Access to Substituted Propenoic Acids via Rh(III)-Catalyzed C–H Allylation of (Hetero)Arenes with Methyleneoxetanones

An efficient synthesis of disubstituted acrylic acids has been realized via Rh­(III)-catalyzed C–H activation of (hetero)­arenes and coupling with four-membered methyleneoxetanones under redox-neutral conditions. In most cases, the reactions are silver-free, and the products are exclusively E-selective with a broad substrate scope. The transformation proceeds via ortho C–H activation followed by selective olefin insertion and β-oxygen elimination.