Gold(I)-Catalyzed Intramolecular Hydroarylation of Phenol-Derived Propiolates and Certain Related Ethers as a Route to Selectively Functionalized Coumarins and 2<i>H</i>-Chromenes

Abstract

Methods are reported for the efficient assembly of a series of phenol-derived propiolates, including the parent system <b>56</b>, and their Au(I)-catalyzed cyclization (intramolecular hydroarylation) to give the corresponding coumarins (e.g., <b>1</b>). Simple syntheses of natural products such as ayapin (<b>144</b>) and scoparone (<b>145</b>) have been realized by such means, and the first of these subject to single-crystal X-ray analysis. A related process is described for the conversion of propargyl ethers such as <b>156</b> into the isomeric 2<i>H</i>-chromene precocene I (<b>159</b>), a naturally occurring inhibitor of juvenile hormone biosynthesis.