have previously Given the Lewis acidic nature of phosphorus pentoxide, it is likely that the reaction proceeds in a manner similar to that of our previously established silver-mediated cyclisation of tert-butylperoxyalkyl bromides, i.e., by trapping of the oxygen lone pair by the incipient carbocation, resulting in loss of the tert-butyl group and formation of the target cycloperoxide (Figure 3) [18,40]. In a similar vein, Khazaei and colleagues have previously demonstrated the use of phosphorus pentoxide for the etherification of benzylic alcohols [63]. Given the Lewis acidic nature of phosphorus pentoxide, it is likely that the reaction proceeds in a manner similar to that of our previously established silver-mediated cyclisation of tert-butylperoxyalkyl bromides, i.e., by trapping of the oxygen lone pair by the incipient carbocation, resulting in loss of the tert-butyl group and formation of the target cycloperoxide (Figure 3) [18,40].…”

“…Given the Lewis acidic nature of phosphorus pentoxide, it is likely that the reaction proceeds in a manner similar to that of our previously established silver-mediated cyclisation of tert-butylperoxyalkyl bromides, i.e., by trapping of the oxygen lone pair by the incipient carbocation, resulting in loss of the tert-butyl group and formation of the target cycloperoxide (Figure 3) [18,40]. In a similar vein, Khazaei and colleagues have previously demonstrated the use of phosphorus pentoxide for the etherification of benzylic alcohols [63].…”