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De S, Hoz S. Quantitation of the Interactions of Alcohols and Amines with SmI 2: Pros and Cons of VIS and NMR Spectroscopies. J Org Chem 2021; 86:10861-10865. [PMID: 34318663 DOI: 10.1021/acs.joc.1c01183] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
While additives play an important role in the reactions of samarium iodide, ligand-SmI2 complexation constants are scarce. Here, VIS spectroscopy was harnessed along with NMR to determine the first complexation constant for most of the alcohols and amines used in SmI2 reactions. The second equilibrium constant was determined for selected ligands. In cases where both methods could be applied, in general, a good correlation between the equilibrium constants was obtained.
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Affiliation(s)
- Suranjan De
- Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel
| | - Shmaryahu Hoz
- Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel
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2
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Abstract
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SmI2 was introduced to organic chemistry as a single
electron transfer agent in 1977. After ca. 15 years of latency, the
scientific community has realized the high potential of this reagent,
and its chemistry has started blooming. This versatile reagent has
mediated a myriad of new bond formations, cyclizations, and other
reactions. Its popularity stems largely from the fact that three different
intermediates, radical anions, radicals, and anions, depending on
the ligand or additive used, could be obtained. Each of these intermediates
could in principle lead to a different product. While these options
vastly enrich the repertoire of SmI2, they necessitate
a thorough mechanistic understanding, especially concerning how appropriate
ligands direct the SmI2 to the desired intermediate. Our
first paper on this subject dealt with the reduction of an activated
double bond. The results were puzzling, especially the H/D isotope
effect, which depended on the order of the reagents addition. This
seminal paper was fundamental to an understanding of how the SmI2 works and enabled us to later explain various phenomena.
For example, it was found that in a given reaction, when MeOH is used
as a proton source, a spiro compound is obtained, while a bicyclic
product is obtained when t-BuOH is used. Our contribution
culminated in formulating guidelines for the rational use of proton
donors in SmI2 reactions. The need to understand
the complexity of the effect of additives
on various processes is nicely demonstrated in photoinduced reactions.
For example, hexamethylphosphoramide (HMPA) enhances the reduction
of anthracene while hampering the reaction of benzyl chloride. The
mechanistic understanding gained enabled us also to broaden the scope
of photostimulated reactions from substrates reacting by a dissociative
electron transfer mechanism to normal reductions, which are difficult
to accomplish at the ground state. Harnessing the classical knowledge
of proton transfer mechanisms to our SmI2 research enabled
us to decipher an old conundrum: why does the combination of water
and amine have such an enhancing effect on the reactivity of SmI2, which is not typical of these two when used separately.
In our studies on the affinity of ligands to SmI2, we discovered
that, in contradistinction to the accepted dogma, SmI2 is
much more azaphilic than it is oxophilic. On the basis of the size
difference between Sm3+ and Sm2+, we developed
a simple diagnostic tool for the nature of the steps following the
electron transfer. The reduction of imines showed that substrate affinity
to SmI2 plays also a crucial role. In these reactions,
new features such as autocatalysis and catalysis by quantum dots were
discovered. Several studies of the ligand effect lead to a clear formulation
of when an inner sphere or outer sphere electron transfer should be
expected. In addition, several reactions where proton-coupled electron
transfer (PCET) is the dominant mechanism were identified. Finally,
the surprisingly old tool of NMR “shift reagents” was
rediscovered and used to directly derive essential information on
the binding constants of ligands and substrates to SmI2.
