Michael addition of cyclic β-oxo ester and α-methyl cyano ester substrates with activated olefins by iron complexes of benzimidazole derived N-heterocyclic carbene ligands

A.P. Prakasham; Manoj Kumar Gangwar; Prasenjit Ghosh

doi:10.1016/j.jorganchem.2018.01.061

Michael addition of cyclic β-oxo ester and α-methyl cyano ester substrates with activated olefins by iron complexes of benzimidazole derived N-heterocyclic carbene ligands

A.P. Prakasham, Manoj Kumar Gangwar, Prasenjit Ghosh

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

18 Citations (Scopus)

Abstract

Michael addition reactions of cyclic β-oxo ester and α-methyl cyano ester substrates with acceptor activated olefins were catalyzed by iron N−heterocyclic carbene (NHC) complexes of the type, {Cp[1-benzyl-3-alkyl-benzimidazol-2-ylidene]Fe(CO)₂}I, where [alkyl = i-Pr (1) and Et (2)] in the presence of L-proline as chiral auxiliary under ambient conditions. In case of the cyclic β-oxo ester substrates good yields of up to 68% and enantioselectivities of up to 18% were observed while for the α-methyl cyano ester substrates similar yields of up to 82% and enantioselectivities of up to 8% were observed. Notably, for the cyclic β-oxo ester substrates, the five membered ethyl-2-oxocyclopentane-1-carboxylate gave superior yields and enantioselectivities over the six membered ethyl-2-oxocyclohexane-1-carboxylate. In case of α-methyl cyano ester substrates, methyl vinyl ketone gave higher yields as compared to the other acceptor activated olefins namely, ethyl vinyl ketone and acrylonitrile. Based on the mass spectrometry studies, that detected the presence of L-proline adduct species (1–2)A, L-proline and substrate adduct species (1–2)B and L-proline and product adduct species (1–2)C in the catalysis reaction mixture, a mechanistic cycle has been proposed for the Fe−NHC mediated Michael addition reaction.

Original language	English
Pages (from-to)	106-116
Number of pages	11
Journal	Journal of Organometallic Chemistry
Volume	859
DOIs	https://doi.org/10.1016/j.jorganchem.2018.01.061
Publication status	Published - 15 Mar 2018
Externally published	Yes

Bibliographical note

Funding Information:
We thank the Department of Science and Technology (EMR/2014/000254), New Delhi, India, for financial support of this research. We gratefully acknowledge the Single Crystal X-ray Diffraction Facility, Department of Chemistry, IIT Bombay, Mumbai, India, for the crystallographic characterization data. A.P.P. and M.K.G thank CSIR, New Delhi, India, for research fellowships.

Funding Information:
We thank the Department of Science and Technology ( EMR/2014/000254 ), New Delhi, India, for financial support of this research. We gratefully acknowledge the Single Crystal X-ray Diffraction Facility, Department of Chemistry, IIT Bombay, Mumbai, India, for the crystallographic characterization data. A.P.P. and M.K.G thank CSIR, New Delhi, India, for research fellowships. Appendix A

Publisher Copyright:
© 2018 Elsevier B.V.

Funding

We thank the Department of Science and Technology (EMR/2014/000254), New Delhi, India, for financial support of this research. We gratefully acknowledge the Single Crystal X-ray Diffraction Facility, Department of Chemistry, IIT Bombay, Mumbai, India, for the crystallographic characterization data. A.P.P. and M.K.G thank CSIR, New Delhi, India, for research fellowships. We thank the Department of Science and Technology ( EMR/2014/000254 ), New Delhi, India, for financial support of this research. We gratefully acknowledge the Single Crystal X-ray Diffraction Facility, Department of Chemistry, IIT Bombay, Mumbai, India, for the crystallographic characterization data. A.P.P. and M.K.G thank CSIR, New Delhi, India, for research fellowships. Appendix A

Keywords

Asymmetric catalysis
Benzimidazole ligands
Cyclic β-oxo ester
Iron complexes
L-proline
Mass spectrometry
Michael addition
N−heterocyclic carbenes
α-Methyl cyano ester

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10.1016/j.jorganchem.2018.01.061

