Preparation of 2-amino-4H-chromene derivatives from coumarins under basic media

The reaction of coumarin with cyanoacetate derivatives in the presence of a nucleophilic base (alkoxides or piperidine) follows an interesting pathway that involves both a coumarin skeletal rearrangement and a Michael addition, via a coumaric acid derivative, to afford a substituted 4H-chromene skeleton. The particular behavior of this process influences the performance and the type of compounds that can be obtained. We demonstrate that the use of an excess of cyanoacetate affords the 4H-chromene derivative in high yield. An explanation of the mechanism involved in this process is proposed.