Palladium-Catalyzed Remote ortho-C-H Alkenylation of Alkyl Aryl Sulfones: Access to Densely Functionalized Indane Derivatives

Abstract

A practical method for the palladium-cat-alyzed ortho-olefination of benzyl and phenethyl 2-pyridyl sulfones with electron-deficient alkenes using N-fluoro-2,4,6-trimethylpyridinium triflate ([F+]) as the terminal oxidant is described. The che-lating auxiliary (2-pyridyl)sulfonyl unit was demon-strated to be the key to the success of this reaction, which occurs efficiently with excellent regioselectiv-ity and monosubstitution selectivity. A variety of steric and electronic changes to both coupling part-ners is tolerated, including substitution at the ben-zylic position of the sulfone compound. Further-more, no appreciable loss of enantiopurity is ob-served when using non-racemic substrates. This method provides access to indane derivatives hold-ing three contiguous stereogenic centers with high diastereocontrol. The indane framework was con-structed by intramolecular Michael addition of the a-sulfonyl carbanion to the electrophilic alkene