Phenyliodonium Zwitterion as an Efficient Electrophile in the Palladium-Catalyzed Suzuki-Type Reaction: A Novel Method for the Synthesis of 3-Aryl-4-hydroxycoumarins
摘要:
A palladium-catalyzed coupling reaction of phenyliodonium zwitterions with aryl boronic acids has been developed. The unique characteristics of the mild reaction conditions and convenient synthetic accessibility of phenyliodonium zwitterions make this method a valuable tool for generating diversified 3-aryl-4-hydroxycoumarins.
We herein report the simple and direct arylation of 4-hydroxycoumarins by photoinduced reaction with aryl halides (iodobenzene, iodonaphthalene, 4-iodoanisole, 2-iodoanisole). Good yields of 3,4-disubstituted coumarins were obtained in these reactions (>60%). Extension of the procedure to the reaction with o-dihalobenzenes leads to the synthesis of ring closure products which bear a tetracyclic aromatic-condensed ring system, although in lower overall yields (approximate to 45%). (C) 2010 Elsevier Ltd. All rights reserved.