Shen, Zengming; Dornan, Peter K.; Khan, Hasan A.; Woo, Tom K.; Dong, Vy M. published the artcile< Mechanistic insights into the rhodium-catalyzed intramolecular ketone hydroacylation>, Reference of 112-63-0, the main research area is hydroacylation intramol cyclization ketoaldehyde benzodioxazepinone preparation rhodium catalyst; rhodium diphosphine catalyst asym hydroacylation ketoaldehyde chiral benzodioxazepinone preparation; kinetics hydroacylation mechanism ketoaldehyde rhodium diphosphine catalyzed lactone preparation; potential energy surface hydroacylation intramol ketoaldehyde rhodium diphosphine catalyst; benzodioxazepinone formation intramol hydroacylation ketoaldehyde potential energy surface; optimized geometry rhodium acyl hydro diphosphine complex hydroacylation intermediate.
Rhodium diphosphine catalysts, [Rh(dppp)2]BF4 and [Rh((R)-DTBM-SEGPHOS)]BF4 [dppp = 1,3-bis(diphenylphosphino)propane, DTBM-SEGPHOS = (4R)-[4,4′-bi-1,3-benzodioxole]-5,5′-bis(diarylphosphine), aryl = 3,5-di-tert-butyl-4-methoxyphenyl] exhibit high catalytic activity, chemo- and enantioselectivity in intramol. ketone group hydroacylation of oxo-substituted salicylaldehyde ethers, 2-RCOCHR1OC6H4CHO (1a-o), yielding 3-R-2,3-dihydro-1,4-benzodioxepin-5-ones I (2a-o; R1 = H, R = Ph, 4-CF3C6H4, 4-MeO2CC6H4, 4-ClC6H4, 4-FC6H4, 4-MeC6H4, 4-MeOC6H4, 2-naphthyl, Bu, iPr, tBu, PhCH2, Me, 2-furyl, 2-thienyl; rac-2p, R1 = R = Me; rac-2q, R1 = R = Ph). The reaction catalyzed by [Rh((R)-DTBM-SEGPHOS)]BF4 afforded seven-membered lactones 2a-o in large enantiomeric excess. A combined exptl. and theor. study aimed to elucidate the mechanism and origin of selectivity in this C-H bond activation process, is presented. Evidence is presented for a mechanistic pathway involving three key steps: (1) rhodium(I) oxidative addition into the aldehyde C-H bond, (2) insertion of the ketone C:O double bond into the rhodium hydride, and (3) C-O bond-forming reductive elimination. Kinetic isotope effects and Hammett plots support that ketone insertion is the turnover-limiting step. Detailed kinetic experiments were performed using both dppp and (R)-DTBM-SEGPHOS as ligands. With dppp, the keto-aldehyde substrate assists in dissociating a dimeric precatalyst [Rh2(μ-η6:κP,κP’-dppp)2][BF4]2 (8) and binds an active monomeric form of the catalyst. With [Rh((R)-DTBM-SEGPHOS)]BF4, there is no induction period and both substrate and product inhibition are observed In addition, competitive decarbonylation produces a catalytically inactive rhodium carbonyl species that accumulates over the course of the reaction. Both mechanisms were modeled with a kinetics simulation program, and the models were consistent with the exptl. data. D. functional theory calculations were performed to understand more elusive details of this transformation. These simulations support that the ketone insertion step has the highest energy transition state and reveal an unexpected interaction between the carbonyl-oxygen lone pair and a Rh d-orbital in this transition state structure. Finally, a model based on the calculated transition-state geometry is proposed to rationalize the absolute sense of enantioinduction observed using (R)-DTBM-SEGPHOS as the chiral ligand.
Journal of the American Chemical Society published new progress about Acyl groups (rhodium acyl complexes). 112-63-0 belongs to class esters-buliding-blocks, and the molecular formula is C19H34O2, Reference of 112-63-0.
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