Cite this

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title = "Michael addition of cyclic β-oxo ester and α-methyl cyano ester substrates with activated olefins by iron complexes of benzimidazole derived N-heterocyclic carbene ligands",

abstract = "Michael addition reactions of cyclic β-oxo ester and α-methyl cyano ester substrates with acceptor activated olefins were catalyzed by iron N−heterocyclic carbene (NHC) complexes of the type, {Cp[1-benzyl-3-alkyl-benzimidazol-2-ylidene]Fe(CO)2}I, where [alkyl = i-Pr (1) and Et (2)] in the presence of L-proline as chiral auxiliary under ambient conditions. In case of the cyclic β-oxo ester substrates good yields of up to 68% and enantioselectivities of up to 18% were observed while for the α-methyl cyano ester substrates similar yields of up to 82% and enantioselectivities of up to 8% were observed. Notably, for the cyclic β-oxo ester substrates, the five membered ethyl-2-oxocyclopentane-1-carboxylate gave superior yields and enantioselectivities over the six membered ethyl-2-oxocyclohexane-1-carboxylate. In case of α-methyl cyano ester substrates, methyl vinyl ketone gave higher yields as compared to the other acceptor activated olefins namely, ethyl vinyl ketone and acrylonitrile. Based on the mass spectrometry studies, that detected the presence of L-proline adduct species (1–2)A, L-proline and substrate adduct species (1–2)B and L-proline and product adduct species (1–2)C in the catalysis reaction mixture, a mechanistic cycle has been proposed for the Fe−NHC mediated Michael addition reaction.",

keywords = "Asymmetric catalysis, Benzimidazole ligands, Cyclic β-oxo ester, Iron complexes, L-proline, Mass spectrometry, Michael addition, N−heterocyclic carbenes, α-Methyl cyano ester",

author = "A.P. Prakasham and Gangwar, {Manoj Kumar} and Prasenjit Ghosh",

note = "Funding Information: We thank the Department of Science and Technology (EMR/2014/000254), New Delhi, India, for financial support of this research. We gratefully acknowledge the Single Crystal X-ray Diffraction Facility, Department of Chemistry, IIT Bombay, Mumbai, India, for the crystallographic characterization data. A.P.P. and M.K.G thank CSIR, New Delhi, India, for research fellowships. Funding Information: We thank the Department of Science and Technology ( EMR/2014/000254 ), New Delhi, India, for financial support of this research. We gratefully acknowledge the Single Crystal X-ray Diffraction Facility, Department of Chemistry, IIT Bombay, Mumbai, India, for the crystallographic characterization data. A.P.P. and M.K.G thank CSIR, New Delhi, India, for research fellowships. Appendix A Publisher Copyright: {\textcopyright} 2018 Elsevier B.V.",

year = "2018",

month = mar,

day = "15",

doi = "10.1016/j.jorganchem.2018.01.061",

language = "English",

volume = "859",

pages = "106--116",

journal = "Journal of Organometallic Chemistry",

issn = "0022-328X",

publisher = "Elsevier B.V.",

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Michael addition of cyclic β-oxo ester and α-methyl cyano ester substrates with activated olefins by iron complexes of benzimidazole derived N-heterocyclic carbene ligands. / Prakasham, A.P.; Gangwar, Manoj Kumar; Ghosh, Prasenjit.
In: Journal of Organometallic Chemistry, Vol. 859, 15.03.2018, p. 106-116.

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

TY - JOUR

T1 - Michael addition of cyclic β-oxo ester and α-methyl cyano ester substrates with activated olefins by iron complexes of benzimidazole derived N-heterocyclic carbene ligands

AU - Prakasham, A.P.

AU - Gangwar, Manoj Kumar

AU - Ghosh, Prasenjit

N1 - Funding Information: We thank the Department of Science and Technology (EMR/2014/000254), New Delhi, India, for financial support of this research. We gratefully acknowledge the Single Crystal X-ray Diffraction Facility, Department of Chemistry, IIT Bombay, Mumbai, India, for the crystallographic characterization data. A.P.P. and M.K.G thank CSIR, New Delhi, India, for research fellowships. Funding Information: We thank the Department of Science and Technology ( EMR/2014/000254 ), New Delhi, India, for financial support of this research. We gratefully acknowledge the Single Crystal X-ray Diffraction Facility, Department of Chemistry, IIT Bombay, Mumbai, India, for the crystallographic characterization data. A.P.P. and M.K.G thank CSIR, New Delhi, India, for research fellowships. Appendix A Publisher Copyright: © 2018 Elsevier B.V.

