Formation and X-ray crystal structure of ethyl 2-amino-1-oxo-inden-3-carboxylate

Abstract

Treatment of 2-acetyl-4-chloro-1 -cyano-1,2,3,4-tetrahydro-3-hydroxyisoquinoline (1) with ethanolic sodium hydroxide gave 1-ethoxy-3-methylisoquinoline-4-carbaldehyde (2) accompanied by a purple by-product identified as ethyl 2-amino-1-oxoindene-3-carboxylate (3). The structure of compound (3), the first example of a simple 1-aminoindenone, was confirmed by synthesis from the homophthalic ester (5) and by an X-ray crystallographic analysis. The mechanism of the conversion, (1)→(3), is briefly discussed.