Mechanistic studies of the molybdenum-catalyzed asymmetric alkylation reaction
AUTOR(ES)
Hughes, David L.
FONTE
National Academy of Sciences
RESUMO
Enantiomerically enriched, deuterated branched carbonates (Z)-(S)-PhCH(OCO2Me)-CH = CHD (1-D), (Z)-(R)-PhCH(OCO2Me)CH = CHD (2-D), and linear carbonate (E)-(S)-PhCH = CHCHD(OCO2Me) (3-D) were used as probes in the Mo-catalyzed asymmetric allylic alkylation with sodium dimethyl malonate, catalyzed by ligand-complex 11 derived from the mixed benzamide/picolinamide of (S,S)-transdiaminocyclohexane and (norbornadiene)Mo(CO)4. The results of these studies, along with x-ray crystallography and solution NMR structural analysis of the π-allyl intermediate, conclusively established the reaction proceeded by a retention–retention pathway. This mechanism contrasts with that defined for Pd-catalyzed allylic alkylations, which proceed by an inversion–inversion pathway. A proposed rationale for the retention pathway for nucleophilic substitution involves CO-coordination to form a tri-CO intermediate, followed by complexation with the anion of dimethyl malonate to produce a seven-coordinate intermediate, which reductively eliminates to afford product with retention of configuration.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=397389Documentos Relacionados
- New mechanistic studies on the proline-catalyzed aldol reaction
- Chalcogen-containing oxazolines in the palladium-catalyzed asymmetric allylic alkylation
- Mechanistic studies on the catalytic cycle of rhodium-catalyzed asymmetric 1,4-addition of aryltitanate reagents to α,β-unsaturated ketones
- Rhodium-catalyzed asymmetric ring opening reactions of oxabicyclic alkenes: Catalyst and substrate studies leading to a mechanistic working model
- Asymmetric hetero-Diels–Alder reaction catalyzed by dirhodium(II) carboxamidates