Selective oxidation of methyl mandelate to methyl phenyl glyoxylate using liquid–liquid–liquid phase transfer catalysis

The conversion of the traditional liquid–liquid (L–L) phase transfer catalysis (PTC) into liquid–liquid–liquid (L–L–L) PTC offers several advantages. L–L–L PTC is a novel strategy which offers catalyst recovery, waste reduction including better selectivity and improving profitability. The middle catalyst-rich phase formed between the other two phases is the locale of main reaction and it intensifies the rates of reaction by order of magnitude. In the current work, oxidation of methyl mandelate to methyl phenyl glyoxylate has been studied by using L–L–L PTC with tetra-butyl ammonium bromide as a catalyst at 45 °C. It leads to 100% selectivity towards methyl phenyl glyoxylate within very short reaction time. The method offers several advantages including catalyst separation and reusability. The effects of different parameters were studied in detail. A mathematical model is developed and validated with the observed reaction data