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Affiliation(s)
- Shmaryahu Hoz
- Department of Chemistry and Institute for Nanotechnology & Advanced Materials, Bar-Ilan University, Ramat Gan 5290002, Israel
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3
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Nimkar A, Maity S, Flowers RA, Hoz S. Contrasting Effect of Additives on Photoinduced Reactions of SmI 2. Chemistry 2019; 25:10499-10504. [PMID: 31150561 DOI: 10.1002/chem.201901997] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 05/30/2019] [Indexed: 11/07/2022]
Abstract
The work described herein compares the effect of additives (HMPA, methanol, ethylene glycol, pinacol, N-methylethanolamine) on thermal and photochemical reactions of samarium diiodide (SmI2 ). In thermal reactions, additives that coordinate to SmI2 induce a significant increase in reaction rate. In photochemical reactions, the presence of an electronegative atom with a highly localized negative charge on the substrate leads to a rate deceleration. In order to benefit from the columbic interaction with the positively charged samarium cation, these substrates react preferentially by an inner sphere reduction mechanism. The addition of ligands prevents this close interaction causing rate retardation. Furthermore, studies demonstrate that excited state quenching of SmII by ethylene glycol and other additives indicate that it is unlikely to be the major cause for the observed rate retardation. This effect provides a simple diagnostic tool to distinguish between an inner and an outer sphere reduction mechanism.
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Affiliation(s)
- Amey Nimkar
- Department of Chemistry, Bar-Ilan University, Ramat Gan, 5290002, Israel
| | - Sandeepan Maity
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania, 18015, USA
| | - Robert A Flowers
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania, 18015, USA
| | - Shmaryahu Hoz
- Department of Chemistry, Bar-Ilan University, Ramat Gan, 5290002, Israel
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4
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Abstract
Ligation plays a multifaceted role in the chemistry of SmI2. Depending on the ligand, two of its major effects are increasing the reduction potential of SmI2, and in the case of a ligand, which is also a proton donor, it may also enhance the reaction by protonation of the radical anion generated in the preceding step. It turns out that the number of ligand molecules that are needed to maximize the reduction potential of SmI2 is significantly smaller than the number of ligand molecules needed for a maximal enhancement of the protonation rate. In addition to the economical use of the ligand, this information can also be utilized as a diagnostic tool for the reaction mechanism in differentiating between single and multistep processes. The possible pitfalls in applying this diagnostic tool to PCET and cyclization reactions are discussed.
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Affiliation(s)
- Sandeepan Maity
- Department of Chemistry , Bar-Ilan University , Ramat Gan 5290002 , Israel
| | - Amey Nimkar
- Department of Chemistry , Bar-Ilan University , Ramat Gan 5290002 , Israel
| | - Shmaryahu Hoz
- Department of Chemistry , Bar-Ilan University , Ramat Gan 5290002 , Israel
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5
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Kovacs D, Borbas KE. The role of photoinduced electron transfer in the quenching of sensitized Europium emission. Coord Chem Rev 2018. [DOI: 10.1016/j.ccr.2018.03.004] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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6
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Abstract
This account describes lanthanide coordination chemistry with a focus on the similarities between lanthanide complexes used in catalysis and those used as contrast agents in magnetic resonance imaging.
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Affiliation(s)
- Matthew J. Allen
- Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, MI 48202, United States, Fax: 313-577-8822
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7
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Hoz S. Physical Organic Chemistry (POC) Makes Chemistry a Science: A Personal Reflection on POC. Isr J Chem 2016. [DOI: 10.1002/ijch.201400183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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8
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Maity S, Hoz S. Deciphering a 20-Year-Old Conundrum: The Mechanisms of Reduction by the Water/Amine/SmI2Mixture. Chemistry 2015; 21:18394-400. [PMID: 26525449 DOI: 10.1002/chem.201503104] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Indexed: 11/07/2022]
Affiliation(s)
- Sandeepan Maity
- Department of Chemistry, Bar-Ilan University, Ramat Gan, 52900 (Israel)
| | - Shmaryahu Hoz
- Department of Chemistry, Bar-Ilan University, Ramat Gan, 52900 (Israel).
