Long-range correlations (nj C,H n > 3) in the HMBC spectra of 3-(4-oxo-4H-chromen-3-YL)-acrylic acid ethyl esters

Abstract

A systematic study about the long-range correlations observed in the HMBC spectra of a series of cis and trans 3-(4-oxo-4H-chromen-3-yl)-acrylic acid ethyl esters, and 5-hydroxy derivatives, was carried out. The results were compared with those observed in IMPEACH-MBC and CIGARHMBC spectra. An uncommon 5JC,H between the methyl protons and the C α to the carbonyl group was observed in these systems as well as in ethyl chrotonate. The complete assignments of the 1H and 13C NMR spectra are provided. ©2005 Sociedade Brasileira de Química.