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Article: Mechanism and Enantioselectivity of Dirhodium-Catalyzed Intramolecular C–H Amination of Sulfamate

TitleMechanism and Enantioselectivity of Dirhodium-Catalyzed Intramolecular C–H Amination of Sulfamate
Authors
Issue Date2013
Citation
The Journal of Organic Chemistry, 2013, v. 78, p. 12460-12468 How to Cite?
AbstractThe mechanisms and enantioselectivities of the dirhodium (Rh2L4, L = formate, N-methylformamide, S-nap)-catalyzed intramolecular C–H aminations of 3-phenylpropylsulfamate ester have been investigated in detail with BPW91 density functional theory computations. The reactions catalyzed by the Rh2II,II catalysts start from the oxidation of the Rh2II,II dimer to a triplet mixed-valent Rh2II,III–nitrene radical, which should facilitate radical H-atom abstraction. However, in the Rh2(formate)4-promoted reaction, as a result of a minimum-energy crossing point (MECP) between the singlet and triplet profiles, a direct C–H bond insertion is postulated. The Rh2(N-methylformamide)4 reaction exhibits quite different mechanistic characteristics, taking place via a two-step process involving (i) intramolecular H-abstraction on the triplet profile to generate a diradical intermediate and (ii) C–N formation by intersystem crossing from the triplet state to the open-shell singlet state. The stepwise mechanism was found to hold also in the reaction of 3-phenylpropylsulfamate ester catalyzed by Rh2(S-nap)4. Furthermore, the diradical intermediate also constitutes the starting point for competition steps involving enantioselectivity, which is determined by the C–N formation open-shell singlet transition state. This mechanistic proposal is supported by the calculated enantiomeric excess (94.2% ee) with the absolute stereochemistry of the product as R, in good agreement with the experimental results (92.0% ee).
Persistent Identifierhttp://hdl.handle.net/10722/202567
ISI Accession Number ID

 

DC FieldValueLanguage
dc.contributor.authorZhang, Xen_US
dc.contributor.authorKe, Zen_US
dc.contributor.authorDeYonker, Nen_US
dc.contributor.authorXu, Hen_US
dc.contributor.authorLi, Zen_US
dc.contributor.authorXu, Xen_US
dc.contributor.authorZhang, Xen_US
dc.contributor.authorSu, C-Yen_US
dc.contributor.authorPhillips, DLen_US
dc.contributor.authorZhao, Cen_US
dc.date.accessioned2014-09-19T08:41:16Z-
dc.date.available2014-09-19T08:41:16Z-
dc.date.issued2013en_US
dc.identifier.citationThe Journal of Organic Chemistry, 2013, v. 78, p. 12460-12468en_US
dc.identifier.urihttp://hdl.handle.net/10722/202567-
dc.description.abstractThe mechanisms and enantioselectivities of the dirhodium (Rh2L4, L = formate, N-methylformamide, S-nap)-catalyzed intramolecular C–H aminations of 3-phenylpropylsulfamate ester have been investigated in detail with BPW91 density functional theory computations. The reactions catalyzed by the Rh2II,II catalysts start from the oxidation of the Rh2II,II dimer to a triplet mixed-valent Rh2II,III–nitrene radical, which should facilitate radical H-atom abstraction. However, in the Rh2(formate)4-promoted reaction, as a result of a minimum-energy crossing point (MECP) between the singlet and triplet profiles, a direct C–H bond insertion is postulated. The Rh2(N-methylformamide)4 reaction exhibits quite different mechanistic characteristics, taking place via a two-step process involving (i) intramolecular H-abstraction on the triplet profile to generate a diradical intermediate and (ii) C–N formation by intersystem crossing from the triplet state to the open-shell singlet state. The stepwise mechanism was found to hold also in the reaction of 3-phenylpropylsulfamate ester catalyzed by Rh2(S-nap)4. Furthermore, the diradical intermediate also constitutes the starting point for competition steps involving enantioselectivity, which is determined by the C–N formation open-shell singlet transition state. This mechanistic proposal is supported by the calculated enantiomeric excess (94.2% ee) with the absolute stereochemistry of the product as R, in good agreement with the experimental results (92.0% ee).en_US
dc.languageengen_US
dc.relation.ispartofThe Journal of Organic Chemistryen_US
dc.titleMechanism and Enantioselectivity of Dirhodium-Catalyzed Intramolecular C–H Amination of Sulfamateen_US
dc.typeArticleen_US
dc.identifier.emailPhillips, DL: phillips@hku.hken_US
dc.identifier.authorityPhillips, DL=rp00770en_US
dc.identifier.doi10.1021/jo402101hen_US
dc.identifier.pmid24308708-
dc.identifier.hkuros237014en_US
dc.identifier.volume78en_US
dc.identifier.spage12460en_US
dc.identifier.epage12468en_US
dc.identifier.isiWOS:000329077900016-

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