Enantioselective oxy-Heck-Matsuda arylation in styrenic system: enantioselective synthesis of substituted trans-dihydrobenzofuram system and total synthesis of the neolignan (-)-conocarpan

The formation of C-C bonds in an enantioselective manner is of crucial importance in organic synthesis. In this regard, the enantioselective Heck¿Matsuda reaction is a very valuable synthetic tool. This arylation reaction has many advantages when compared to other Heck procedures, such as practicality, efficiency and speed. Recently, we developed a new method based on palladium catalysis for the preparation of trans-substituted dihydrobenzofurans in a diastereo and enantioselective way. Using the N,N-chiral ligand PyriBox we develop a method to promote the arylation of styrene using 2-hydroxylated aryldiazonium salt. The corresponding substituted 2,3-dihydrobenzofurans were obtained in yields up to 74% with excellent diastereoselectivity and good enantio control (up to 20:1 dr and 90:10 er). Our protocol was evaluated using diazonium salts containing EDG or EWG groups, several olefins with different substitution patterns. The absolute stereochemistry of the Heck¿Matsuda products were determined by X-ray and the total synthesis of natural product (-)-conocarpan (AU)