Structure elucidation of acetylation products of 2-acyl-1,3-indanediones by correlation of infrared spectral data

2-(1-Acetoxyalkylidene)- and 2-(1-acetoxybenzylidene)-1,3-indanediones (1a–1e) were proven to be the products of acetylation of 2-acyl-1,3-indanediones (2a–2e) by ketene using a detailed investigation and correlation analysis of infrared spectral data as well as1H-NMR and13C-NMR spectra. Study by means of CNDO/2 and MMPI methods also demonstrates that the structure1 is more stable as the alternative one of 2-acyl-3-acetoxy-2-indene-1-ones (5). It was shown that the recently proposed general correlations v(C=O)s vs. v(C=O)as and v(C=O) vs. ∑X+(R) as well as the mechanical anharmonicities of asymmetric C=O stretching vibration can be successfully used as a tool of structural diagnostics of cyclic 1,3-dicarbonyl compounds.