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9
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Yella R, Hoz S. Channeling the SmI2 Reactions to the Radical Path: Radicals Resisting Reduction by SmI2. Org Lett 2014; 16:3876-9. [PMID: 25030208 DOI: 10.1021/ol501490f] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ramesh Yella
- Department
of Chemistry, Bar-Illan University, Ramat-Gan 52900, Israel
| | - Shmaryahu Hoz
- Department
of Chemistry, Bar-Illan University, Ramat-Gan 52900, Israel
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10
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Yoshimura A, Tomisaka Y, Li Z, Nomoto A, Ogawa A. Photoinduced Reductive Coupling of Organochlorosilanes with SmI2/Sm. HETEROATOM CHEMISTRY 2014. [DOI: 10.1002/hc.21186] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Aya Yoshimura
- Department of Applied Chemistry; Graduate School of Engineering; Osaka Prefecture University; Sakai Osaka 599-8531 Japan
| | - Yuri Tomisaka
- Department of Applied Chemistry; Graduate School of Engineering; Osaka Prefecture University; Sakai Osaka 599-8531 Japan
| | - Zhifang Li
- Key Laboratory of Organosilicon Chemistry; Hangzhou Normal University; Hangzhou 310012 People's Republic of China
| | - Akihiro Nomoto
- Department of Applied Chemistry; Graduate School of Engineering; Osaka Prefecture University; Sakai Osaka 599-8531 Japan
| | - Akiya Ogawa
- Department of Applied Chemistry; Graduate School of Engineering; Osaka Prefecture University; Sakai Osaka 599-8531 Japan
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11
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Szostak M, Fazakerley NJ, Parmar D, Procter DJ. Cross-Coupling Reactions Using Samarium(II) Iodide. Chem Rev 2014; 114:5959-6039. [DOI: 10.1021/cr400685r] [Citation(s) in RCA: 290] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Michal Szostak
- School
of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Neal J. Fazakerley
- School
of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Dixit Parmar
- School
of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - David J. Procter
- School
of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
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12
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Halder S, Hoz S. Hydroxylated HMPA Enhances both Reduction Potential and Proton Donation in SmI2 Reactions. J Org Chem 2014; 79:2682-7. [DOI: 10.1021/jo500161s] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Sandipan Halder
- Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel
| | - Shmaryahu Hoz
- Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel
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13
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Maity S, Prasad E. Photoinduced electron transfer from Eu(II)-complexes to organic molecules: Rate and mechanistic investigation. J Photochem Photobiol A Chem 2014. [DOI: 10.1016/j.jphotochem.2013.10.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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14
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Rao CN, Hoz S. Synergism and Inhibition in the Combination of Visible Light and HMPA in SmI2 Reductions. J Org Chem 2012; 77:9199-204. [DOI: 10.1021/jo3017814] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
| | - Shmaryahu Hoz
- Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel
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15
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Szostak M, Procter DJ. Jenseits von Samariumdiiodid: Perspektiven für Lanthanoid(II)-vermittelte Reduktionen. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201201065] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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16
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Szostak M, Procter DJ. Beyond Samarium Diiodide: Vistas in Reductive Chemistry Mediated by Lanthanides(II). Angew Chem Int Ed Engl 2012; 51:9238-56. [DOI: 10.1002/anie.201201065] [Citation(s) in RCA: 134] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Revised: 04/03/2012] [Indexed: 11/11/2022]
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Affiliation(s)
| | - Shmaryahu Hoz
- Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel
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18
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Maity S, Choquette KA, Flowers RA, Prasad E. Effect of Crown Ethers on the Ground and Excited State Reactivity of Samarium Diiodide in Acetonitrile. J Phys Chem A 2012; 116:2154-60. [DOI: 10.1021/jp212247a] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sandeepan Maity
- Department of Chemistry, Indian Institute of Technology Madras, Chennai 600
036, India
| | - Kimberly A. Choquette
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, United
States
| | - Robert A. Flowers
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, United
States
| | - Edamana Prasad
- Department of Chemistry, Indian Institute of Technology Madras, Chennai 600
036, India
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19
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Szostak M, Spain M, Parmar D, Procter DJ. Selective reductive transformations using samarium diiodide-water. Chem Commun (Camb) 2012; 48:330-46. [DOI: 10.1039/c1cc14252f] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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20
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Upadhyay SK, Hoz S. The Effect of Proton Donors on the Facial Stereoselectivity in SmI2 Reduction of Norcamphor. J Org Chem 2011; 76:1355-60. [DOI: 10.1021/jo1023206] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | - Shmaryahu Hoz
- Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel
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