Aqueous Phosphoric Acid-Promoted [3.3]-Sigmatropic Rearrangement of 2-(Furan-3-yl)-2-(arylamino)acetonitrile

We report an aqueous phosphoric acid-promoted [3,3]-sigmatropic rearrangement of 2-(furan-3-yl)-2-(arylamino)acetonitriles for the regioselective synthesis of polysubstituted 2-arylfurans. This transition-metal-free method proceeds under mild, room-temperature conditions with broad functional-group tolerance. The utility of these products is showcased through their efficient one-step transformation into previously undescribed 5,6-dihydro-4H-benzo[ b ]furo[2,3- d ]azepine derivatives. This approach aligns with green chemistry principles and expands the synthetic utility of heteroaromatic rearrangements.