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Sah C, Saraswat M, Jacob L, Venkataramani S. Insights on unimolecular and bimolecular reactivity patterns of pyridyl, pyridyl-N-oxide, and pyridinyl radicals through spin density. COMPUT THEOR CHEM 2020. [DOI: 10.1016/j.comptc.2020.113025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Saraswat M, Venkataramani S. Through bond and through space interactions in dehydro-diazine radicals: a case study of 3c-5e interactions. Phys Chem Chem Phys 2018; 20:4386-4395. [PMID: 29369313 DOI: 10.1039/c7cp07579k] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Owing to the 3c-5e (3-centred-5-electrons) interactions between two nitrogen lone pairs and a radical electron, the dehydrodiazine radical isomers are very interesting from the fundamental point of view. Among them, pyrimidine has three (1a-1c), pyridazine has two (2a and 2b) and pyrazine has only one (3a) radical isomer. Based on quantum chemical calculations at the (U)B3LYP, (U)M06-2X, (U)BLYP, CBS-QB3 and (U)CCSD(T) levels with cc-pVTZ as the basis set, we found the 4-dehydropyrimidine (1b) radical to be the most stable isomer among the three pyrimidine radicals, followed by the 2-dehydropyrimidine (1a) and 5-dehydropyrimidine (1c) radical isomers. In the case of pyridazine, 3-dehydro radical isomer (2a) is more stable than 4-dehydropyridazine (2b). Bond dissociation energy (BDE) calculations and estimation of radical stabilization energies (RSE) using isodesmic reactions revealed the stability order among the six isomeric diazine radicals as 1c < 2b < 2a < 1a < 3a < 1b. Spin densities at each radical centre and non-zero values at nitrogen centres provided information about the extent of delocalization of radical electrons, which was consistent with the relative stability order of all the isomers. The multiconfigurational CASSCF and natural bond orbital (NBO) calculations suggested the presence of direct through space interactions (between lone pairs and a radical, TS) that play a dominant role over the through bond (through intervening bonds, TB) interactions in deciding the stability order. To confirm these results, we have also estimated the proton affinities (PAs) for each nitrogen atom and compared them with their respective parent diazines, where lowering of the PA values convincingly envisaged the extent and strength of interactions between the nitrogen and radical centre. Atoms-in-molecules (AIM) analysis and estimation of hyperfine coupling constants have also been performed to verify these results. All these results showed that the through space interaction between the lone pair and the radical electron is very important for the electronic structural and stability aspects in dehydrodiazine radicals.
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Affiliation(s)
- Mayank Saraswat
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector-81, Knowledge City, SAS Nagar, Mohali, Punjab - 140306, India.
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Sah C, Jacob L, Saraswat M, Venkataramani S. Does a Nitrogen Lone Pair Lead to Two Centered-Three Electron (2c-3e) Interactions in Pyridyl Radical Isomers? J Phys Chem A 2017; 121:3781-3791. [PMID: 28423280 DOI: 10.1021/acs.jpca.7b01501] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Each of the three isomeric pyridyl radicals (2-, 3-, and 4-dehydropyridines) contains a lone pair and an unpaired electron. As a result, a potential two centered-three electron interaction between the radical electron and the lone pair through-space (TS) and/or through-bond (TB) can exist that may influence the stability of the radicals. Due to the change in geometrical positions relative to each other, the strength of interaction can be varied. In this study, we investigated the structural and stability aspects of pyridyl radical isomers with a major emphasis on the interaction of a nitrogen lone pair with the radical center. In order to obtain evidence for such interactions, protonated and N-oxide analogues of the corresponding isomeric pyridyl radicals have been considered in such a way to understand the consequences due to unavailability of the lone pair. Similarly, electron attachment and detachment energies at the radical center (vertical detachment energy, VDE, of corresponding anions and vertical ionization energy, VIE, of radical isomers) have been calculated to find out the interaction trend upon modification at the radical center. Different levels of theory including (U)B3LYP/cc-pVTZ, (U)M06/cc-pVTZ, CBS-QB3, single-point energy calculations at (U)CCSD(T)/cc-pVTZ, and multireference CASSCF/cc-pVTZ methods have been employed in this regard. A closer inspection of geometries, relative stability order, spin density, electrostatic potential, molecular orbitals, NBO analysis, and vibrational analysis have showed a strong and stabilizing TS interaction between the radical center and the lone pair in the case of the 2-pyridyl radical. On the other hand, the 4-pyridyl radical showed stabilizing interactions only via TB coupling, whereas the TS interaction is nonexistent. Despite the presence of both interactions in the case of the 3-pyridyl radical, their overall influence is less effective toward stability.
