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Rh-catalyzed intermolecular reactions of cyclic α-diazocarbonyl compounds with selectivity over tertiary C-H bond migration.
J Am Chem Soc. 2012 Jul 04; 134(26):11035-43.JA

Abstract

Intermolecular Rh-catalyzed reactions of cyclic α-diazocarbonyl compounds with chemoselectivity over β-hydride elimination are described. These methods represent the first general intermolecular reactions of Rh-carbenoids that are selective over tertiary β-C-H bond migration. Successful transformations include cyclopropanation, cyclopropenation, and various X-H insertion reactions with a broad scope of substrates. We propose that the intermolecular approach of substrates to carbenes from acyclic diazo precursors may be relatively slow due to a steric interaction with the ester function, which is perpendicular to the π-system of the carbene. For carbenes derived from five- and six-membered cyclic α-diazocarbonyls, it is proposed that the carbene is constrained to be more conjugated with the carbonyl, thereby relieving the steric interaction for intermolecular reactions, and accelerating the rate of intermolecular reactivity relative to intramolecular β-hydride migration. However, attempts to use α-diazo-β-ethylcaprolactone in intermolecular cyclopropanation with styrene were unsuccessful. It is proposed that the conformational flexibility of the seven-membered ring allows the carbonyl to be oriented perpendicular to Rh-carbene. The significant intermolecular interaction between the carbonyl and approaching substrate is in agreement with the poor ability of α-diazo-β-ethylcaprolactone to participate in intermolecular cyclopropanation reactions. DFT calculations provide support for the mechanistic proposals that are described.

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Authors+Show Affiliations

DeAngelis A
Brown Laboratories, Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA.
Dmitrenko O
No affiliation info available
Fox JM
No affiliation info available

MeSH

Azo CompoundsCatalysisComputer SimulationCyclopropanesHydrogenMethaneMolecular ConformationRhodiumStereoisomerism

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural
Research Support, U.S. Gov't, Non-P.H.S.

Language

eng

PubMed ID

22676258

Citation

DeAngelis, Andrew, et al. "Rh-catalyzed Intermolecular Reactions of Cyclic Α-diazocarbonyl Compounds With Selectivity Over Tertiary C-H Bond Migration." Journal of the American Chemical Society, vol. 134, no. 26, 2012, pp. 11035-43.
DeAngelis A, Dmitrenko O, Fox JM. Rh-catalyzed intermolecular reactions of cyclic α-diazocarbonyl compounds with selectivity over tertiary C-H bond migration. J Am Chem Soc. 2012;134(26):11035-43.
DeAngelis, A., Dmitrenko, O., & Fox, J. M. (2012). Rh-catalyzed intermolecular reactions of cyclic α-diazocarbonyl compounds with selectivity over tertiary C-H bond migration. Journal of the American Chemical Society, 134(26), 11035-43. https://doi.org/10.1021/ja3046712
DeAngelis A, Dmitrenko O, Fox JM. Rh-catalyzed Intermolecular Reactions of Cyclic Α-diazocarbonyl Compounds With Selectivity Over Tertiary C-H Bond Migration. J Am Chem Soc. 2012 Jul 4;134(26):11035-43. PubMed PMID: 22676258.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Rh-catalyzed intermolecular reactions of cyclic α-diazocarbonyl compounds with selectivity over tertiary C-H bond migration. AU - DeAngelis,Andrew, AU - Dmitrenko,Olga, AU - Fox,Joseph M, Y1 - 2012/06/19/ PY - 2012/6/9/entrez PY - 2012/6/9/pubmed PY - 2012/10/12/medline SP - 11035 EP - 43 JF - Journal of the American Chemical Society JO - J Am Chem Soc VL - 134 IS - 26 N2 - Intermolecular Rh-catalyzed reactions of cyclic α-diazocarbonyl compounds with chemoselectivity over β-hydride elimination are described. These methods represent the first general intermolecular reactions of Rh-carbenoids that are selective over tertiary β-C-H bond migration. Successful transformations include cyclopropanation, cyclopropenation, and various X-H insertion reactions with a broad scope of substrates. We propose that the intermolecular approach of substrates to carbenes from acyclic diazo precursors may be relatively slow due to a steric interaction with the ester function, which is perpendicular to the π-system of the carbene. For carbenes derived from five- and six-membered cyclic α-diazocarbonyls, it is proposed that the carbene is constrained to be more conjugated with the carbonyl, thereby relieving the steric interaction for intermolecular reactions, and accelerating the rate of intermolecular reactivity relative to intramolecular β-hydride migration. However, attempts to use α-diazo-β-ethylcaprolactone in intermolecular cyclopropanation with styrene were unsuccessful. It is proposed that the conformational flexibility of the seven-membered ring allows the carbonyl to be oriented perpendicular to Rh-carbene. The significant intermolecular interaction between the carbonyl and approaching substrate is in agreement with the poor ability of α-diazo-β-ethylcaprolactone to participate in intermolecular cyclopropanation reactions. DFT calculations provide support for the mechanistic proposals that are described. SN - 1520-5126 UR - https://www.unboundmedicine.com/medline/citation/22676258/Rh_catalyzed_intermolecular_reactions_of_cyclic_α_diazocarbonyl_compounds_with_selectivity_over_tertiary_C_H_bond_migration_ L2 - https://doi.org/10.1021/ja3046712 DB - PRIME DP - Unbound Medicine ER -