Synthesis of Nigricanin via Intramolecular Biaryl Coupling Reaction of Functionalized Phenol Benzoate

Abstract

A tetracyclic natural product, nigricanin (1), was synthesized through an intramolecular biaryl coupling reaction of the phenyl benzoate derivative which was derived from the corresponding phenol and benzoic acid.

Synthesis of Chloro-Substituted 6<i>H</i>-Dibenzo[<i>b</i>,<i>d</i>]pyran-6-one Natural Products, Graphislactone G, and Palmariols A and B

“…On the contrary, using Ag 2 CO 3 as the base, only a low selectivity was observed (run 4). 29,30) In order to validate the effect of the chlorine atom of 12, the previously reported results are shown in Table 1. 42) The substrate 14, which possesses no chlorine atom on the aromatic ring, was subjected to the same conditions as runs 1-4 listed in Table 1.…”

“…oxygen must be considered. 29,46) Due to the tight coordination, a severe steric hindrance is assumed around the chlorosubstituent. This steric factor will make the transition state B significantly disfavored.…”

“…We have reported several natural product syntheses using the Pd-mediated intramolecular biaryl coupling reaction [23][24][25][26][27][28][29][30][31] with phenyl benzoate derivatives for forming the 6Hdibenzo [b,d] pyran-6-one ring system. [32][33][34][35][36][37][38][39][40] Utilizing this transformation, we planned the efficient syntheses of 1, 2, and 3.…”