Cu(II)-Catalyzed [3 + 1 + 1 + 1] Cyclization of 1,3-Diketones and 2-Naphthols Using N , N -Dimethylethanolamine as a Dual Carbon Synthon for the Synthesis of 2 H -Chromenes.

Reactions with diverse C1 synthons to realize homologation were well explored. However, homologations occurring twice with one C1 synthon in a reaction were less reported. We disclose herein a Cu(II)-catalyzed novel and efficient synthesis of 2 H -chromenes from 2-naphthols, 1,3-diketones, and N , N -dimethylethanolamine (DMEA) as a dual carbon synthon. Various 2 H -chromenes with different functional groups are constructed in moderate to good yields. This is the first report that DMEA acts as a dual C1 synthon.