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Lynch DM, Scanlan EM. Thiyl Radicals: Versatile Reactive Intermediates for Cyclization of Unsaturated Substrates. Molecules 2020; 25:E3094. [PMID: 32646036 PMCID: PMC7412111 DOI: 10.3390/molecules25133094] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 06/30/2020] [Accepted: 07/02/2020] [Indexed: 01/11/2023] Open
Abstract
Sulfur centered radicals are widely employed in chemical synthesis, in particular for alkene and alkyne hydrothiolation towards thioether bioconjugates. The steadfast radical chain process that enables efficient hydrothiolation has been explored in the context of cascade reactions to furnish complex molecular architectures. The use of thiyl radicals offers a much cheaper and less toxic alternative to the archetypal organotin-based radical methods. This review outlines the development of thiyl radicals as reactive intermediates for initiating carbocyclization cascades. Key developments in cascade cyclization methodology are presented and applications for natural product synthesis are discussed. The review provides a chronological account of the field, beginning in the early seventies up to very recent examples; a span of almost 50 years.
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Affiliation(s)
| | - Eoin M. Scanlan
- School of Chemistry and Trinity Biomedical Sciences Institute (TBSI), Trinity College Dublin, The University of Dublin, Dublin 2, Ireland;
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Zhang W, Mo JY, He W, Kennepohl P, Sammis GM. Regiocontrolled and Stereoselective Syntheses of Tetrahydrophthalazine Derivatives using Radical Cyclizations. Chemistry 2019; 25:976-980. [PMID: 30350381 DOI: 10.1002/chem.201805249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Indexed: 11/06/2022]
Abstract
Tetrahydrophthalazine derivatives have found important applications in pharmaceutical research, but existing synthetic methods are unable to access them regio- and stereoselectively. Here, a new approach is presented that addresses these challenges by utilizing a 6-endo-trig radical cyclization in the key step. The desired tetrahydrophthalazines can be accessed in high yields (55-98 %) and high diastereoselectivities for the trans-product (>95:5) starting either from readily accessible hydrazones, or from the corresponding aldehydes and substituted Boc-hydrazides in a one-pot process. The synthetic versatility of the tetrahydrophthalazine core was demonstrated by its straightforward conversion to dihydro-phthalazines, phthalazines, or pyrazolo dione derivatives. Furthermore, the N-N bond was reduced to afford a new route to 1,4-diamines.
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Affiliation(s)
- Wei Zhang
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T 1Z1, Canada
| | - Jia Yi Mo
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T 1Z1, Canada
| | - Weiying He
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T 1Z1, Canada
| | - Pierre Kennepohl
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T 1Z1, Canada
| | - Glenn M Sammis
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T 1Z1, Canada
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Affiliation(s)
- Fabrice Dénès
- Laboratoire CEISAM UMR CNRS 6230 - UFR des Sciences et Techniques, Université de Nantes , 2 rue de la Houssinière, BP 92208 - 44322 Nantes Cedex 3, France
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Friestad GK. Control of asymmetry in the radical addition approach to chiral amine synthesis. Top Curr Chem (Cham) 2014; 343:1-32. [PMID: 24085561 PMCID: PMC4114248 DOI: 10.1007/128_2013_481] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The state-of-the-science in asymmetric free radical additions to imino compounds is presented, beginning with an overview of methods involving stereocontrol by various chiral auxiliary approaches. Chiral N-acylhydrazones are discussed with respect to their use as radical acceptors for Mn-mediated intermolecular additions, from design to scope surveys to applications to biologically active targets. A variety of aldehydes and ketones serve as viable precursors for the chiral hydrazones, and a variety of alkyl iodides may be employed as radical precursors, as discussed in a critical review of the functional group compatibility of the reaction. Applications to amino acid and alkaloid synthesis are presented to illustrate the synthetic potential of these versatile stereocontrolled carbon-carbon bond construction reactions. Asymmetric catalysis is discussed, from seminal work on the stereocontrol of radical addition to imino compounds by non-covalent interactions with stoichiometric amounts of catalysts, to more recent examples demonstrating catalyst turnover.
