Ramesh Giri

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Name: Giri, Ramesh

Organization: The University of New Mexico , USA

Department: Department of Chemistry & Chemical Biology

Title: Assistant(PhD)

TOPICS

Inorganic Chemistry

Organic Chemistry

suzuki-miyaura Coupling

Chemicals
References

Ni-Catalyzed Regioselective 1,2-Dicarbofunctionalization of Olefins by Intercepting Heck Intermediates as Imine-Stabilized Transient Metallacycles

Co-reporter:Bijay Shrestha, Prakash Basnet, Roshan K. Dhungana, Shekhar KC, Surendra Thapa, Jeremiah M. Sears, and Ramesh Giri

Journal of the American Chemical Society August 9, 2017 Volume 139(Issue 31) pp:10653-10653

Publication Date(Web):July 24, 2017

DOI:10.1021/jacs.7b06340

We disclose a strategy for Ni-catalyzed dicarbofunctionalization of olefins in styrenes by intercepting Heck C(sp3)–NiX intermediates with arylzinc reagents. This approach utilizes a readily removable imine as a coordinating group that plays a dual role of intercepting oxidative addition species derived from aryl halides and triflates to promote Heck carbometalation and stabilizing the Heck C(sp3)–NiX intermediates as transient metallacycles to suppress β-hydride elimination and facilitate transmetalation/reductive elimination steps. This method affords diversely substituted 1,1,2-triarylethyl products that occur as structural motifs in various natural products.

Copper-Catalyzed Dicarbofunctionalization of Unactivated Olefins by Tandem Cyclization/Cross-Coupling

Co-reporter:Surendra Thapa, Prakash Basnet, and Ramesh Giri

Journal of the American Chemical Society April 26, 2017 Volume 139(Issue 16) pp:5700-5700

Publication Date(Web):April 12, 2017

DOI:10.1021/jacs.7b01922

We present a strategy that difunctionalizes unactivated olefins in 1,2-positions with two carbon-based entities. This method utilizes alkyl/arylzinc reagents derived from olefin-tethered alkyl/aryl halides that undergo radical cyclization to generate C(sp3)-Cu complexes in situ, which are intercepted with aryl and heteroaryl iodides. A variety of (arylmethyl)carbo- and heterocycles (N, O) can be synthesized with this new method.

General Copper-Catalyzed Coupling of Alkyl-, Aryl-, and Alkynylaluminum Reagents with Organohalides

Co-reporter:Bijay Shrestha, Surendra Thapa, Santosh K. Gurung, Ryan A. S. Pike, and Ramesh Giri

The Journal of Organic Chemistry 2016 Volume 81(Issue 3) pp:787-802

Publication Date(Web):January 6, 2016

DOI:10.1021/acs.joc.5b02077

We report the first example of a very general Cu-catalyzed cross-coupling of organoaluminum reagents with organohalides. The reactions proceed for the couplings of alkyl-, aryl-, and alkynylaluminum reagents with aryl and heteroaryl halides and vinyl bromides, affording the cross-coupled products in good to excellent yields. Both primary and secondary alkylaluminum reagents can be utilized as organometallic coupling partners. These reactions are not complicated by β-hydride elimination, and as a result rearranged products are not observed with secondary alkylaluminum reagents even for couplings with heteroaryl halides under “ligand-free” conditions. Radical clock experiment with a radical probe and relative reactivity study of Ph3Al with two haloarenes, 1-bromonaphthalene and 4-chlorobenzonitrile, having two different redox potentials indicates that the reaction does not involve free aryl radicals and radical anions as intermediates. These results combined with the result of the Hammett plot obtained by reacting Ph3Al with iodoarenes containing p-H, p-Me, p-F, and p-CF3 substituents, which shows a linear curve (R2 = 0.99) with a ρ value of +1.06, suggest that the current transformation follows an oxidative addition–reductive elimination pathway.

Copper-catalysed cross-coupling of arylzirconium reagents with aryl and heteroaryl iodides

Co-reporter:Surendra Thapa, Prakash Basnet, Santosh K. Gurung and Ramesh Giri

Chemical Communications 2015 vol. 51(Issue 19) pp:4009-4012

Publication Date(Web):30 Jan 2015

DOI:10.1039/C5CC00116A

An unprecedented CuI-catalysed cross-coupling of arylzirconium reagents with aryl and heteroaryl iodides is reported. Mechanistic studies with a Cp2ZrAr2 complex revealed that Cp2Zr(Ar)(Cl) is the reactive species that undergoes transmetalation with (PN-1)CuI. In addition, experiments with radical probes indicated that the reaction proceeds via a non-radical pathway.

