A novel and convenient mercury(II) mediated synthesis of chroman-4-ones

Six-Membered Ring Systems: With O and/or S Atoms

Abstract: The review covers work published in the calendar year 2010. Novel reaction chemistry and new ring synthetic methods for pyrans, [1]benzopyrans, dihydro[1]benzopyrans (chromenes, chromans), [2]benzopyrans, dihydro[2]benzopyrans (isochromenes, isochromans), pyranones, coumarins, chromones, xanthenes, xanthones, thiopyrans, dioxins. dioxanes, trioxanes, tetraoxanes, dithianes, trithianes, oxathianes are reviewed.

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

Abstract: An efficient tandem reaction approach is described to prepare 4-chromanones from electron-rich phenols and 3,3-dimethylacrylic acid or trans -crotonic acid in boiling toluene using 20 mol % bismuth(III) triflate as the catalyst. The reaction is also successful from the corresponding aryl esters of each of these acids under the same conditions. The procedure is convenient to perform, and 25–90% yields of products are realized following chromatography. A range of substrates is included (14 substrates for each acid) to help define the scope of the process. Additional experiments are reported, which confirm that the sequence of events involves (1) esterification, (2) Fries rearrangement and (3) oxa-Michael ring closure.

A Novel and Convenient Mercury(II) Mediated Synthesis of Chroman-4-ones.

Abstract: A simple route to chroman-4-ones from γ-bromopropynyl aryl ethers (1) using mercury(II) trifluoroacetate as a catalyst is described.