An effective use of benzoic anhydride and its derivatives for the synthesis of carboxylic esters and lactones - Powerful and convenient mixed anhydride methods promoted by lewis acids or basic catalysts

Efficient methods for the synthesis of carboxylic esters and lactones using benzoic anhydrides by the promotion of Lewis acid or basic catalyst is accounted in this paper. Various carboxylic esters are prepared in high yields through the formation of the corresponding mixed anhydrides from 4-(trifluoromethyl)benzoic anhydride (TFBA) and carboxylic acids in the presence of Lewis acid catalyst. Several macrolactones and medium-sized lactones are also prepared from the corresponding hydroxycarboxylic acids by the combined use of TFBA and an acidic species under the mild reaction conditions. Furthermore, a variety of carboxylic esters or lactones are obtained at room temperature in excellent yields with high chemoselectivities from nearly equimolar amounts of carboxylic acids and alcohols, or hydroxycarboxylic acids using 2-methyl-6-nitrobenzoic anhydride (MNBA) with basic promoters. These methods are successfully applied to the synthesis of 8-membered ring lactone moieties of cephalosporolide D, and octalactins A and B.