Palladium complexes of the N-fused heterocycle derived abnormal N-heterocyclic carbenes for the much-preferred Cu-free and the amine-free Sonogashira coupling in air

Alex John; Sudipta Modak; Mahesh Madasu; Madanakrishna Katari; Prasenjit Ghosh

doi:10.1016/j.poly.2013.01.062

Palladium complexes of the N-fused heterocycle derived abnormal N-heterocyclic carbenes for the much-preferred Cu-free and the amine-free Sonogashira coupling in air

Alex John, Sudipta Modak, Mahesh Madasu, Madanakrishna Katari, Prasenjit Ghosh

Chemistry (Twin Cities)

Research output: Contribution to journal › Article › peer-review

46 Scopus citations

Abstract

Abnormal N-heterocyclic carbenes of the N-fused heterocycles were employed in stabilizing a series of PEPPSI (Pyridine Enhanced Precatalyst Preparation Stabilization and Initiation) themed complexes of the type (abnormal-NHC) PdI₂(pyridine). Specifically, imidazo[1,2-a]pyridine based abnormal complexes, trans-{(1-ethyl-2-(4-R-phenyl)-imidazol-3-ylidene[1,2-a]pyridine)} PdI₂(pyridine) [R = F (1b), Cl (2b), Br (3b) and Me (4b)] were synthesized from the reaction of corresponding imidazo[1,2-a]pyridinium iodide salts (1-4)a with PdCl₂ in pyridine in the presence of K ₂CO₃ as a base. The (1-4)b complexes carried out the Sonogashira couplings of the aryl bromide and iodide substrates with terminal alkynes in a mixed aqueous medium in air under the Cu-free and amine-free conditions. The density functional theory studies revealed that in the (1-4)b complexes, the C_carbene-Pd σ-bonding interaction was significantly stronger than the trans Pd-N_pyridine σ-bonding interaction.

Original language	English (US)
Pages (from-to)	20-29
Number of pages	10
Journal	Polyhedron
Volume	64
DOIs	https://doi.org/10.1016/j.poly.2013.01.062
State	Published - 2013

Bibliographical note

Funding Information:
We thank Department of Science and Technology (Grant No: SR/S1/IC-15/2011 ), New Delhi, for financial support of this research. We are grateful to the National Single Crystal X-ray Diffraction Facility and Sophisticated Analytical Instrument Facility at IIT Bombay, India, for the crystallographic and other characterization data. Computational facilities from the IIT Bombay Computer Center are gratefully acknowledged. S.M. thanks CSIR, New Delhi and M.K. thanks BRNS, Mumbai for research fellowship.

Keywords

Abnormal N-heterocyclic carbene (NHC)
Amine-free
Cu-free
DFT studies
Palladium
Sonogashira reaction

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10.1016/j.poly.2013.01.062

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title = "Palladium complexes of the N-fused heterocycle derived abnormal N-heterocyclic carbenes for the much-preferred Cu-free and the amine-free Sonogashira coupling in air",

abstract = "Abnormal N-heterocyclic carbenes of the N-fused heterocycles were employed in stabilizing a series of PEPPSI (Pyridine Enhanced Precatalyst Preparation Stabilization and Initiation) themed complexes of the type (abnormal-NHC) PdI2(pyridine). Specifically, imidazo[1,2-a]pyridine based abnormal complexes, trans-{(1-ethyl-2-(4-R-phenyl)-imidazol-3-ylidene[1,2-a]pyridine)} PdI2(pyridine) [R = F (1b), Cl (2b), Br (3b) and Me (4b)] were synthesized from the reaction of corresponding imidazo[1,2-a]pyridinium iodide salts (1-4)a with PdCl2 in pyridine in the presence of K 2CO3 as a base. The (1-4)b complexes carried out the Sonogashira couplings of the aryl bromide and iodide substrates with terminal alkynes in a mixed aqueous medium in air under the Cu-free and amine-free conditions. The density functional theory studies revealed that in the (1-4)b complexes, the Ccarbene-Pd σ-bonding interaction was significantly stronger than the trans Pd-Npyridine σ-bonding interaction.",

keywords = "Abnormal N-heterocyclic carbene (NHC), Amine-free, Cu-free, DFT studies, Palladium, Sonogashira reaction",

author = "Alex John and Sudipta Modak and Mahesh Madasu and Madanakrishna Katari and Prasenjit Ghosh",