Copper-catalysed cross-coupling: an untapped potential

Co-reporter:Surendra Thapa, Bijay Shrestha, Santosh K. Gurung and Ramesh Giri

Organic & Biomolecular Chemistry 2015 vol. 13(Issue 17) pp:4816-4827

Publication Date(Web):19 Mar 2015

DOI:10.1039/C5OB00200A

Copper is emerging as a viable catalytic metal for cross-coupling reactions to construct carbon–carbon (C–C) bonds. Recent revelations that Cu-catalysts can execute with high efficacy the cross-couplings of a variety of organometallic reagents, including organomagnesium, organoboron, organosilicon, organoindium and organomanganese, with alkyl, aryl and heteroaryl halides clearly demonstrate the versatility of Cu-based catalytic systems in conducting these reactions. In addition, Cu-catalysts are exhibiting a unique reactivity pattern that allows ligandless cross-coupling for aryl–heteroaryl and heteroaryl–heteroaryl bond formation, a transformation that generally requires special custom-designed ligands with Pd-catalysts. This review summarises early discoveries and subsequent advancements made in the area of Cu-catalysed cross-couplings of organometallic reagents with organohalides to form C–C bonds.

Ligand-Free Copper-Catalyzed Negishi Coupling of Alkyl-, Aryl-, and Alkynylzinc Reagents with Heteroaryl Iodides

Co-reporter:Surendra Thapa;Arjun Kafle;Dr. Santosh K. Gurung;Adam Montoya;Patrick Riedel ; Ramesh Giri

Angewandte Chemie 2015 Volume 127( Issue 28) pp:8354-8358

Publication Date(Web):

DOI:10.1002/ange.201502379

Abstract

Reported herein is an unprecedented ligand-free copper-catalyzed cross-coupling of alkyl-, aryl-, and alkynylzinc reagents with heteroaryl iodides. The reaction proceeds at room temperature for the coupling of primary, secondary, and tertiary alkylzinc reagents with heteroaryl iodides without rearrangement. An elevated temperature (100 °C) is required for aryl–heteroaryl and alkynyl–heteroaryl couplings.

Ligand-Free Copper-Catalyzed Negishi Coupling of Alkyl-, Aryl-, and Alkynylzinc Reagents with Heteroaryl Iodides

Co-reporter:Surendra Thapa;Arjun Kafle;Dr. Santosh K. Gurung;Adam Montoya;Patrick Riedel ; Ramesh Giri

Angewandte Chemie International Edition 2015 Volume 54( Issue 28) pp:8236-8240

Publication Date(Web):

DOI:10.1002/anie.201502379

Abstract

Copper-Catalyzed Suzuki–Miyaura Coupling of Arylboronate Esters: Transmetalation with (PN)CuF and Identification of Intermediates

Co-reporter:Santosh K. Gurung, Surendra Thapa, Arjun Kafle, Diane A. Dickie, and Ramesh Giri

Organic Letters 2014 Volume 16(Issue 4) pp:1264-1267

Publication Date(Web):February 5, 2014

DOI:10.1021/ol500310u

An efficient CuI-catalyzed Suzuki–Miyaura reaction was developed for the coupling of aryl- and heteroarylboronate esters with aryl and heteroaryl iodides at low catalyst loadings (2 mol %). The reaction proceeds under ligand-free conditions for aryl–heteroaryl and heteroaryl–heteroaryl couplings. We also conducted the first detailed mechanistic studies by synthesizing [(PN-2)CuI]2, [(PN-2)CuF]2, and (PN-2)CuPh (PN-2 = o-(di-tert-butylphosphino)-N,N-dimethylaniline) and demonstrated that [(PN-2)CuF]2 is the species that undergoes transmetalation with arylboronate esters.

Palladium-Catalysed, Directed CH Coupling with Organometallics

Co-reporter:Ramesh Giri;Surendra Thapa ;Arjun Kafle

Advanced Synthesis & Catalysis 2014 Volume 356( Issue 7) pp:1395-1411

Publication Date(Web):

DOI:10.1002/adsc.201400105

Copper-Catalyzed Coupling of Triaryl- and Trialkylindium Reagents with Aryl Iodides and Bromides through Consecutive Transmetalations

Co-reporter:Surendra Thapa;Dr. Santosh K. Gurung;Dr. Diane A. Dickie ;Dr. Ramesh Giri

Angewandte Chemie International Edition 2014 Volume 53( Issue 43) pp:11620-11624

Publication Date(Web):

DOI:10.1002/anie.201407586

Abstract

An efficient copper(I)-catalyzed coupling of triaryl and trialkylindium reagents with aryl iodides and bromides is reported. The reaction proceeds at low catalyst loadings (2 mol %) and generally only requires 0.33 equivalents of the triorganoindium reagent with respect to the aryl halide as all three organic nucleophilic moieties of the reagent are transferred to the products through consecutive transmetalations. The reaction tolerates a variety of functional groups and sterically hindered substrates. Furthermore, preliminary mechanistic studies that entailed the synthesis and characterization of potential reaction intermediates offered a glimpse of the elementary steps that constitute the catalytic cycle.

