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Chang TY, Adrion DM, Meyer AR, Lopez SA, Garcia-Garibay MA. A Green Chemistry Approach toward the Stereospecific Synthesis of Densely Functionalized Cyclopropanes via the Solid-State Photodenitrogenation of Crystalline 1-Pyrazolines. J Org Chem 2022; 87:2277-2288. [PMID: 35041410 DOI: 10.1021/acs.joc.1c01808] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The cyclopropane ring features prominently in active pharmaceuticals, and this has spurred the development of synthetic methodologies that effectively incorporate this highly strained motif into such molecules. As such, elegant solutions to prepare densely functionalized cyclopropanes, particularly ones embedded within the core of complex structures, have become increasingly sought-after. Here we report the stereospecific synthesis of a set of cyclopropanes with vicinal quaternary stereocenters via the solvent-free solid-state photodenitrogenation of crystalline 1-pyrazolines. Density functional theory calculations at the M062X/6-31+G(d,p) level of theory were used to determine the origin of regioselectivity for the synthesis of the 1-pyrazolines; favorable in-phase frontier molecular orbital interactions are responsible for the observation of a single pyrazoline regioisomer. It was also shown that the loss of N2 may take place via a highly selective solid-state thermal reaction. Scalability of the solid-state photoreaction is enabled through aqueous nanocrystalline suspensions, making this method a "greener" alternative to effectively facilitate the construction of cyclopropane-containing molecular scaffolds.
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Affiliation(s)
- Trevor Y Chang
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
| | - Daniel M Adrion
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts 02115, United States
| | - Alana Rose Meyer
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
| | - Steven A Lopez
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts 02115, United States
| | - Miguel A Garcia-Garibay
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
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Abe M, Watanabe S, Tamura H, Boinapally S, Kanahara K, Fujiwara Y. Substituent effect on reactivity of triplet excited state of 2,3-diazabicyclo[2.2.1]hept-2-enes, DBH derivatives: α C-N bond cleavage versus β C-C bond cleavage. J Org Chem 2012; 78:1940-8. [PMID: 22985271 DOI: 10.1021/jo3019472] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The photoreaction of a series of 2,3-diazabicyclo[2.2.1]hept-2-ene (DBH) derivatives, in which various substituents (X) were introduced at the methano bridge carbon of C(7), was investigated under direct (>290 nm) and triplet-sensitized (Ph2CO, >370 nm) irradiation conditions of the azo chromophore (−Cβ–Cα–N═N–Cα–Cβ−). The azo compounds offered a unique opportunity to see the substituent X effect at the remote position of the azo chromophore on the reactivity of the triplet excited state of bicyclic azoalkanes. The present study led to the first observation of the unusual Cα–Cβ bond-cleavage reaction without the ring stiffness, that is, the structural rigidity, in the triplet state of the cyclic azoalkanes. The stereoelectronic effects were found to play an important role in lowering the activation energy of the Cα–Cβ bond-cleavage reaction. NBO analyses at the M06-2X/cc-PVDZ level of theory confirmed the stereoelectronic effect.
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Affiliation(s)
- Manabu Abe
- Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan.
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Shiraki S, Vogelsberg CS, Garcia-Garibay MA. Solid-state photochemistry of crystalline pyrazolines: reliable generation and reactivity control of 1,3-biradicals and their potential for the green chemistry synthesis of substituted cyclopropanes. Photochem Photobiol Sci 2012; 11:1929-37. [DOI: 10.1039/c2pp25263e] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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4
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Nau WM. Pathways for the photochemical hydrogen abstraction by n, π*-excited states. ACTA ACUST UNITED AC 2010. [DOI: 10.1002/bbpc.19981020329] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Anbazhagan V, Kandavelu V, Kathiravan A, Renganathan R. Investigation on the fluorescence quenching of 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) by certain estrogens and catechols. J Photochem Photobiol A Chem 2008. [DOI: 10.1016/j.jphotochem.2007.06.026] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Pischel U, Nau WM. Structure-reactivity relationships in the photoreduction of n,pi*-excited ketones and azoalkanes: the effect of reaction thermodynamics, excited-state electrophilicity, and antibonding character in the transition state. Photochem Photobiol Sci 2002; 1:141-7. [PMID: 12659131 DOI: 10.1039/b110108k] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reaction enthalpies for the photoreduction of n,pi*-excited states (acetone, benzophenone, 2.3-diazabicyclo[2.2.2]oct-2-ene, and a 2,3-diazabicyclo[2.2.1]hept-2-ene derivative) by model hydrogen donors (methanol and dimethylamine) were calculated on the basis of a critically evaluated data set of bond dissociation energies for donors and reduced acceptors. These were compared with the observed photoreactivity, which can be assessed through quenching rate constants of the excited states by hydrogen donors. The intriguing observation of a preferential attack at electrophilic hydrogen atoms, i.e., N-H or O-H, by n,pi*-excited azoalkanes is rationalised on the basis of the calculated thermochemical data, differences in electrophilicity, and varying contributions of antibonding character in the transition state. Singlet-excited azoalkanes act as nucleophilic species, while excited ketones display an electrophilic reactivity. This is in line with the pictorial description of the electron distribution in these excited states.
