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Eames J, Weerasooriya N. Recent Studies on the Regioselective C-Protonation of Enol Derivatives using Carbonyl-Containing Proton Donors. JOURNAL OF CHEMICAL RESEARCH 2019. [DOI: 10.3184/030823401103168154] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Enolate protonation can occur by two different pathways. With strong acids regioselective protonation generally occurs on the oxygen of the enolate to give an enol and then acid catalysed tautomerisation leads directly to the thermody-namically preferred carbonyl motif. However, with much weaker acids kinetic protonation on carbon can occur to give directly the carbonyl derivative. This review discuss recent developments into the use of chelating acids to promote this stereochemically important C-protonation and we comment on factors that appear to promote this selectivity.
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Affiliation(s)
- Jason Eames
- Department of Chemistry, Queen Mary, University of London, Mile End Road, London E1 4NS, UK
| | - Neluka Weerasooriya
- Department of Chemistry, Queen Mary, University of London, Mile End Road, London E1 4NS, UK
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Heß T, Raabe G, Gais HJ. Lithium-Titanium Exchange of Tertiary α-Sulfonyl Carbanions: Synthesis, Structure, Dynamics and Reactivity of Bis(1-sulfonylalkyl)titaniums. European J Org Chem 2014. [DOI: 10.1002/ejoc.201402896] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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3
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Coumbarides GS, Eames J, Suggate MJ, Weerasooriya N. Investigations into theC-deuteriation of aryl alkyl ketones using urea as a pro-base in the presence of a deuterium donor. J Labelled Comp Radiopharm 2006. [DOI: 10.1002/jlcr.1083] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Begum M, Chavda S, Coumbarides GS, Dingan M, Eames J, Suggate MJ, Weerasooriya N. Probing the regioselectiveC-deuteriation of lithium enolates derived from 2-methyl-tetralone in the presence of substituted tertiary amines. J Labelled Comp Radiopharm 2006. [DOI: 10.1002/jlcr.1089] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Coumbarides GS, Eames J, Weerasooriya N. The synthesis and characterisation of multi-labelled [D,13C] 2-deuterio-2-methyl aromatic ketones. J Labelled Comp Radiopharm 2003. [DOI: 10.1002/jlcr.693] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Zimmerman HE, Wang P. Inter- and intramolecular stereoselective protonation of enols(1,2). J Org Chem 2002; 67:9216-26. [PMID: 12492323 DOI: 10.1021/jo026187p] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Kinetic control of the stereoselectivity of protonation of enolates and other delocalized species commonly affords the less stable diastereomer as a consequence of the considerable exothermicity and resulting sp(2) transition-state hybridization of the alpha-carbon. Protonation then is from the less hindered face of the enolate. The present study is aimed at reversing this phenomenon by intramolecular delivery of the proton. The approach employed required the synthesis of two enolate precursors, one with a 2-pyridyl group strategically close to the alpha-carbon and the other with a phenyl group in the same location. The synthesis required 15 steps and involved new methodology. Intramolecular proton transfer, reversing the usual stereoselectivity, was successful. The selectivity proved to depend on several factors including the exo versus endo configuration of the diastereomer reacting, the proton donor employed, and the concentration of the proton donor. A kinetic analysis permitted the determination of the relative reaction orders of the protonation on the two faces of the enolate.
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Affiliation(s)
- Howard E Zimmerman
- Chemistry Department, University of Wisconsin, 1101 University Avenue, Madison, Wisconsin 53706, USA.
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Fleming FF, Wang Q, Zhang Z, Steward OW. Gamma-hydroxy-alpha,beta-alkenenitriles: chelation-controlled conjugate additions. J Org Chem 2002; 67:5953-6. [PMID: 12182627 DOI: 10.1021/jo0258150] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Temporarily anchoring Grignard and organolithium reagents to gamma-hydroxy-alpha,beta-alkenenitriles promotes efficient conjugate additions to what are otherwise recalcitrant Michael acceptors. Sequential deprotonation and addition of a modest excess of a second Grignard reagent allows effective conjugate delivery of alkyl groups to cyclic and acyclic alkenenitriles. Mechanistically, conjugate additions proceed through alkylmagnesium alkoxide complexes for all but the more substituted alkenenitriles that require alkyl transfers from the more reactive ate complexes. Synthetically, chelation-controlled conjugate additions rapidly, and stereoselectively, assemble substituted nitriles, installing up to two new stereocenters in a single synthetic operation.
