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

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