Exploring the Synthetic Versatility of the Lewis Acid Induced Decomposition Reaction of α-Diazo-β-hydroxy Esters. The Case of Ethyl Diazo(3-hydroxy-2-oxo-2,3-dihydro-1H-indol-3-yl)acetate

Ethyl diazo(3-hydroxy-2-oxo-2,3-dihydro-1H-indol-3-yl)acetate was prepared by aldol-type condensation of ethyl diazoacetate with isatin. A systematic and mechanistic study on the Lewis acid induced decomposition reaction of this valuable diazo precursor was carried out with the aim to gain new insights into the mechanistic aspects of the reaction as well as to further understand the factors and experimental conditions which affect the relative product distribution. The reaction, which may proceed via cationic and noncationic mechanisms, was found to be significantly influenced by the reaction environment determined by the characteristics of the Lewis acid employed, by the ability of the Lewis acid to form a complex with the alcohol functionality of the alpha-diazo-beta-hydroxy ester, and by the polarity and nucleophilicity of the solvent used.