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Affiliation(s)
- Fraser F Fleming
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282-1530, USA.
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Abstract
[structure: see text] Reversal of the normal kinetic protonation stereochemistry results as a consequence of intramolecular delivery.
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Affiliation(s)
- Howard E Zimmerman
- Chemistry Department, University of Wisconsin, Madison, Wisconsin 53706, USA.
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Coumbarides GS, Eames J, Weerasooriya N. A Succinct Route to the Synthesis of Multi-Labelled [D, 13C] α-Methyl Aromatic Ketones. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2002. [DOI: 10.1246/bcsj.75.1163] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Davies HM, Hodges LM, Gregg TM. Diastereoselective kinetic protonation of exocyclic enolates derived from bicyclic ketones: control of stereochemistry mediated by bridging heteroatoms. J Org Chem 2001; 66:7898-902. [PMID: 11701056 DOI: 10.1021/jo0158940] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- H M Davies
- Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA.
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Coumbarides GS, Eames J, Weerasooriya N. Conformational effects in the diastereoselective protonation of chiral enolates derived from 2,4-dimethyl-1-tetralone using carbonyl chelating proton donors. CAN J CHEM 2000. [DOI: 10.1139/v00-084] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The synthesis of syn-2,4-dimethyl-1-tetralone 6 via a reprotonation strategy using chelating proton donors is discussed. We comment on the comformational effects associated with these acids, and discuss the differences between direct protonation and deprotonation-reprotonation of chiral enolates in the presence of diisopropylamine and LiBr.Key words: conformation, chelating proton donors, deprotonation-reprotonation strategy, diastereoselective protonation and solvent effects.
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Coumbarides GS, Eames J, Weerasooriya N. Investigations into the mechanism of regioselective C-deuteriation of enolates under ‘base-free’ conditions. Tetrahedron Lett 2000. [DOI: 10.1016/s0040-4039(00)00897-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Laval G, Audran G, Galano JM, Monti H. A short and efficient enantiospecific synthesis of (+)-(2R, 6S)-cis-gamma-irone via a highly diastereoselective protonation. J Org Chem 2000; 65:3551-4. [PMID: 10843647 DOI: 10.1021/jo991903h] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- G Laval
- Laboratoire de Réactivité Organique Sélective associé au CNRS Faculté des Sciences de St-Jérôme, Avenue Escadrille Normandie-Niemen, 13397 Marseille Cedex 20, France
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Zimmerman HE, Ignatchenko A. Control of the Stereochemistry of Kinetic Protonation: Intramolecular Proton Delivery(1)(,)(2). J Org Chem 1999; 64:6635-6645. [PMID: 11674666 DOI: 10.1021/jo990323h] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Four decades ago, we noted that for delocalized carbanions and enols the protonation transition state is close to sp(2) hybridized and that, as a consequence, under kinetic control protonation takes place from the less hindered approach, most often with formation of the less stable of two possible stereoisomers. The initial report was followed by an extensive series of examples. Nevertheless, a major question remained, namely whether it was possible to deliver the proton to the more hindered face of such a species using intramolecular proton transfer. To this end, silyl ether precursors to the enols of 3-benzoyl-endo-6-phenyl-exo-6-pyridylbicyclo[3.1.0]hexane and its endo-6-pyridyl-exo-6-phenyl stereoisomer were synthesized. The corresponding enols were generated with fluoride anion. The endo-phenyl enol stereoisomers, on kinetic protonation, led stereoselectively to the endo-3-benzoyl product resulting from the less hindered protonation. In stark contrast, the endo-6-pyridyl enol isomer led stereoselectively to the exo-3-benzoyl ketone by intramolecular proton delivery. However, the kinetic orders of the stereochemistries differ; the intramolecular process requires additional proton donor molecules. The log of the ratio of the two stereochemistries is linear with the log of the proton donor concentration with the slope giving the difference in kinetic orders. An aromatic cyclic 14 electron Hückel transition state is proposed. Additionally, the roles of acyl, nitro and cyano delocalizing groups were analyzed with ab initio computations.