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Affiliation(s)
- Uwe Pischel
- Departement Chemie, Universität Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
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Spichty M, Turro NJ, Rist G, Birbaum JL, Dietliker K, Wolf JP, Gescheidt G. Bond cleavage in the excited state of acyl phosphene oxides. J Photochem Photobiol A Chem 2001. [DOI: 10.1016/s1010-6030(01)00515-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Hartmann H, Noack A. AlkylenverbrückteN,N,N′,N′-tetrasubstituierte Bis(2-amino-5-thiazolyl)methinium-Salze - eine neue Klasse stark fluoreszierender Farbstoffe. Angew Chem Int Ed Engl 2001. [DOI: 10.1002/1521-3757(20010202)113:3<597::aid-ange597>3.0.co;2-s] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Hartmann H, Noack A. Alkylene-bridged N,N,N′N′-Tetrasubstituted Bis(2-amino-5-thiazolyl)methinium Salts-A New Class of Strongly Fluorescent Dyes. Angew Chem Int Ed Engl 2001; 40:552-554. [DOI: 10.1002/1521-3773(20010202)40:3<552::aid-anie552>3.0.co;2-c] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2000] [Indexed: 11/12/2022]
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Uppili S, Marti V, Nikolaus A, Jockusch S, Adam W, Engel PS, Turro NJ, Ramamurthy V. Heavy-Cation-Induced Phosphorescence of Alkanones and Azoalkanes in Zeolites As Hosts: Induced S1 (nπ*) to T1 (nπ*) Intersystem Crossing and S0 to T1 (nπ*) Absorption. J Am Chem Soc 2000. [DOI: 10.1021/ja001845d] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sundararajan Uppili
- Department of Chemistry, Tulane University New Orleans, Louisiana 70118 Institut fuer Organische Chemie der Universitat Würzburg Am Humbland, D-97074, Würzburg, Germany Department of Chemistry, Rice University Houston, Texas 77005 Department of Chemistry, Columbia University New York, New York 10027
| | - Vincenti Marti
- Department of Chemistry, Tulane University New Orleans, Louisiana 70118 Institut fuer Organische Chemie der Universitat Würzburg Am Humbland, D-97074, Würzburg, Germany Department of Chemistry, Rice University Houston, Texas 77005 Department of Chemistry, Columbia University New York, New York 10027
| | - Achim Nikolaus
- Department of Chemistry, Tulane University New Orleans, Louisiana 70118 Institut fuer Organische Chemie der Universitat Würzburg Am Humbland, D-97074, Würzburg, Germany Department of Chemistry, Rice University Houston, Texas 77005 Department of Chemistry, Columbia University New York, New York 10027
| | - Steffen Jockusch
- Department of Chemistry, Tulane University New Orleans, Louisiana 70118 Institut fuer Organische Chemie der Universitat Würzburg Am Humbland, D-97074, Würzburg, Germany Department of Chemistry, Rice University Houston, Texas 77005 Department of Chemistry, Columbia University New York, New York 10027
| | - Waldemar Adam
- Department of Chemistry, Tulane University New Orleans, Louisiana 70118 Institut fuer Organische Chemie der Universitat Würzburg Am Humbland, D-97074, Würzburg, Germany Department of Chemistry, Rice University Houston, Texas 77005 Department of Chemistry, Columbia University New York, New York 10027
| | - Paul S. Engel
- Department of Chemistry, Tulane University New Orleans, Louisiana 70118 Institut fuer Organische Chemie der Universitat Würzburg Am Humbland, D-97074, Würzburg, Germany Department of Chemistry, Rice University Houston, Texas 77005 Department of Chemistry, Columbia University New York, New York 10027
| | - Nicholas J. Turro
- Department of Chemistry, Tulane University New Orleans, Louisiana 70118 Institut fuer Organische Chemie der Universitat Würzburg Am Humbland, D-97074, Würzburg, Germany Department of Chemistry, Rice University Houston, Texas 77005 Department of Chemistry, Columbia University New York, New York 10027
| | - V. Ramamurthy
- Department of Chemistry, Tulane University New Orleans, Louisiana 70118 Institut fuer Organische Chemie der Universitat Würzburg Am Humbland, D-97074, Würzburg, Germany Department of Chemistry, Rice University Houston, Texas 77005 Department of Chemistry, Columbia University New York, New York 10027