note = "Funding Information: We thank Department of Science and Technology (Grant No: SR/S1/IC-15/2011 ), New Delhi, for financial support of this research. We are grateful to the National Single Crystal X-ray Diffraction Facility and Sophisticated Analytical Instrument Facility at IIT Bombay, India, for the crystallographic and other characterization data. Computational facilities from the IIT Bombay Computer Center are gratefully acknowledged. S.M. thanks CSIR, New Delhi and M.K. thanks BRNS, Mumbai for research fellowship. ",

year = "2013",

doi = "10.1016/j.poly.2013.01.062",

language = "English (US)",

volume = "64",

pages = "20--29",

journal = "Polyhedron",

issn = "0277-5387",

publisher = "Elsevier Ltd",

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TY - JOUR

T1 - Palladium complexes of the N-fused heterocycle derived abnormal N-heterocyclic carbenes for the much-preferred Cu-free and the amine-free Sonogashira coupling in air

AU - John, Alex

AU - Modak, Sudipta

AU - Madasu, Mahesh

AU - Katari, Madanakrishna

AU - Ghosh, Prasenjit

N1 - Funding Information: We thank Department of Science and Technology (Grant No: SR/S1/IC-15/2011 ), New Delhi, for financial support of this research. We are grateful to the National Single Crystal X-ray Diffraction Facility and Sophisticated Analytical Instrument Facility at IIT Bombay, India, for the crystallographic and other characterization data. Computational facilities from the IIT Bombay Computer Center are gratefully acknowledged. S.M. thanks CSIR, New Delhi and M.K. thanks BRNS, Mumbai for research fellowship.

PY - 2013

Y1 - 2013

N2 - Abnormal N-heterocyclic carbenes of the N-fused heterocycles were employed in stabilizing a series of PEPPSI (Pyridine Enhanced Precatalyst Preparation Stabilization and Initiation) themed complexes of the type (abnormal-NHC) PdI2(pyridine). Specifically, imidazo[1,2-a]pyridine based abnormal complexes, trans-{(1-ethyl-2-(4-R-phenyl)-imidazol-3-ylidene[1,2-a]pyridine)} PdI2(pyridine) [R = F (1b), Cl (2b), Br (3b) and Me (4b)] were synthesized from the reaction of corresponding imidazo[1,2-a]pyridinium iodide salts (1-4)a with PdCl2 in pyridine in the presence of K 2CO3 as a base. The (1-4)b complexes carried out the Sonogashira couplings of the aryl bromide and iodide substrates with terminal alkynes in a mixed aqueous medium in air under the Cu-free and amine-free conditions. The density functional theory studies revealed that in the (1-4)b complexes, the Ccarbene-Pd σ-bonding interaction was significantly stronger than the trans Pd-Npyridine σ-bonding interaction.

AB - Abnormal N-heterocyclic carbenes of the N-fused heterocycles were employed in stabilizing a series of PEPPSI (Pyridine Enhanced Precatalyst Preparation Stabilization and Initiation) themed complexes of the type (abnormal-NHC) PdI2(pyridine). Specifically, imidazo[1,2-a]pyridine based abnormal complexes, trans-{(1-ethyl-2-(4-R-phenyl)-imidazol-3-ylidene[1,2-a]pyridine)} PdI2(pyridine) [R = F (1b), Cl (2b), Br (3b) and Me (4b)] were synthesized from the reaction of corresponding imidazo[1,2-a]pyridinium iodide salts (1-4)a with PdCl2 in pyridine in the presence of K 2CO3 as a base. The (1-4)b complexes carried out the Sonogashira couplings of the aryl bromide and iodide substrates with terminal alkynes in a mixed aqueous medium in air under the Cu-free and amine-free conditions. The density functional theory studies revealed that in the (1-4)b complexes, the Ccarbene-Pd σ-bonding interaction was significantly stronger than the trans Pd-Npyridine σ-bonding interaction.

KW - Abnormal N-heterocyclic carbene (NHC)

KW - Amine-free

KW - Cu-free

KW - DFT studies

KW - Palladium

KW - Sonogashira reaction

UR - http://www.scopus.com/inward/record.url?scp=84884701834&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84884701834&partnerID=8YFLogxK

U2 - 10.1016/j.poly.2013.01.062

DO - 10.1016/j.poly.2013.01.062

M3 - Article

AN - SCOPUS:84884701834

SN - 0277-5387

VL - 64

SP - 20

EP - 29

JO - Polyhedron

JF - Polyhedron

ER -

Palladium complexes of the N-fused heterocycle derived abnormal N-heterocyclic carbenes for the much-preferred Cu-free and the amine-free Sonogashira coupling in air

Abstract

Bibliographical note

Keywords

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