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Ding F, Cai S, William R, Liu XW. Pathways leading to 3-amino- and 3-nitro-2,3-dideoxy sugars: strategies and synthesis. RSC Adv 2013. [DOI: 10.1039/c3ra40595h] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Radical Additions to Chiral Hydrazones: Stereoselectivity and Functional Group Compatibility. Top Curr Chem (Cham) 2011; 320:61-91. [DOI: 10.1007/128_2011_163] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
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Friestad GK, Jiang T, Fioroni GM. Stereocontrol in radical Mannich equivalents for aminosugar synthesis: haloacetal and 2-(phenylthio)vinyl tethered radical additions to α-hydroxyhydrazones. Tetrahedron 2008. [DOI: 10.1016/j.tet.2008.10.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Luft JAR, Winkler T, Kessabi FM, Houk KN. Substituent effects on the rearrangements of cyclohexyl to cyclopentyl radicals involving avermectin-related radicals. J Org Chem 2008; 73:8175-81. [PMID: 18842059 DOI: 10.1021/jo800923a] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The rearrangement of a substituted cyclohexyl radical to a cyclopentylmethyl radical on the skeleton of avermectin B1 has been investigated using density functional (UB3LYP/6-31G(d)) and G3MP2B3 computational methods. The rearrangement is preferred when highly radical stabilizing groups are present at the 2- and 3-positions of the cyclohexyl radical. A substituent on the 3-position of the cyclohexyl radical enables ring-cleavage of the cyclohexyl radical, while a radical stabilizing substituent on the 2-position of the cyclohexyl radical stabilizes the final cyclopentylmethyl radical, enabling the overall rearrangement and reversing the normal thermodynamic preference for the hexenyl radical ring closure.
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Affiliation(s)
- Jennifer A R Luft
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, USA
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Friestad GK, Mathies AK. Effects of alpha-Alkoxy Substitution and Conformational Constraints on 6-exo Radical Cyclizations of Hydrazones via Reversible Thiyl and Stannyl Additions. Tetrahedron 2007; 63:9373-9381. [PMID: 18797497 PMCID: PMC2034276 DOI: 10.1016/j.tet.2007.06.117] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Access to multifunctional hydrazones of relevance to dysiherbaine synthesis studies is described. Subsequent radical cyclizations of multifunctional hydrazones via a Si- and C-linked tethering strategy are shown to function effectively in 6-exo fashion. Conformational constraints are proposed to play a key role in suppressing unproductive premature reduction pathways. The stereochemical outcomes suggest that minimizing the dipole repulsion between neighboring C=N and C-O bonds favors a C(alpha)-C(=N) dihedral angle placing the C=N bond axial within a chairlike transition state, in contrast to the usual Beckwith-Houk model.
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Friestad GK, Jiang T, Mathies AK. Enhanced reactivity in radical cyclizations of hydrazones using the silicon-tethered 1-bromovinyl group. Tetrahedron 2007. [DOI: 10.1016/j.tet.2007.03.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Friestad GK, Jiang T, Mathies AK. Aldehyde-Selective Wacker Oxidation in a Thiyl-Mediated Vinyl Group Transfer Route to Daunosamine. Org Lett 2007; 9:777-80. [PMID: 17284042 DOI: 10.1021/ol063010z] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
[reaction: see text] Asymmetric dihydroxylation, thiyl radical mediated transfer of a silicon-tethered vinyl group to a hydrazone and an unconventional aldehyde-selective Wacker oxidation are sequenced for an efficient synthesis of methyl N-trifluoroacetyl-L-daunosaminide in 32% overall yield from crotonaldehyde.
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Affiliation(s)
- Gregory K Friestad
- Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, USA.
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Zhao CH, Liu L, Chen YJ, Wang D. Synthesis of enatiomerically enriched β-amino alcohol derivatives via chiral base mediated-asymmetric deprotonation of (benzyl methyl ether) tricarbonylchromium(0) complex and electrophilic trapping with imines. JOURNAL OF CHEMICAL RESEARCH 2004. [DOI: 10.3184/0308234042430485] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Deprotonation of (benzyl methyl ether)tricarbonylchromium(0) complex 1 by chiral base 2 followed by quenching reaction with imines 3 and subsequent decomplexation give β-amino alcohol derivatives 5 in good yields and high enantioselectivities (up to 96% e.e.).
