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== Structure ==
== Structure ==


Montréalones are a class of [[Saturated and unsaturated compounds|unsaturated]] 5-membered [[wikt: organophosphorus|organophosphorus]] heterocycle incorporating, within their ring system, overlapping [[azomethine ylide]] and [[Wittig reaction#Wittig reagents|Wittig-type]] moieties.<ref>Reissig, H.-U.; Zimmer, R., Münchnones—New Facets after 50 Years. ''Angew. Chem. Int. Edit.'' '''2014''', ''53'', 9708. ({{DOI|10.1002/anie.201405092}})</ref><ref name ="St-Cyr2007">St. Cyr, D. J.; Arndtsen, B. A., A New Use of Wittig-type Reagents as 1,3-Dipolar Cycloaddition Precursors and in [[Pyrrole]] Synthesis. ''J. Am. Chem. Soc.'' '''2007''', ''129'', 12366. ({{DOI|10.1021/ja074330w}})</ref> Depending on the phosphorus substituents, ring-chain [[Tautomer#Valence tautomerism|valence tautomerism]] allows montréalones to display variable degrees of equilibrium and structural blending with ''N''-acylamino [[Ylide#Phosphonium_ylides| phosphonium ylide]] forms.<ref>Krenske, E. H.; Houk, K. N.; Arndtsen, B. A.; St. Cyr, D. J., Cyclic 1,3-Dipoles or Acyclic Phosphonium Ylides? Electronic Characterization of "Montréalones". ''J. Am. Chem. Soc.'' '''2008''', ''130'', 10052. ({{DOI|10.1021/ja802646f}})</ref> Electron rich phenyl groups favor the acyclic [[Ylide#Phosphonium_ylides|ylide]] form whereas electron poor [[Alkoxy group|aryloxy]] groups favor the heterocyclic form. requiring the use of [[Phosphite#Synthesis_of_phosphite_esters|phosphites]] and [[phosphonite]]s as [[Organophosphorus_compound#Organophosphorus.28III.29_compounds.2C_main_categories |organophosphorus(III) precursor]] in order to obtain the [[1,3-dipole]].
Montréalones are a class of [[Saturated and unsaturated compounds|unsaturated]] 5-membered [[wikt: organophosphorus|organophosphorus]] heterocycle incorporating, within their ring system, overlapping [[azomethine ylide]] and [[Wittig reaction#Wittig reagents|Wittig-type]] moieties.<ref>Reissig, H.-U.; Zimmer, R., Münchnones—New Facets after 50 Years. ''Angew. Chem. Int. Edit.'' '''2014''', ''53'', 9708. ({{DOI|10.1002/anie.201405092}})</ref><ref name ="St-Cyr2007">St. Cyr, D. J.; Arndtsen, B. A., A New Use of Wittig-type Reagents as 1,3-Dipolar Cycloaddition Precursors and in [[Pyrrole]] Synthesis. ''J. Am. Chem. Soc.'' '''2007''', ''129'', 12366. ({{DOI|10.1021/ja074330w}})</ref> Depending on the phosphorus substituents, [[Tautomer#Valence tautomerism|ring-chain valence tautomerism]] allows montréalones to display variable degrees of equilibrium and structural blending with ''N''-acylamino [[Ylide#Phosphonium_ylides| phosphonium ylide]] forms.<ref>Krenske, E. H.; Houk, K. N.; Arndtsen, B. A.; St. Cyr, D. J., Cyclic 1,3-Dipoles or Acyclic Phosphonium Ylides? Electronic Characterization of "Montréalones". ''J. Am. Chem. Soc.'' '''2008''', ''130'', 10052. ({{DOI|10.1021/ja802646f}})</ref> Electron rich phenyl groups favor the acyclic [[Ylide#Phosphonium_ylides|ylide]] form whereas electron poor [[Alkoxy group|aryloxy]] groups favor the heterocyclic form. requiring the use of [[Phosphite#Synthesis_of_phosphite_esters|phosphites]] and [[phosphonite]]s as [[Organophosphorus_compound#Organophosphorus.28III.29_compounds.2C_main_categories |organophosphorus(III) precursor]] in order to obtain the [[1,3-dipole]].


