Stereospecific Cross-Coupling Of Chiral Alcohols With Organoboronic Acids

Boronic acids are widely employed in the cross-coupling reaction due to their ready accessibility, stability, and good reactivity. The cross-coupling of boronic acids with allylic electrophiles constitutes a powerful approach for the formation of carbon-carbon bonds by introducing the allyl moiety to target compounds, which allows various transformations such as oxidation, reduction, and addition.Although allylic halides and alcohol derivatives, such as allylic esters, carbonates, and phosphates have been identified as useful allylic electrophiles with various reactivity and selectivity in their cross-coupling reactions with boronic acids, stereoselective cross-coupling of chiral alcohols with boric acid was rare explored. The synthetic routes for the preparation of allylic alcohols, including optically active ones are in general shorter than that for the corresponding halides and alcohol derivatives. The cross-coupling of chiral allylic alcohols with boronic acids will be an attractive complement to stereospecific allylic alkylation.A series of studies indicated that allylic alcohol can serve as an efficient allylic electrophile and the stereoselective transformation can also be realized under suitable conditions。Therefore allylic alcohols can be efficient reagents for stereospecific cross-coupling with boronic acids.Stereospecific cross-coupling of chiral allylic alcohols with boronic acids has been developed and provides a powerful approach to obtain optically active alkenes. No additional activating reagent was needed for the reaction system. Easy accessibility and atom-economy of chiral alcohols made it a useful way to introduce allyl moiety to target compounds. The excellent tolerance of the reaction to a variety of functional groups was also observed. To study the mechanism, the reactive intermediates have been detected from the reaction system by high resolution mass spectrometer. The studies suggested that the cross-coupling was realized via carbon-oxygen bond cleavage and generation of palladium π-complex.