Nucleophilic vinylic substitution of halocoumarins and halo-l,4-naphthoquinones with morpholine

Reactions of morpholine with 4-halocoumarins 1 , 3-halocoumarins 3 , and 2-halo-l,4-naphthoquinones 8 yield two different products, one where halogen is replaced by a nucleophile at the same carbon and the other where the nucleophile is attached to the vicinal carbon away from that bearing the halogen. It is considered that reactions proceeds through nucleophilic vinylic substitution by comparision of the reaction products and deuterium exchange experiments. Plausible mechanisms for these routes are suggested.