Josiphos, copper complexes

A highly enantioselective reduction of o /3-unsaturated nitriles has been conducted by using a Cu(OAc)2-josiphos complex as the catalyst under hydrosilylation conditions. This reaction provides access to valuable /3-aryl-substituted chiral nitriles in good yields and with excellent enantioselectivities by employing a stable catalytic pre- cursor and a readily available commercial bisphosphine ligand. The active reducing species is believed to be copper hydride.315... 

High ees were achieved recently with Cu-JOSIPHOS complexes for the Michael addition of Grignard reagents to various substrates (302). Another ferrocene-based ligand, TANIAPHOS, was also efficient in the copper-catalyzed reductive addition of aldehydes and ketones to methyl acrylate (303). 

Copper hydride, generated in situ from CuCl(I), NaO( -Bu), and PMHS in combination with nonracemic, ferrocene-derived ligands, e.g., (i ,S)-JOSIPHOS, allowed reductions of prochiral a ,/3-unsaturated ketones with enantioselectivity up to 99% (259). JOSIPHOS and SEGPHOS complexed with copper hydride catalyze 1,4-hydrosilylation of a,y3-unsaturated lactones and esters into their corresponding esters with ee reaching 99% (260). 

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