Abnormal Behavior of Coumarin Derivatives towards IR Spectroscopy

Abstract

The reaction of different coumarin-4-acetic acids with benzaldehyde gives different 4-styrylcoumarin. The reaction of 4-styrylcoumarins with tetracyanoethylene gives 7,7,8,8-tetracyano-3-substituted-9-phenyl-7,8,9,10-tetrahydro-6H-dibenzo[b,d]pyran-6-ones. These Diels-Alder adducts shows combined IR frequency for four nitrile groups in the range of 2253 to 2255 cm-1. Under the same conditions different coumarin-4-acetic acids are reacted with 7-diethylaminocoumarin-3-carbaldehyde to give 1,2-biscoumarinylethenes. The Diels-Alder reaction of these 1,2-biscoumarinylethenes with tetracyanoethylene gives 7,7,8,8-tetracyano-3-substituted-9-(7-diethylaminocoumarin-3-yl)-7,8,9,10-tetrahydro-6H-dibenzo [b,d]pyran-6-one. Latter Diels-Alder adducts does not show any absorption frequency for nitrile group in their IR spectrum.