Novel pyrrolocoumarin derivatives

Abstract

Ethyl esters of 2-[(4`,7`-dimethyl-2`-oxo-2'H-1'-benzopyran-6`-yl)azo]-2-alkyl-3-oxobutanoic acids have been synthesized from diazotized 6-amino-4,7-dimethyl-2H-1-benzopyran-2-one.and ethyl esters of 2-alkyl-3-oxobutanoic acids in the presence of sodium acetate. The esters have then been transformed into indoles (obviously via intermediate hydrazones) by the Fischer reaction in the presence of acids. This is a way to novel class of indole derivatives -ethyl esters of 3,7-dihydro-7-oxopyrano[3,2-e]indol-2-carboxylic acids with different substituents. All the new compounds have been characterised by 1 H-NMR and mass spectra, and elemental analyses.