Bismuth derivatives for the oxidation of organic compounds

Abstract

This review deals with the utilization of bismuth compounds in oxidation reactions of organic derivatives. Both the pentavalent and trivalent states of bismuth were found to display oxidizing power. Inorganic bismuth reagents, such as sodium bismuthate, zinc bismuthate and bismuth trioxide, have been employed, normally under acidic conditions, to effect glycol cleavage and specific oxidations of alcohols to their carbonyl compounds. Unlike these reagents, pentavalent triarylbismuth(V) is used under mild conditions of temperature and pH. Excellent yields of aldehydes and ketones were obtained from a variety of hydroxy containing compounds. Further, the oxidation of allylic alcohols by μ-oxobis(chlorotriphenylbismuth) was shown to be a particularly easy process. These transformations require stoechiometric amounts of the Bi(V) reagent 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 α-glycols by Bi(V). A new class of bismuth oxidation catalysts was described recently, based on functionalized bismuth(III) carboxylates (α-hydroxycarboxylates, pyridine- and pyrazine-carboxylates, salicylates, aminosalycilates). Thus, Bi(III) mandelate, [(mand) 2Bi(μ-O)Bi(mand) 2], was found to be an efficient catalyst for the oxidative CC bond cleavage of epoxides and their transformation into carboxylic acids in anhydrous DMSO medium. Further, oxygen was found to be the oxidant in the Bi(III) carboxylate-catalyzed oxidative transformation of α-ketols to carboxylic acids and in the conversion of l-octene in octanones by the Rh(III) or Pd(II)/BiCl 3/LiCl systems.