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Affiliation(s)
- Chitranjan Sah
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali , Sector 81, SAS Nagar, Knowledge City, Mohali, Punjab 140306, India
| | - Lilit Jacob
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali , Sector 81, SAS Nagar, Knowledge City, Mohali, Punjab 140306, India
| | - Mayank Saraswat
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali , Sector 81, SAS Nagar, Knowledge City, Mohali, Punjab 140306, India
| | - Sugumar Venkataramani
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali , Sector 81, SAS Nagar, Knowledge City, Mohali, Punjab 140306, India
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Mukhopadhyay A, Jacob L, Venkataramani S. Dehydro-oxazole, thiazole and imidazole radicals: insights into the electronic structure, stability and reactivity aspects. Phys Chem Chem Phys 2017; 19:394-407. [DOI: 10.1039/c6cp05677f] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Computations on the effect of heteroatoms in the structural, stability and reactivity aspects of the oxazole, thiazole and imidazole radicals.
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Affiliation(s)
- Anamika Mukhopadhyay
- Department of Chemical Sciences
- Indian Institute of Science Education and Research
- IISER Mohali
- Mohali
- India
| | - Lilit Jacob
- Department of Chemical Sciences
- Indian Institute of Science Education and Research
- IISER Mohali
- Mohali
- India
| | - Sugumar Venkataramani
- Department of Chemical Sciences
- Indian Institute of Science Education and Research
- IISER Mohali
- Mohali
- India
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Goetz AE, Shah TK, Garg NK. Pyridynes and indolynes as building blocks for functionalized heterocycles and natural products. Chem Commun (Camb) 2015; 51:34-45. [DOI: 10.1039/c4cc06445c] [Citation(s) in RCA: 202] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
This feature article showcases the use of pyridynes and indolynes to construct functionalized heterocycles and complex natural products.
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Affiliation(s)
- Adam E. Goetz
- Department of Chemistry and Biochemistry
- University of California
- Los Angeles
- USA
| | - Tejas K. Shah
- Department of Chemistry and Biochemistry
- University of California
- Los Angeles
- USA
| | - Neil K. Garg
- Department of Chemistry and Biochemistry
- University of California
- Los Angeles
- USA
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Williams PE, Jankiewicz BJ, Yang L, Kenttämaa HI. Properties and reactivity of gaseous distonic radical ions with aryl radical sites. Chem Rev 2013; 113:6949-85. [PMID: 23987564 PMCID: PMC3889672 DOI: 10.1021/cr400121w] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Peggy E. Williams
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47906
| | | | - Linan Yang
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47906
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Hossain E, Wenthold PG. Singlet stabilization of oxazole- and isoxazolenitrene-n-oxides by radical delocalization. COMPUT THEOR CHEM 2013. [DOI: 10.1016/j.comptc.2013.07.028] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Affiliation(s)
- Manabu Abe
- Department of Chemistry, Graduate School of Science, Hiroshima University (HIRODAI), 1-3-1 Kagamiyama, Higashi-Hiroshima,
Hiroshima 739-8526, Japan
- Institute for Molecular Science (IMS), Okazaki, Aichi 444-8787,
Japan
- JST-CREST, 5
Sanbancho,
Chiyodaku, Tokyo 102-0075, Japan
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Goetz AE, Garg NK. Regioselective reactions of 3,4-pyridynes enabled by the aryne distortion model. Nat Chem 2012; 5:54-60. [PMID: 23247178 PMCID: PMC3531798 DOI: 10.1038/nchem.1504] [Citation(s) in RCA: 177] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Accepted: 10/18/2012] [Indexed: 12/23/2022]
Abstract
The pyridine heterocycle continues to play a vital role in the development of human medicines. More than 100 currently-marketed drugs contain this privileged unit, which remains highly sought after synthetically. We report an efficient means to access di- and tri-substituted pyridines in an efficient and highly controlled manner using transient 3,4-pyridyne intermediates. Previous efforts to employ 3,4-pyridynes for the construction of substituted pyridines have been hampered by a lack of regiocontrol or the inability to later manipulate an adjacent directing group. The newly developed strategy relies on the use of proximal halide or sulfamate substituents to perturb pyridyne distortion, which in turn governs regioselectivities in nucleophilic addition and cycloaddition reactions. Following trapping of in situ-generated pyridynes, the neighboring directing groups may be removed or exploited using versatile metal-catalyzed cross-coupling reactions. This methodology now renders 3,4-pyridynes useful synthetic building blocks for the creation of highly decorated derivatives of the medicinally privileged pyridine heterocycle.
