An efficient tandem reaction approach has been developed to prepare 4-chromanones from electron-rich phenols and 3,3-dimethylacrylic acid or crotonic acid in boiling toluene using 20 mol % bismuth(III) triflate as the catalyst.  The reaction was also successful from the corresponding aryl esters of these acids under the same conditions.  The procedure was convenient to perform, and 25-90% yields of products were realized following purification.  A set of substrates (14 for each acid) was reacted to help define the scope of the process.  Additional experiments were performed, which confirmed that the sequence of events involved (1) esterification of the acid by the phenol, (2) Fries rearrangement of the 2-butenyl acylium fragment to the less hindered ortho position and (3) oxa-Michael ring closure of the phenolic OH to the side chain enone of the Fries product.  This poster will illustrate our results and outline a plausible mechanism for the process.<br/>

Bismuth(III) triflate catalyzed tandem esterification–Fries–oxa-Michael route to 4-chromanones

253rd National Meeting (2017)

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