title: Transmetalation from B to Rh in the course of the catalytic asymmetric 1,4-addition reaction of phenylboronic acid to enones: a computational comparison of diphosphane and diene ligands.
abstract: Transmetalation is a key elementary reaction of many important catalytic reactions. Among these, 1,4-addition of arylboronic acids to organic acceptors such as α,β-unsaturated ketones has emerged as one of the most important methods for asymmetric C-C bond formation. A key intermediate for the B-to-Rh transfer arising from quaternization on a boronic acid by a Rh-bound hydroxide (the active catalyst) has been proposed. Herein, DFT calculations (IEFPCM/PBE0/DGDZVP level of theory) establish the viability of this proposal, and characterize the associated pathways. The delivery of phenylboronic acid in the orientation suited for the B-to-Rh transfer from the very beginning is energetically preferable, and occurs with expulsion of Rh-coordinated water molecules. For the bulkier binap ligand, the barriers are higher (particularly for the phenylboronic acid activation step) due to a less favourable entropy term to the free energy, in accordance with the experimentally observed slower transmetalation rate.
authors.affiliation: School of Chemistry and Chemical Engineering, Hefei University of Technology, 193 Tunxi Road, Hefei 230009, China. liyg@hfut.edu.cn ekantchev@hfut.edu.cn ekantchev@gmail.com.
authors.forename: You-Gui
authors.initials: YG
authors.lastname: Li
authors.forename: Gang
authors.initials: G
authors.lastname: He
authors.forename: Hua-Li
authors.initials: HL
authors.lastname: Qin
authors.forename: Eric Assen B
authors.initials: EA
authors.lastname: Kantchev
mesh_terms: D000466:Alkadienes / Q000737:chemistry*; D001895:Boron / Q000737:chemistry; D001897:Boronic Acids / Q000737:chemistry*; D002384:Catalysis; D006878:Hydroxides / Q000737:chemistry; D007659:Ketones / Q000737:chemistry*; D008024:Ligands; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010720:Phosphines / Q000737:chemistry*; D011789:Quantum Theory; D012238:Rhodium / Q000737:chemistry
chemical_list: D000466:Alkadienes; D001897:Boronic Acids; D006878:Hydroxides; D007659:Ketones; D008024:Ligands; D009942:Organometallic Compounds; D010720:Phosphines; D012238:Rhodium; C044646:phosphine; D001895:Boron