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Munakata M, Ning GL, Kuroda-Sowa T, Maekawa M, Suenaga Y, Horino T. Construction of Copper(I) Coordination Polymers of 1,2,4,5-Tetracyanobenzene with Zigzag Sheet and Porous Frameworks. Inorg Chem 1998; 37:5651-5656. [PMID: 11670714 DOI: 10.1021/ic980427v] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This paper describes two copper(I) supramolecules with the same anion and cation but quite different topologies and properties. The reaction of [Cu(CH(3)CN)(4)]PF(6) and 1,2,4,5-tetracyanobenzene (TCNB) leads to two novel polymeric coordination compounds, [Cu(2)(TCNB)(3)](PF(6))(2)(Me(2)CO)(4)( )()(1) and [Cu(2)(TCNB)(3)](PF(6))(2) (2), depending on the solvents used. The crystal structures have been determined by single-crystal X-ray diffraction. Crystal data are as follows. 1: C(21)H(15)N(6)O(2)CuPF(6), monoclinic, P2(1)/a, a = 11.553(4) Å, b = 16.135(7) Å, c = 15.046(3) Å, beta = 108.08(2) degrees, Z = 4. 2: C(15)H(3)N(6)CuPF(6), orthorhombic, Cmcm, a = 28.282(3) Å, b = 10.337(3) Å, c = 16.285(4) Å, Z = 16. In both polymers, copper(I) ions have similar pseudotetrahedral environments and the four coordination sites are fully occupied by the four bridging ligands, two &mgr;(2)-TCNB and two &mgr;(4)-TCNB groups. Polymer 1, obtained in acetone, revealed a two-dimensional zigzag sheet network between copper(I) ions, whereas 2, synthesized in methylethyl ketone, displayed a three-dimensional porous framework with different functional groups (or atom) in different cavities. The redox, magnetic, and conductive behaviors of both complexes are discussed. It is demonstrated that the two complexes give different physicochemical properties.
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Affiliation(s)
- Megumu Munakata
- Department of Chemistry and Research Institute for Science and Technology, Kinki University, Kowakae, Higashi-Osaka, Osaka 577-8502, Japan
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12
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Adam W, Moorthy JN, Nau WM, Scaiano JC. Photoreduction of Azoalkanes by Direct Hydrogen Abstraction from 1,4-Cyclohexadiene, Alcohols, Stannanes, and Silanes. J Org Chem 1997; 62:8082-8090. [PMID: 11671915 DOI: 10.1021/jo971105w] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A mechanistic investigation of the photoreduction of the n,pi triplet-excited azo chromophore has been carried out on azoalkanes 1, which exhibit efficient intersystem-crossing quantum yields (ca. 0.5). The azoalkanes 1a and 1b undergo facile photoreduction to the corresponding hydrazines in the presence of a variety of hydrogen donors, which include 2-propanol, benzhydrol, 1,4-cyclohexadiene, tributylstannane, and tris(trimethylsilyl)silane. In contrast, the hydrazine yields derived for the azoalkanes 1c and 1d are significantly lower even at high hydrogen donor concentrations due to their lower triplet yields and shorter triplet lifetimes. A clear dependence of the hydrazine yields on the bond dissociation energies of the hydrogen donors has been observed, which is reflected in the quenching rate constants obtained from time-resolved transient absorption spectroscopy. The absolute rate constants for interaction of the triplet azoalkane 1a with hydrogen donors are generally lower (ca. 10-100-fold) than for benzophenone, in line with the less favorable reaction thermodynamics. The comparison of the rate constants for quenching of the triplet-excited azoalkane 1a and of the singlet-excited state of 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) reveals a similar reactivity of excited azoalkanes toward hydrogen donors; differences can be accounted for in terms of variations in the energies of the excited states. The interactions of the excited azoalkanes with tributylstannane and benzhydrol produce the radicals characteristic for hydrogen abstraction from these substrates, namely tributylstannyl and hydroxydiphenylmethyl radicals, which were detected through their transient absorptions at 390 and 550 nm, respectively. Interestingly, compared to the photoreduction of benzophenone with benzhydrol, for which the quantum yield for conversion to radicals is unity, between the azoalkane 1a and benzhydrol this efficiency is only ca. 12%. An associative effect through N.H-O bonding is held responsible, which promotes hydrogen transfer versus diffusion out of the caged radical pair. The quenching of the singlet-excited DBO by toluene was also employed to monitor the formation of benzyl radicals (at 317 nm). The photolysis of DBO in tetrahydrofuran as solvent and quencher produced an absorption at ca. 290 nm, which was tentatively assigned to the corresponding hydrazinyl radical.
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Affiliation(s)
- Waldemar Adam
- Institut für Organische Chemie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany, the Institut für Physikalische Chemie, Universität Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland, and the Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5, Canada
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