Synthetic applications of o- and p-halobenzyl sulfones as zwitterionic synthons: preparation of ortho-substituted cinnamates and biarylacetic acids

The synthetic applications of o-halobenzyl and p-halobenzyl sulfones as precursors of 1,3- and 1,5-zwitterionic synthons, respectively, are described. Their alpha-sulfonyl carbanions, generated by means of the phosphazene base P2-Et or BuLi or K2CO3 under PTC conditions, reacted with different electrophiles such as alkyl halides, aldehydes, and electrophilic olefins. Palladium-catalyzed cross-coupling processes such as Heck, Suzuki, and Sonogashira reactions can be efficiently performed at the halogen atom. These two sequential functionalization processes are applied to the synthesis of ortho-substituted cinnamates and pharmaceuticals belonging to the family of p-biarylacetic acids such as 4-biphenylacetic acid, namoxyrate, xenyhexenic acid, and biphenylpropionic acid.