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Diastereoselective protonation of chiral enolates derived from 2,4-dimethyl-1-tetralone using carbonyl chelating proton donors. Tetrahedron Lett 1999. [DOI: 10.1016/s0040-4039(99)01114-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Tanikaga R, Nishikawa T, Tomita N. Stereochemical Behaviors of Cyclohexylα-Sulfonyl Carbanions. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 1999. [DOI: 10.1246/bcsj.72.1057] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Zimmerman HE, Ignatchenko A. Reversal of the Stereochemistry of Kinetic Protonation by Intramolecular Proton Delivery and a Remarkable Dependence of Selectivity on Donor Concentration1. J Am Chem Soc 1998. [DOI: 10.1021/ja9823262] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Töke L, Bakó P, Keser″u GM, Albert M, Fenichel L. Asymmetric Michael addition and deracemization of enolate by chiral crown ether. Tetrahedron 1998. [DOI: 10.1016/s0040-4020(97)10271-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Krause N, Ebert S, Haubrich A. Diastereoselective Protonation of Chiral Enolates with Chelating Proton Donors under Reagent Control: Scope, Mechanism, and Applications. ACTA ACUST UNITED AC 1997. [DOI: 10.1002/jlac.199719971204] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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20
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Mohrig JR, Rosenberg RE, Apostol JW, Bastienaansen M, Evans JW, Franklin SJ, Frisbie CD, Fu SS, Hamm ML, Hirose CB, Hunstad DA, James TL, King RW, Larson CJ, Latham HA, Owen DA, Stein KA, Warnet R. Diastereoselectivity of Enolate Anion Protonation. H/D Exchange of β-Substituted Ethyl Butanoates in Ethanol-d. J Am Chem Soc 1997. [DOI: 10.1021/ja962631s] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jerry R. Mohrig
- Contribution from the Department of Chemistry, Carleton College, Northfield, Minnesota 55057
| | - Robert E. Rosenberg
- Contribution from the Department of Chemistry, Carleton College, Northfield, Minnesota 55057
| | - John W. Apostol
- Contribution from the Department of Chemistry, Carleton College, Northfield, Minnesota 55057
| | - Mark Bastienaansen
- Contribution from the Department of Chemistry, Carleton College, Northfield, Minnesota 55057
| | - Jordan W. Evans
- Contribution from the Department of Chemistry, Carleton College, Northfield, Minnesota 55057
| | - Sonya J. Franklin
- Contribution from the Department of Chemistry, Carleton College, Northfield, Minnesota 55057
| | - C. Daniel Frisbie
- Contribution from the Department of Chemistry, Carleton College, Northfield, Minnesota 55057
| | - Sabrina S. Fu
- Contribution from the Department of Chemistry, Carleton College, Northfield, Minnesota 55057
| | - Michelle L. Hamm
- Contribution from the Department of Chemistry, Carleton College, Northfield, Minnesota 55057
| | - Christopher B. Hirose
- Contribution from the Department of Chemistry, Carleton College, Northfield, Minnesota 55057
| | - David A. Hunstad
- Contribution from the Department of Chemistry, Carleton College, Northfield, Minnesota 55057
| | - Thomas L. James
- Contribution from the Department of Chemistry, Carleton College, Northfield, Minnesota 55057
| | - Randall W. King
- Contribution from the Department of Chemistry, Carleton College, Northfield, Minnesota 55057
| | - Christopher J. Larson
- Contribution from the Department of Chemistry, Carleton College, Northfield, Minnesota 55057
| | - Hallie A. Latham
- Contribution from the Department of Chemistry, Carleton College, Northfield, Minnesota 55057
| | - David A. Owen
- Contribution from the Department of Chemistry, Carleton College, Northfield, Minnesota 55057
| | - Karin A. Stein
- Contribution from the Department of Chemistry, Carleton College, Northfield, Minnesota 55057
| | - Ronald Warnet
- Contribution from the Department of Chemistry, Carleton College, Northfield, Minnesota 55057