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Affiliation(s)
- Cui-Hua Zhao
- Laboratory of Chemical Biology, Center for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100080, P. R. China
| | - Li Liu
- Laboratory of Chemical Biology, Center for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100080, P. R. China
| | - Yong-Jun Chen
- Laboratory of Chemical Biology, Center for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100080, P. R. China
| | - Dong Wang
- Laboratory of Chemical Biology, Center for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100080, P. R. China
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Kimura T, Shoda R, Taniguchi N, Kamikawa K, Uemura M. Asymmetric synthesis of β-amino alcohol by reductive cross-coupling of planar chiral ferrocenecarboxaldehyde with N-tosyl ferrocenylideneamine, and its application to asymmetric reaction. Inorganica Chim Acta 2004. [DOI: 10.1016/j.ica.2003.12.030] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Friestad GK, Jiang T, Mathies AK, Massari SE. SILICON-CONTAINING HETEROCYCLES IN STEREOCONTROLLED RADICAL ADDITIONS TO CHIRAL HYDRAZONES. PHOSPHORUS SULFUR 2004. [DOI: 10.1080/10426500490429022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
| | - Tao Jiang
- a University of Vermont , Burlington, Vermont, USA
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Ding H, Friestad GK. Trifluoroacetyl-Activated Nitrogen−Nitrogen Bond Cleavage of Hydrazines by Samarium(II) Iodide. Org Lett 2004; 6:637-40. [PMID: 14961642 DOI: 10.1021/ol036480r] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
[reaction: see text] Trifluoroacetyl derivatives of hydrazines undergo clean and efficient reductive cleavage of the N-N bond with SmI(2) in the presence of MeOH. After N-trifluoroacetylation, acyl-, aryl-, and alkyl-substituted hydrazines are reductively cleaved by this method to afford trifluoroacetamides in yields ranging from 70 to 96%. These conditions accommodate alkene functionality, avoid racemization, and furnish chiral amines bearing a readily removable TFA protecting group.
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Affiliation(s)
- Hui Ding
- Department of Chemistry, University of Vermont, Burlington, Vermont 05405, USA
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Friestad GK, Massari SE. A Silicon Tether Approach for Addition of Functionalized Radicals to Chiral α-Hydroxyhydrazones: Diastereoselective Additions of Hydroxymethyl and Vinyl Synthons. J Org Chem 2004; 69:863-75. [PMID: 14750816 DOI: 10.1021/jo035405r] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Stereocontrolled additions of hydroxymethyl and vinyl groups to chiral alpha-hydroxyhydrazones can be achieved by radical cyclizations using bromomethyl or vinyl radical precursors tethered via a temporary silicon connection. Tin-mediated 5-exo radical cyclization of alpha-hydroxyhydrazones using a silicon-tethered bromomethyl group, followed by oxidative removal of the tether, provides anti-2-hydrazino 1,3-diols in good yield. Tandem thiyl radical addition-cyclization of alpha-hydroxyhydrazones using a silicon-tethered vinyl group, followed by treatment with potassium fluoride, affords acyclic allylic anti-hydrazino alcohols in good yield. The thiyl addition-cyclization method has been successfully extended to the use of alpha,beta-dihydroxyhydrazones without prior protection or hydroxyl differentiation. Diastereoselection in both reaction types increases with increasing A values of the appended groups, consistent with prediction by the Beckwith-Houk model for stereocontrol in 5-hexenyl radical cyclizations.
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Affiliation(s)
- Gregory K Friestad
- Department of Chemistry, University of Vermont, Burlington, Vermont 05405, USA.
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Tandem thiyl radical addition and cyclization of chiral hydrazones using a silicon-tethered alkyne. ACTA ACUST UNITED AC 2003. [DOI: 10.1016/s0957-4166(03)00540-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Abstract
[reaction: see text] Temporary union of alkynes in the Fe(CO)5-promoted cyclocarbonylation provides a method for carbonylative cross-coupling of alkynes to construct unsymmetrically substituted cyclopentadienones.
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Affiliation(s)
- Anthony J Pearson
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, USA.
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Lukevics E, Abele E. Recent Advances in the Synthesis and Transformations of Heterocycles Mediated by Fluoride Ion Activated Organosilicon Compounds. HETEROCYCLES 2002. [DOI: 10.3987/rev-01-545] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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