Functionalized Biaryls By Organocatalysis

Biaryl compounds with a 1,1´ linkage are popular as ligands and catalysts for preparing chiral drug molecules. The 1,1´-biaryl structure also shows up in numerous natural products. But making this chemical motif isn’t trivial, particularly when the biaryls aren’t symmetrical. Syntheses usually require prefunctionalizaton or transition-metal catalysts. Chemists led by Rice University’s László Kürti have now developed an organocatalytic approach to making nonsymmetrical functionalized 1,1´-biaryls (Angew. Chem. Int. Ed. 2015, DOI: 10.1002/anie.201508419). The reaction weds a quinone monoacetal to a hydroxyaromatic compound with the help of an organic acid catalyst (example shown). The one-step reaction requires no metals and uses inexpensive starting materials. Kürti’s team reports it was able to scale up one example of the reaction to produce 26 g of the biaryl compound—a feat the chemists say shows the reaction is well-suited to syntheses of ligands and catalysts. The researchers believe the reaction’s mechanism most likely involves formation of a mixed acetal followed by a sigmatropic rearrangement. With this reaction chemists will be able to make many different kinds of nonsymmetrical functionalized 1,1´-biaryls, which they can use as catalysts or ligands for known or new reactions, Kürti tells C&EN.