BISMUTH DERIVATIVES FOR THE OXIDATION OF ORGANIC-COMPOUNDS

This review deals with the utilization of bismuth compounds in oxidati on reactions of organic derivatives, Both the pentavalent and trivalen t states of bismuth were found to display oxidizing power. Inorganic b ismuth reagents, such as sodium bismuthate, zinc bismuthate and bismut h trioxide, have been employed, normally under acidic conditions, to e ffect glycol cleavage and specific oxidations of alcohols to their car bonyl compounds. Unlike these reagents, pantavalent triarylbismuth(V) is used under mild conditions of temperature and pH. Excellent yields of aldehydes and ketones were obtained from a variety of hydroxy conta ining compounds. Further, the oxidation of allylic alcohols by mu-oxob is(chlorotriphenylbismuth) was shown to be a particularly easy process . These transformations require stoechiometric amounts of the Bi(V) re agent and involve the Bi(V)/Bi(III) redox couple. This system could be made catalytic by using N-bromosuccinimide as the oxidant of BiPh(3) thus promoting the catalytic cleavage of alpha-glycols by Bi(V). A new class of bismuth oxidation catalysts was described recently, based on functionalized bismuth(III) carboxylates (alpha-hydroxycarboxylates, pyridine- and pyrazine-carboxylates, salicylates, aminosalycilates). T hus, Bi(III) mandelate, [(mand)(2)Bi(mu-O)Bi(mand)(2)], was found to b e an efficient catalyst for the oxidative C-C bond cleavage of epoxide s and their transformation into carboxylic acids in anhydrous DMSO med ium. Further, oxygen was found to be the oxidant in the Bi(III) carbox ylate-catalyzed oxidative transformation of alpha-ketols to carboxylic acids and in the conversion of 1-octene in octanones by the Rh(III) o r Pd(II)/BiCl3/LiCl systems.