4 - [Bis(acyloxy)iodo]benzenes

Abstract

This chapter explores [Bis(acyloxy)iodo]benzenes (BTI) and is divided into two sections. The first section deals with [bis- (trifluoroacetoxy)iodo]benzene, a powerful oxidant and a versatile electrophile with many synthetic applications; emphasis is placed on reactions not realized by its acetoxy analogue, as discussed in the previous chapters. The second section examines some of the reactions of its perfluoro analogue and mainly reactions common to a number of [bis(acyloxy)iodo]benzenes generated from a wide range of carboxylic acids. Ethynyl groups attached to various skeletons were generally oxidized to the hydroxyacetyl functionality. The reaction was useful in the synthesis of natural products and analogues with a dihydroxyacetone side-chain. In contrast to (diacetoxyiodo)benzene, BTI reacts in aqueous solvents with both terminal and nonterminal alkynes affording α-hydroxyketones and 1,2-diketones, respectively. BTI is suitable for the direct hydroxylation of ketones. The primary reaction of terminal alkynes leads to the formation of alkynyl phenyliodonium salts, which are not isolable under experimental conditions, but have been prepared by other routes. Nonterminal diarylacetylenes have been oxidized by BTI to α-diketones; good yields were obtained only from precursors containing electron donating groups or halogens.