Catalysis of Organic..

Tanielyan et al. 14117. Bromine-Free TEMPO-Based CatalystSystem for the Oxidation of Primary andSecondary Alcohols Using NaOCl as the OxidantSetrak K. Tanielyan 1 , Robert L. Augustine 1 , Indra Prakash 2 ,Kenneth E. Furlong 2 and Handley E. Jackson 21 Center for Applied Catalysis, Seton Hall University, South Orange, NJ 070792 The NutraSweet Corporation, Chicago, IL 60654Abstracttanielse@shu.eduOne of the most efficient methods for oxidation of primary alcohols to eitheraldehydes or carboxylic acids is the one, commonly known as the Anelli oxidation.This reaction is carried out in a two-phase (CH 2 Cl 2 /aq.buffer) system utilizingTEMPO/NaBr as a catalyst and NaOCl as the terminal oxidant The new systemdescribed here is an extension of the Anelli oxidation, but surprisingly, does notrequire the use of any organic solvents and replaces the KBr co-catalyst with themore benign, Na 2 BB4O 7 (Borax). The use of the new cocatalyst reduces the volume ofthe buffer solution and eliminates completely the need of a reaction solvent. Thenew system was successfully applied in the industrial synthesis of the 3,3-Dimethylbutanal, which is a key intermediate in the preparation of the new artificialsweetener Neotame.IntroductionThe selective oxidation of alcohols to the corresponding carbonyl compounds is oneof the more important transformations in synthetic organic chemistry. A largenumber of oxidants have been reported in the literature but most of them are basedon the use of transition metal oxides such as those of chromium and manganese(1,2). Since most of the oxidants and the products of their transformation are toxicspecies, their use creates serious problems concerning their handling and disposal.For these reasons, the search for an efficient, easily accessible catalysts and ”clean”oxidants such as hydrogen peroxide or molecular oxygen for industrial applicationsis still a challenge (3-6). A particularly convenient procedure for the oxidation ofprimary and secondary alcohols is reported by Anelli (4). The oxidation has beencarried out in a two-phase system (CH 2 Cl 2 -water) utilizing 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) as a catalyst, NaBr as a cocatalyst andcheap and readily accessible NaOCl as an oxidant. The aqueous phase is buffered atpH 8.5-9.5 using NaHCO 3 (Scheme 1). In another development of the sameprocedure, the ethyl acetate-toluene mixture has been used to replace the CH 2 Cl 2 (7)Despite the extensive work reported in the area of the selective oxidation ofprimary alcohols, there is still a continuous need for developing efficient and