PY - 2018/3/15

Y1 - 2018/3/15

N2 - Michael addition reactions of cyclic β-oxo ester and α-methyl cyano ester substrates with acceptor activated olefins were catalyzed by iron N−heterocyclic carbene (NHC) complexes of the type, {Cp[1-benzyl-3-alkyl-benzimidazol-2-ylidene]Fe(CO)2}I, where [alkyl = i-Pr (1) and Et (2)] in the presence of L-proline as chiral auxiliary under ambient conditions. In case of the cyclic β-oxo ester substrates good yields of up to 68% and enantioselectivities of up to 18% were observed while for the α-methyl cyano ester substrates similar yields of up to 82% and enantioselectivities of up to 8% were observed. Notably, for the cyclic β-oxo ester substrates, the five membered ethyl-2-oxocyclopentane-1-carboxylate gave superior yields and enantioselectivities over the six membered ethyl-2-oxocyclohexane-1-carboxylate. In case of α-methyl cyano ester substrates, methyl vinyl ketone gave higher yields as compared to the other acceptor activated olefins namely, ethyl vinyl ketone and acrylonitrile. Based on the mass spectrometry studies, that detected the presence of L-proline adduct species (1–2)A, L-proline and substrate adduct species (1–2)B and L-proline and product adduct species (1–2)C in the catalysis reaction mixture, a mechanistic cycle has been proposed for the Fe−NHC mediated Michael addition reaction.

AB - Michael addition reactions of cyclic β-oxo ester and α-methyl cyano ester substrates with acceptor activated olefins were catalyzed by iron N−heterocyclic carbene (NHC) complexes of the type, {Cp[1-benzyl-3-alkyl-benzimidazol-2-ylidene]Fe(CO)2}I, where [alkyl = i-Pr (1) and Et (2)] in the presence of L-proline as chiral auxiliary under ambient conditions. In case of the cyclic β-oxo ester substrates good yields of up to 68% and enantioselectivities of up to 18% were observed while for the α-methyl cyano ester substrates similar yields of up to 82% and enantioselectivities of up to 8% were observed. Notably, for the cyclic β-oxo ester substrates, the five membered ethyl-2-oxocyclopentane-1-carboxylate gave superior yields and enantioselectivities over the six membered ethyl-2-oxocyclohexane-1-carboxylate. In case of α-methyl cyano ester substrates, methyl vinyl ketone gave higher yields as compared to the other acceptor activated olefins namely, ethyl vinyl ketone and acrylonitrile. Based on the mass spectrometry studies, that detected the presence of L-proline adduct species (1–2)A, L-proline and substrate adduct species (1–2)B and L-proline and product adduct species (1–2)C in the catalysis reaction mixture, a mechanistic cycle has been proposed for the Fe−NHC mediated Michael addition reaction.

KW - Asymmetric catalysis

KW - Benzimidazole ligands

KW - Cyclic β-oxo ester

KW - Iron complexes

KW - L-proline

KW - Mass spectrometry

KW - Michael addition

KW - N−heterocyclic carbenes

KW - α-Methyl cyano ester

UR - http://www.scopus.com/inward/record.url?scp=85041823277&partnerID=8YFLogxK

U2 - 10.1016/j.jorganchem.2018.01.061

DO - 10.1016/j.jorganchem.2018.01.061

M3 - Article

AN - SCOPUS:85041823277

SN - 0022-328X

VL - 859

SP - 106

EP - 116

JO - Journal of Organometallic Chemistry

JF - Journal of Organometallic Chemistry

ER -

Michael addition of cyclic β-oxo ester and α-methyl cyano ester substrates with activated olefins by iron complexes of benzimidazole derived N-heterocyclic carbene ligands

Abstract

Bibliographical note

Funding

Keywords

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