Synthesis of heteroarylated ketones via bismuth(III) triflate-promoted regioselective 1,4-and 1,6-additions of electron-rich heteroarenes to cyclic enones and dienones

The development and optimization of bismuth(III) triflate-promoted regioselective 1,4- and 1,6-additions of electron-rich heteroarenes to cyclic, beta,beta-disubstituted enones and dienones is described. Additions of a range of heteroarenes, including furan, thiophene, pyrrole, and indole nucleophiles, to cyclic, beta,beta-disubstituted enones occur to form all-carbon quaternary centers in up to 88% yield. In addition, regioselective 1,6-additions of electron-rich heteroarenes to 3-vinyl-2-cyclohexenone occur to produce a variety of delta-heteroarylated, beta,beta-disubstituted enones in up to 93% yield. The high 1,6-selectivity for these reactions is attributed to the increased steric bulk at the delta-position relative to the delta-position, and no competing 1,4-conjugate addition is observed. (C) 2018 Published by Elsevier Ltd.