N-Heterocyclic carbene-catalysed homoenolate addition reaction to 3-cyano-2-imino-2 H -chromenes: synthesis of C 4 -functionalized 2-amino-3-cyano-4 H -chromene

A diastereoselective N-heterocyclic carbene-catalysed reaction between enal and 3-cyano-2-imino-2 -chromene is described for accessing a new type of C -functionalized 2-amino-3-cyano-4 -chromene. A wide variety of enals and iminochromenes afforded the desired homoenolate addition product 2-amino-4 -chromenes in good yields and with moderate to good diastereoselectivities.