Secondary alcohols oxidation with hydrogen peroxide catalyzed by [n-C16H33N(CH3)3]3PW12O40: Transform-and-retransform process between catalytic precursor and catalytic activity species

[n-C16H33N(CH3)3]3PW12O40 (1a) catalyzed the oxidation of secondary alcohols with 27.5% aqueous hydrogen peroxide under solvent-free conditions. The isolated yields of all ketones were higher than 92%. The turnover number of the catalyst 1a was above 368, and the highest TON and TOF were up to 3840 and 320 h−1. In this catalytic system, the catalytic active species was {PO4[WO(O2)2]4}3−, which was formed from 1a in the reaction. It was discovered that {PO4[WO(O2)2]4}3− (PW4) and [PW12O40]3− (PW12) kept an equilibrium during the alcohol oxidation by simultaneous monitoring the distribution of species in organic and aqueous phases. The analysis of the W content in the aqueous phase by ICP and the detection of the species transformation in the organic phase by 31P NMR revealed that the most of the PW4 species were transformed to the PW12 species again after the reaction. PW12 and PW4 were in the transform-and-retransform process.

A new transform-and-retransform process was first discovered between [PW12O40]3− and {PO4[WO(O2)2]4}3− in alcohol oxidation catalyzed by 12-phosphotungstate. The PW4 was formed from PW12 by reacting with H2O2, PW4 and PW12 kept equilibrium during reaction, and the most of PW4 could transform to PW12 again after reaction.Figure optionsDownload as PowerPoint slide