Two-Step, Practical, and Diversity-Oriented Synthesis of Multisubstituted Benzofurans from Phenols through Pummerer Annulation Followed by Cross-coupling
Two-Step, Practical, and Diversity-Oriented Synthesis of Multisubstituted Benzofurans from Phenols through Pummerer Annulation Followed by Cross-coupling
作者:Kei Murakami、Hideki Yorimitsu、Atsuhiro Osuka
DOI:10.1246/bcsj.20140241
日期:2014.12.15
Practical and diversity-oriented synthesis of multisubstituted benzofurans has been accomplished from simple phenols through a Pummerer annulation/cross-coupling sequence. Operationally simple and rapid reactions of phenols with ketene dithioacetal monoxides (KDMs) with the aid of trifluoroacetic anhydride provide the corresponding 2-methylsulfanylbenzo[b]furans. The scope of the reaction encompasses phenols and KDMs having a broad range of substituents. The remaining methylsulfanyl group in the annulation products is converted to various aryl groups through cross-coupling reactions that we improved specially to this end. This two-step approach to multisubstituted benzofurans is powerful enough to synthesize highly fluorescent benzofuran derivatives as well as the naturally occurring Eupomatenoid family.