Improved synthesis of 4-phenylphenalenones: the case of isoanigorufone and structural analogs

Abstract

2-Hydroxy-4-phenyl-1H-phenalen-1-one (isoanigorufone, 1), a phytoalexin exclusive of Musaceae, was synthesized starting from 3-(2-hydroxynaphthalen-1-yl)propanenitrile in nine steps in an overall yield of 10%. Hydrolysis of ethyl 3-(2-phenylnaphthalen-1-yl)propanoate obtained from Suzuki–Miyaura coupling between the parent triflate and phenylboronic acid afforded the corresponding propionic acid which, after Friedel–Crafts acylation and bromine-mediated dehydrogenation, was subjected to Yang–Finnegan epoxidation to furnish 1. The preparation of analogs using this procedure is also discussed.