Congested C-C bonds by Pd-catalyzed enantioselective allyl-allyl cross-coupling, a mechanism-guided solution.
Under the influence of a chiral bidentate diphosphine ligand, the Pd-catalyzed asymmetric cross-coupling of allylboron reagents and allylic electrophiles establishes 1,5-dienes with adjacent stereocenters in high regio- and stereoselectivity. A mechanistic study of the coupling utilizing reaction calorimetry and density functional theory analysis suggests that the reaction operates through an inner-sphere 3,3'-reductive elimination pathway, which is both rate-defining and stereodefining. Coupled with optimized reaction conditions, this mechanistic detail is used to expand the scope of allyl-allyl couplings to allow the generation of 1,5-dienes with tertiary centers adjacent to quaternary centers as well as a unique set of cyclic structures.
Department of Chemistry, Merkert Chemistry Center, Boston College , Chestnut Hill, Massachusetts 02467, United States.
Michael J
MJ
Ardolino
James P
JP
Morken
D000466:Alkadienes / Q000138:chemical synthesis* / Q000737:chemistry; D000498:Allyl Compounds / Q000737:chemistry*; D001896:Boron Compounds / Q000737:chemistry*; D002384:Catalysis; D008024:Ligands; D008958:Models, Molecular; D010165:Palladium / Q000737:chemistry*; D010720:Phosphines / Q000737:chemistry; D013237:Stereoisomerism
D000466:Alkadienes; D000498:Allyl Compounds; D001896:Boron Compounds; D008024:Ligands; D010720:Phosphines; D010165:Palladium; C044646:phosphine