| Abstract
| - The boron-mediated aldol reaction of carboxylic esters is described in detail. Contrary to the generalbelief that carboxylic esters are inert under the condition of the boron enolate formation, propionateesters are enolized with certain combinations of a boron triflate and an amine. More importantly,the stereochemical course of the aldol reaction can be controlled by the judicious selection of theenolization reagents. Treatment of propionate esters with c-Hex2BOTf and triethylamine producesanti-aldol products, and that with Bu2BOTf and diisopropylethylamine gives syn-aldol productsselectively after reaction with aldehydes. Complementary anti- and syn-selective asymmetric aldolreactions with structurally related, readily available chiral norephedrine-derived propionate estersare developed.
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