Synthesis of 6H-dibenzo[b,d]pyran-6-ones from aryl 3-bromopropenoates via a sequential one-pot procedure using the sonogashira coupling-benzannulation reaction

Various kinds of 6H-dibenzo [b,d] pyran-6-ones 4 were synthesized via a sequential one-pot procedure using the Sonogashira coupling-benzannulation reaction of aryl 3-bromopropenoates 1, in which the ortho-position of aryl group is substituted with enynes or iodine, with acetylenes 2 in the presence of palladium and copper catalysts. The Sonogashira coupling between the aryl 3-bromopropenoates 1a and 1b, bearing enynes at the ortho-position of aryl group, and alkynes 2a-g gave the enyne intermediates 3 in situ, which subsequently underwent the palladium-catalyzed benzannulation reaction to afford the 6H-dibenzo [b,d] pyran-6-ones 5a-g and 6. The Sonogashira coupling between the aryl 3-bromopropenoate le, bearing iodine at the ortho-position of aryl group, and diynes 2f and 2h produced the diyne intermediates 13, which underwent the benzannulation reaction to afford the 6H-dibenzo[b,d]pyran-6-ones 14f and 14h.