Mechanism and Selectivity of Ru(II) - and Rh(III) -Catalyzed Oxidative Spiroannulation of Naphthols and Phenols with Alkynes through a C-H Activation/Dearomatization Strategy.
Chemistry. 2016 Jun 27; 22(27):9356-65.C

Abstract

The ruthenium- and rhodium-catalyzed oxidative spiroannulation of naphthols and phenols with alkynes was investigated by means of density functional theory calculations. The results show that the reaction undergoes O-H deprotonation/C(sp(2))-H bond cleavage through a concerted metalation-deprotonation mechanism/migratory insertion of the alkyne into the M-C bond to deliver the eight-membered metallacycle. However, the dearomatization through the originally proposed enol-keto tautomerization/C-C reductive elimination was calculated to be kinetically inaccessible. Alternatively, an unusual metallacyclopropene, generated from the isomerization of the eight-membered metallacycle through rotation of the C-C double bond, was identified as a key intermediate to account for the experimental results. The subsequent C-C coupling between the carbene carbon atom and the carbon atom of the 2-naphthol/phenol ring was calculated to be relatively facile, leading to the formation of the unexpected dearomatized products. The calculations reproduce quite well the experimentally observed formal [5+2] cycloaddition in the rhodium-catalyzed oxidative annulation of 2-vinylphenols with alkynes. The calculations show that compared with the case of 2-alkenylphenols, the presence of conjugation effects and less steric repulsion between the phenol ring and the vinyl moiety make the competing reductive oxyl migration become dominant, which enables the selectivity switch from the spiroannulation to the formal [5+2] cycloaddition.

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Authors+Show Affiliations

Zhang M

Department of Chemistry, School of Science, Tianjin University, Tianjin, 300072, P.R. China.

Huang G

Department of Chemistry, School of Science, Tianjin University, Tianjin, 300072, P.R. China. gphuang@tju.edu.cn. Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin, 300072, P.R. China. gphuang@tju.edu.cn.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

27225930

Citation

Zhang, Mei, and Genping Huang. "Mechanism and Selectivity of Ru(II) - and Rh(III) -Catalyzed Oxidative Spiroannulation of Naphthols and Phenols With Alkynes Through a C-H Activation/Dearomatization Strategy." Chemistry (Weinheim an Der Bergstrasse, Germany), vol. 22, no. 27, 2016, pp. 9356-65.

Zhang M, Huang G. Mechanism and Selectivity of Ru(II) - and Rh(III) -Catalyzed Oxidative Spiroannulation of Naphthols and Phenols with Alkynes through a C-H Activation/Dearomatization Strategy. Chemistry. 2016;22(27):9356-65.

Zhang, M., & Huang, G. (2016). Mechanism and Selectivity of Ru(II) - and Rh(III) -Catalyzed Oxidative Spiroannulation of Naphthols and Phenols with Alkynes through a C-H Activation/Dearomatization Strategy. Chemistry (Weinheim an Der Bergstrasse, Germany), 22(27), 9356-65. https://doi.org/10.1002/chem.201600884

Zhang M, Huang G. Mechanism and Selectivity of Ru(II) - and Rh(III) -Catalyzed Oxidative Spiroannulation of Naphthols and Phenols With Alkynes Through a C-H Activation/Dearomatization Strategy. Chemistry. 2016 Jun 27;22(27):9356-65. PubMed PMID: 27225930.

* Article titles in AMA citation format should be in sentence-case

TY - JOUR T1 - Mechanism and Selectivity of Ru(II) - and Rh(III) -Catalyzed Oxidative Spiroannulation of Naphthols and Phenols with Alkynes through a C-H Activation/Dearomatization Strategy. AU - Zhang,Mei, AU - Huang,Genping, Y1 - 2016/05/25/ PY - 2016/02/24/received PY - 2016/5/27/entrez PY - 2016/5/27/pubmed PY - 2016/5/27/medline KW - density functional calculations KW - metallacyclopropene KW - oxidative spiroannulation KW - reaction mechanisms KW - selectivity SP - 9356 EP - 65 JF - Chemistry (Weinheim an der Bergstrasse, Germany) JO - Chemistry VL - 22 IS - 27 N2 - The ruthenium- and rhodium-catalyzed oxidative spiroannulation of naphthols and phenols with alkynes was investigated by means of density functional theory calculations. The results show that the reaction undergoes O-H deprotonation/C(sp(2))-H bond cleavage through a concerted metalation-deprotonation mechanism/migratory insertion of the alkyne into the M-C bond to deliver the eight-membered metallacycle. However, the dearomatization through the originally proposed enol-keto tautomerization/C-C reductive elimination was calculated to be kinetically inaccessible. Alternatively, an unusual metallacyclopropene, generated from the isomerization of the eight-membered metallacycle through rotation of the C-C double bond, was identified as a key intermediate to account for the experimental results. The subsequent C-C coupling between the carbene carbon atom and the carbon atom of the 2-naphthol/phenol ring was calculated to be relatively facile, leading to the formation of the unexpected dearomatized products. The calculations reproduce quite well the experimentally observed formal [5+2] cycloaddition in the rhodium-catalyzed oxidative annulation of 2-vinylphenols with alkynes. The calculations show that compared with the case of 2-alkenylphenols, the presence of conjugation effects and less steric repulsion between the phenol ring and the vinyl moiety make the competing reductive oxyl migration become dominant, which enables the selectivity switch from the spiroannulation to the formal [5+2] cycloaddition. SN - 1521-3765 UR - https://www.unboundmedicine.com/medline/citation/27225930/Mechanism_and_Selectivity_of_Ru_II____and_Rh_III___Catalyzed_Oxidative_Spiroannulation_of_Naphthols_and_Phenols_with_Alkynes_through_a_C_H_Activation/Dearomatization_Strategy_ DB - PRIME DP - Unbound Medicine ER -

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Mechanism and Selectivity of Ru(II) - and Rh(III) -Catalyzed Oxidative Spiroannulation of Naphthols and Phenols with Alkynes through a C-H Activation/Dearomatization Strategy.Chemistry. 2016 Jun 27; 22(27):9356-65.C