1,2-Nucleophilic addition on 2-phenyl-3H-indol-3-one and 2-phenyl-3-phenylimino-3H-indole and their corresponding 1-oxides. An attempt to synthesize water-soluble aminoxyls. Crystal structure of 3-ethoxycarbonyl-2,3,3a,4-tetrahydro-2,4-dioxo-3a-phenylisoxazolo[2,3-a]indole

Abstract

3-Indolinonic (1a) and 3-phenyliminoindolinonic (1b) 1-oxides react at carbon 2 with diethyl malonate and ethyl acetoacetate anions, yielding intermediate anions which undergo cyclization in the reaction medium to form an isoxazolidine ring. The cyclization occurs through the interaction of the oxygen of the primitive N-oxide function with a carbonyl group of the reagents. The same substrates react with dilithium phenylacetate anion, leading to the formation of stable and water-soluble carboxylated aminoxyls. The indolenin-3-one 2a and its corresponding 3-phenylimino derivative 2b also react with the above-mentioned nucleophiles to form carboxylated 3-indoxyls without cyclization; oxidation with m-chloroperbenzoic acid does not yield carboxylated aminoxyls in appreciable amount. The structure of the product of cycloaddition obtained from the reaction of compound 1a with diethyl malonate was determined by X-ray analysis.