α-Alkoxyacrylic acids from α-ketoacids.

Abstract

Dianions were made for the first time from α-ketoacids, using n-BuLi/t-BuOK (Lochmann's base), and alkylated on oxygen with dialkyl sulfates, alkyl sulfonates (triflates, tosylates), or alkyl halides to produce α-alkoxyacrylic acids. This is a more direct and efficient route to these acids than those used earlier. The α -ketoacids used were pyruvic acid, 2-oxobutanoic acid, and 3-methyl-2-oxobutanoic acid. 2-Oxobutanoic acid gave (Z)-2-alkoxy-2-butenoic acids with very high stereoselectivity. 3-Methyl-2-oxobutanoic acid gave 3-methyl-2-alkoxy-2-butenoic acids in low yields, but this is the only route to these acids to date.