Synthesis of Benzofurans and Dihydrobenzofurans from Phenols: Diastereoselective Benzylic C-H and Phenolic Site Annulation with Nsp3-ylides.

The synthesis of benzofurans and 2,3-dihydrobenzofuran-2-carbonitriles from phenols has been developed by a reaction of benzylic C-H and phenolic site annulation with nitrile-stabilized ammonium ylides. In this reaction, nitrile-stabilized Nsp3-ylides show reactivity behavior of acting as arylmethylene and arylmethylene-nitrile transferring synthons, in contrast to their well-known [1,2], [1,4], and [2,3]-sigmatropic rearrangements. The N-ylides were found to be more reactive than sulfoxonium and pyridinium ylides. This reaction provides diastereoselective construction of chiral centers and offers excellent substrate scope with varied electronic properties.