Volume 136, Issue 6 e202315005
Forschungsartikel

Reversal of Regioselectivity in Asymmetric C−H Bond Annulation with Bromoalkynes under Cobalt Catalysis**

Abir Das

Abir Das

Department of Chemistry, Indian Institution of Technology Kanpur, 208016 Kanpur, Uttar Pradesh, India

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Rajib Mandal

Rajib Mandal

Department of Chemistry, Indian Institution of Technology Kanpur, 208016 Kanpur, Uttar Pradesh, India

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Harihara Subramanian Ravi Sankar

Harihara Subramanian Ravi Sankar

Department of Chemistry, Indian Institution of Technology Kanpur, 208016 Kanpur, Uttar Pradesh, India

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Dr. Subramani Kumaran

Dr. Subramani Kumaran

Department of Chemistry, Indian Institution of Technology Kanpur, 208016 Kanpur, Uttar Pradesh, India

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Dr. J. Richard Premkumar

Dr. J. Richard Premkumar

PG & Research Department of Chemistry, Bishop Heber College, 620017 Tiruchirappalli, Tamil Nadu, India

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Dipanti Borah

Dipanti Borah

Department of Chemistry, Indian Institute of Technology Bombay, Powai, 400076 Mumbai, Maharashtra, India

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Prof. Dr. Basker Sundararaju

Corresponding Author

Prof. Dr. Basker Sundararaju

Department of Chemistry, Indian Institution of Technology Kanpur, 208016 Kanpur, Uttar Pradesh, India

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First published: 14 December 2023
Citations: 2
**

A previous version of this manuscript has been deposited on a preprint server (https://doi.org/10.26434/chemrxiv-2023-1rqz1).

Abstract

Metal-catalyzed asymmetric C−H bond annulation strategy offers a versatile platform, allowing the construction of complex P-chiral molecules through atom- and step-economical fashion. However, regioselective insertion of π-coupling partner between M−C bond with high enantio-induction remain elusive. Using commercially available Co(II) salt and chiral-Salox ligands, we demonstrate an unusual protocol for the regio-reversal, enantioselective C−H bond annulation of phosphinamide with bromoalkyne through desymmetrization. The reaction proceeds through ligand-assisted enantiodetermining cyclocobaltation followed by regioselective insertion of bromoalkyne between Co−C, subsequent reductive elimination, and halogen exchange with carboxylate resulted in P-stereogenic compounds in excellent ee (up to >99 %). The isolation of cobaltacycle involved in the catalytic cycle and the outcome of control experiments provide support for a plausible mechanism.

Conflict of interests

The authors declare no conflict of interest.

Data Availability Statement

The data that support the findings of this study are available in the supplementary material of this article.

The full text of this article hosted at iucr.org is unavailable due to technical difficulties.