A Strategy to Avoid Anomalous O‐Alkylation of 4‐Hydroxyindole by Diethyl Bromomalonate.

Abstract

Alkylation of 4-hydroxyindole with diethyl bromomalonate under standard conditions (potassium carbonate−acetone) gave the expected indolyloxymalonate ester 3 together with the anomalous indolyloxy-2-bromomalonate 4. Depending on conditions, the ratio of the two products varied between 4:1 and 1:2. Protection of the indole nitrogen by a carbobenzyloxy group eliminated formation of the anomalous product.