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Affiliation(s)
- Adam E Goetz
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, USA
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Wang T, Zhang H, Han F, Lin R, Lin Z, Xia H. Synthesis and Characterization of a Metallapyridyne Complex. Angew Chem Int Ed Engl 2012; 51:9838-41. [DOI: 10.1002/anie.201204073] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2012] [Indexed: 11/10/2022]
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Wang T, Zhang H, Han F, Lin R, Lin Z, Xia H. Synthesis and Characterization of a Metallapyridyne Complex. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201204073] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Goetz AE, Bronner SM, Cisneros JD, Melamed JM, Paton RS, Houk KN, Garg NK. An efficient computational model to predict the synthetic utility of heterocyclic arynes. Angew Chem Int Ed Engl 2012; 51:2758-62. [PMID: 22307724 PMCID: PMC4502420 DOI: 10.1002/anie.201108863] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Indexed: 11/08/2022]
Abstract
Think before you act: a computational approach is reported for evaluating the synthetic potential of heterocyclic arynes. Routine and rapid calculations of arene dehydrogenation energies and aryne angle distortion predict the likelihood that a given hetaryne can be generated, as well as the degree of regioselectivity expected in a reaction between a given hetaryne and a nucleophilic trapping agent.
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Affiliation(s)
- Adam E. Goetz
- Department of Chemistry and Biochemistry University of California, Los Angeles Los Angeles, CA 90095 (USA)
| | - Sarah M. Bronner
- Department of Chemistry and Biochemistry University of California, Los Angeles Los Angeles, CA 90095 (USA)
| | - Jordan D. Cisneros
- Department of Chemistry and Biochemistry University of California, Los Angeles Los Angeles, CA 90095 (USA)
| | - Joshua M. Melamed
- Department of Chemistry and Biochemistry University of California, Los Angeles Los Angeles, CA 90095 (USA)
| | - Robert S. Paton
- Department of Chemistry and Biochemistry University of California, Los Angeles Los Angeles, CA 90095 (USA)
- Chemistry Research Laboratory University of Oxford, Mansfield Road, Oxford OX1 3TA, UK
| | - K. N. Houk
- Department of Chemistry and Biochemistry University of California, Los Angeles Los Angeles, CA 90095 (USA)
| | - Neil K. Garg
- Department of Chemistry and Biochemistry University of California, Los Angeles Los Angeles, CA 90095 (USA)
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Goetz AE, Bronner SM, Cisneros JD, Melamed JM, Paton RS, Houk KN, Garg NK. An Efficient Computational Model to Predict the Synthetic Utility of Heterocyclic Arynes. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201108863] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Wenthold PG. Spin-State Dependent Radical Stabilization in Nitrenes: The Unusually Small Singlet–Triplet Splitting in 2-Furanylnitrene. J Org Chem 2011; 77:208-14. [DOI: 10.1021/jo2016967] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Paul G. Wenthold
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084,
United States
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