Studies On The New Reactions Based On The Dual Roles Of Oxodiperoxovanadate And Tertiaryamine N-Oxide Both As A Nucleophile And An Oxidant

In organic chemistry, the oxidation of benzyl halides and benzyl alcohols to aromatic aldehydes and aromatic ketones is an important reaction and of great significance both in theory and in practice. There are numerous methods for the oxidation of benzyl halides to aldehydes or ketones, but no literature reported the green oxidation method in water as far as we know.This paper is composed of two parts based on the dual roles of oxodiper- oxovanadate and tertiaryamine N-oxide both as a nucleophile and an oxidant in the oxidation of benzyl halides or benzyl alcohols to aldehydes and ketones. Part Ⅰ Oxidation of benzyl halides to aldehydes and ketones with V2O5-H2O2A variety of benzyl halides were oxidated to aldehydes, reaction time 5~24 h, yield 80~98％. Oxidation of p-ClC6H4CH2Cl was scaled up and the aqueous phase was reused for the subsequent oxidation. For the eight subsequent oxidations, the catalytic efficiency remained unchanged.Reaction mechanism was proposed. V2O5 reacted with H2O2 giving VO(O2)2－, which is transferred into organic phase by PTC and then substitute halide atoms, converting benzyl halides to aldehydes or ketones. VO(O2)2－ is reduced to V2O5, forming a catalytic circle(Scheme 2).Factors influencing the reaction were analysed, including steric effect, nature of the leaving group, quantity of V2O5 and pH values.The new green method for the oxidation of benzyl halides to aromatic aldehydes or ketones we discovered has the following advantages compared with literature means:1 Environmental friendly water is used as reaction medium instead of organic solvents. To the best of our knowledge, there is no green oxidation for benzyl halide up to date. Water as reaction medium avoids volatilizing organic solvents, which are harmful to health and environment. In addition, costs of production are reduced.2 Catalysts (V2O5 and aliquat 336) are inexpensive, easily available, stable, and highly efficient(S/C=1000:5). In theory, the catalysts may be reused infinitely without losing its activity. While scaling up, we reused the catalysts for 8 times and no decline in efficiency was observed. 3 The oxidation is suited for a variety of functionalized benzyl halides(amides, esters, ethers, aryl halides, phenolic group). The reaction has good selectivity with aldehydes as the only product (no carboxylic acids). The conversion of benzyl chlorides to aromatic aldehydes is quantitative and the yields are more than 90%.Since water as reaction medium instead of organic solvents and the small amount of catalysts can be reused without limitations, recovery of solvents and catalysts is not a problem. At the end of reaction, only simple distillation is needed to obtain the product after separation of oil/water. In the subsequent operation, addition of 1.5 eq of hydrogen peroxide is enough for next cycle. Therefore, the operation is simple as for the whole reaction.The two byproducts of the reaction are water and hydrogen chloride. Water is the reaction medium and the accumulation of HCl provides acidic conditions to accelerate the reaction. So, no byproduct is let off. Our new green method represents the first green oxidation of benzyl halides and is an innovation to the oxidative theory of benzyl halides to aromatic aldehydes or ketones, which provides a good resolution to the problems existing in the process. PartⅡ Oxidation using tertiaryamine N-oxide(TMANO ) under acidic conditions .A new method was invented to convert benzyl alcohols to aldehydes and ketones with trimethylamine N-oxide under acidic conditions and. A variety of benzyl alcohols were oxidated to aldehydes and ketones, reaction time 15~48 h, yield 80~92％.Reaction mechanism was proposed (Scheme 3) and factors influencing the reaction were analysed , including steric effect, type of tertiaryamine N-oxide, electronic effect.The new reaction we invented enrichs the methods of oxidation of benzyl alcohols to aldehydes and ketones. Trimethylamine N-oxide is inexpensive and easily prepared, the conversion of or...