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Spence JD, Wyatt JK, Bender DM, Moss DK, Nantz MH. Stereogenic Propargylic Centers via Base-Mediated Terminal Allene Isomerization. J Org Chem 1996; 61:4014-4021. [PMID: 11667276 DOI: 10.1021/jo960276i] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A study of alkali metal amide-mediated isomerizations of terminal allenes is described. The isomerizations of substituted ethenylidenecyclohexanes to form diastereomeric mixtures of terminal alkynes have been conducted to determine factors which may influence the stereochemistry at the newly formed propargylic centers. An initial base screen revealed that potassium N-methylbutylamide (KMBA) exhibits the highest level of equatorial to axial alkyne diastereoselectivity. With the severely hindered terminal allene 26, the use of potassium 3-aminopropylamide is required to effect isomerization. A general synthesis of deuterated terminal allenes has also been achieved, and a mechanistic study using d(2)-allenes 18a,b has revealed the involvement of a propargylic anion in the course of the KMBA-mediated isomerizations.
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Affiliation(s)
- John D. Spence
- Department of Chemistry, University of California-Davis, Davis, California 95616
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Tőke L, Fenichel L, Albert M. Asymmetric Michael reaction. Deracemization of enolate by chiral crown ether. Tetrahedron Lett 1995. [DOI: 10.1016/0040-4039(95)01150-g] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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23
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Kinetic asymmetric protonation as a stereochemistry determining step in theMichael addition of acetic acid derivatives to ?-substituted cinnamic acid derivatives. MONATSHEFTE FUR CHEMIE 1995. [DOI: 10.1007/bf00811020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Gerlach U, Haubenreich T, Hünig S. Enantioselektive Protonierung von Lacton-Enolaten. ACTA ACUST UNITED AC 1994. [DOI: 10.1002/cber.19941271021] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Krause N. Substituenteneffekte und Komplexierungsphänomene bei der diastereoselektiven Protonierung chiraler Enolate. Angew Chem Int Ed Engl 1994. [DOI: 10.1002/ange.19941061724] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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26
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Hünig S, Keita Y, Peters K, von Schnering HG. Stereoselektive Protonierung von Carbanionen, 3. 1,3-Dioxolan-4-one und 1,3-Oxazolidin-4-one: Synthesen und diastereoselektive Protonierung ihrer Anionen. ACTA ACUST UNITED AC 1994. [DOI: 10.1002/cber.19941270824] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Strzalko T, Seyden-Penne J, Wartski L, Froment F, Corset J. Effect of aggregation of nitrile anions on the 1,2 versus 1,4 regioselectivity towards benzylideneacetone. Tetrahedron Lett 1994. [DOI: 10.1016/s0040-4039(00)76706-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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28
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Hünig S, Klaunzer N, Wenner H. Stereoselektive Protonierung von Carbanionen, 2. Diastereoselektive Protonierung von Schöllkopf-Bislactimether-Anionen. ACTA ACUST UNITED AC 1994. [DOI: 10.1002/cber.19941270125] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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29
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Wünsch B, Diekmann H, Höfner G. Homochirale 2,4-disubstituierte 1,3-Dioxane aus (S)-(−)-Äpfelsäure: Stereoselektive Synthese und Untersuchung der NMDA-Rezeptoraffinität aller vier Stereoisomerer. ACTA ACUST UNITED AC 1993. [DOI: 10.1002/jlac.1993199301208] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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