4-Chlorocoumarin-3-carboxaldehyde (1) and 4-chloro-3-(g, g-dicyanoethenylidene) coumarin (2) produce their respective 1: 1 phosphonate adducts (5a-c) and (6a-c) upon reaction with the appropriate dialkylphosphonates (3a-c). Compounds 5 undergo dechlorination and dephosphorylation upon reaction with certain primary aliphatic amines to yield 9 (or 10) according to the nature of the amine used. Compounds 1 and 2 undergo ...