Copper-Catalyzed Coupling of Triaryl- and Trialkylindium Reagents with Aryl Iodides and Bromides through Consecutive Transmetalations

Co-reporter:Surendra Thapa;Dr. Santosh K. Gurung;Dr. Diane A. Dickie ;Dr. Ramesh Giri

Angewandte Chemie 2014 Volume 126( Issue 43) pp:11804-11808

Publication Date(Web):

DOI:10.1002/ange.201407586

Abstract

Copper-Catalyzed Hiyama Coupling of (Hetero)aryltriethoxysilanes with (Hetero)aryl Iodides

Co-reporter:Santosh K. Gurung, Surendra Thapa, Adarsh S. Vangala, and Ramesh Giri

Organic Letters 2013 Volume 15(Issue 20) pp:5378-5381

Publication Date(Web):September 30, 2013

DOI:10.1021/ol402701x

A CuI-catalyzed Hiyama coupling was achieved, which proceeds in the absence of an ancillary ligand for aryl–heteroaryl and heteroaryl–heteroaryl couplings. A P,N-ligand is required to obtain the best product yields for aryl–aryl couplings. In addition to facilitating transmetalation, CsF is also found to function as a stabilizer of the [CuAr] species, potentially generated as an intermediate after transmetalation of aryltriethoxysilanes with CuI-catalysts in the absence of ancillary ligands.

Copper-catalysed cross-coupling: an untapped potential

Co-reporter:Surendra Thapa, Bijay Shrestha, Santosh K. Gurung and Ramesh Giri

Organic & Biomolecular Chemistry 2015 - vol. 13(Issue 17) pp:NaN4827-4827

Publication Date(Web):2015/03/19

DOI:10.1039/C5OB00200A

Copper-catalysed cross-coupling of arylzirconium reagents with aryl and heteroaryl iodides

Co-reporter:Surendra Thapa, Prakash Basnet, Santosh K. Gurung and Ramesh Giri

Chemical Communications 2015 - vol. 51(Issue 19) pp:NaN4012-4012

Publication Date(Web):2015/01/30

DOI:10.1039/C5CC00116A

Copper-catalysed cross-couplings of arylboronate esters with aryl and heteroaryl iodides and bromides

Co-reporter:Santosh K. Gurung, Surendra Thapa, Bijay Shrestha and Ramesh Giri

Inorganic Chemistry Frontiers 2015 - vol. 2(Issue 6) pp:NaN653-653

Publication Date(Web):2015/02/16

DOI:10.1039/C4QO00331D

CuI-catalysed coupling of arylboronate esters with aryl and heteroaryl iodides and bromides is described. The transformation affords products in good yields using 5–10 mol% catalyst loadings. The described reaction requires a P,N-based bidentate ligand in combination with CuI for aryl–aryl coupling, but it proceeds without external ligands for aryl–heteroaryl coupling to afford the products. The reaction protocol can also be applied to achieve biarylation of diiodoarenes in reasonable yields.

The copper-catalysed Suzuki–Miyaura coupling of alkylboron reagents: disproportionation of anionic (alkyl)(alkoxy)borates to anionic dialkylborates prior to transmetalation

Co-reporter:Prakash Basnet, Surendra Thapa, Diane A. Dickie and Ramesh Giri

Chemical Communications 2016 - vol. 52(Issue 74) pp:NaN11075-11075

Publication Date(Web):2016/08/11

DOI:10.1039/C6CC05114F

We report the first example of CuI-catalysed coupling of alkylboron reagents with aryl and heteroaryl iodides that affords products in good to excellent yields. Preliminary mechanistic studies with alkylborates indicate that the anionic (alkoxy)(alkyl)borates, generated from alkyllithium and alkoxyboron reagents, undergo disproportionation to anionic dialkylborates and that both anionic alkylborates are active for transmetalation to a CuI-catalyst. Results from a radical clock experiment and the Hammett plot imply that the reaction likely proceeds via a non-radical pathway.