Synthesis of Trifunctionalized Naphtho[1,2- b]furans Based on the Strategy for the Construction of Both Furan and Naphthalene Cycle.

Pd(PPh3)2Cl2-catalyzed selective tandem cyclization/oxidation of available conjugated diazo ene-yne-ketones under O2 atmosphere led to the formation of diazo trisubstituted furans. The Rh2(OAc)4-mediated selective C(sp2)-H insertion at the ortho-position of 2-aryl group (R1) of the furan moiety under N2 atmosphere occurred to construct naphthalene cycle, affording trifunctionalized naphtho[1,2- b]furans. C(sp2)-H insertion at the 4-position of the furan ring, and Wolf rearrangement of diazo moiety have not been observed.