Investigation of the selective reduction of isatin derivatives. Synthesis of α-hydroxyacetophenone derivatives and ethyl spiro-3,3-(ethylenedioxy)-2-hydroxyindoline carboxylates

The product from the reduction of ethyl spiro-3,3-(ethylenedioxy)-2-oxindole carboxylates (1) using borohydride salts has been found to be dependant upon both solvent and metal ion. With polar solvents and lithium bromide/sodium borohydride, spiro-3,3-(ethylenedioxy)-2-hydroxyindole carboxylates (2) are obtained in high yields whilst [2-(2-hydroxymethyl-[1,3]dioxolan-2-yl)-phenyl]-carbamic acid ethyl esters (3) are obtained using sodium borohydride in less polar solvents.