[[File:Montrealone resonance and equilibrium structures.png|640x351 px|center]]
[[File:Montrealone resonance and equilibrium structures.png|640x351 px|center]]
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Montréalones are efficient [[1,3-dipolar cycloaddition]] reagents in [[One-pot synthesis|one-pot reactions]] involving [[wikt:dipolarophile|dipolarophiles]] such as [[imine]]s, [[alkene]]s, and [[alkyne]]s to respectively afford [[imidazole]]s,<ref>Aly, S.; Romashko, M.; Arndtsen, B. A., Multicomponent Synthesis of Substituted and Fused-Ring Imidazoles via Phospha-münchnone Cycloaddition. ''J. Org. Chem.'' '''2015''', ''80'', 2709. ({{DOI|10.1021/jo5028936}})</ref> 2-[[pyrroline]]s,<ref>Morin, M. S. T.; Arndtsen, B. A., Chiral Phosphorus-Based 1,3-Dipoles: A Modular Approach to Enantioselective 1,3-Dipolar Cycloaddition and Polycyclic 2-Pyrroline Synthesis. ''Org. Lett.'' '''2014''', ''16'', 1056. ({{DOI|10.1021/ol4035512}})</ref> and [[pyrrole]]s.<ref>St-Cyr, D. J.; Morin, M. S. T.; Belanger-Gariepy, F.; Arndtsen, B. A.; Krenske, E. H.; Houk, K. N., Phospha-Münchnones: Electronic Structures and 1,3-Dipolar Cycloadditions. ''J. Org. Chem.'' '''2010''', ''75'', 4261. ({{DOI|10.1021/jo1008383}})</ref>
Montréalones are efficient [[1,3-dipolar cycloaddition]] reagents in [[One-pot synthesis|one-pot reactions]] involving [[wikt:dipolarophile|dipolarophiles]] such as [[imine]]s, [[alkene]]s, and [[alkyne]]s to respectively afford [[imidazole]]s,<ref>Aly, S.; Romashko, M.; Arndtsen, B. A., Multicomponent Synthesis of Substituted and Fused-Ring Imidazoles via Phospha-münchnone Cycloaddition. ''J. Org. Chem.'' '''2015''', ''80'', 2709. ({{DOI|10.1021/jo5028936}})</ref> 2-[[pyrroline]]s,<ref>Morin, M. S. T.; Arndtsen, B. A., Chiral Phosphorus-Based 1,3-Dipoles: A Modular Approach to Enantioselective 1,3-Dipolar Cycloaddition and Polycyclic 2-Pyrroline Synthesis. ''Org. Lett.'' '''2014''', ''16'', 1056. ({{DOI|10.1021/ol4035512}})</ref> and [[pyrrole]]s.<ref>St-Cyr, D. J.; Morin, M. S. T.; Belanger-Gariepy, F.; Arndtsen, B. A.; Krenske, E. H.; Houk, K. N., Phospha-Münchnones: Electronic Structures and 1,3-Dipolar Cycloadditions. ''J. Org. Chem.'' '''2010''', ''75'', 4261. ({{DOI|10.1021/jo1008383}})</ref>


Cycloaddition reactions of asymmetric [[1,3-dipole]]s and dipolarophiles can lead to [[isomer]]ic product mixtures, particularly with münchnones and alkynes in the synthesis of pyrroles.<ref>Lubell, W.; St-Cyr, D.; Dufour-Gallant, J.; Hopewell, R.; Boutard, N.; Kassem, T.; Dörr, A.; Zelli, R., {{cite web |url= https://www.thieme.de/en/thieme-chemistry/sos-knowledge-updates-2013-58727.htm |title= 1H-Pyrroles (Update 2013)}} ''Science of Synthesis'' '''2013''', ''2013/1'', 157-388.</ref><ref>Gribble, G. W. In ''Oxazoles: Synthesis, Reactions, and Spectroscopy'', A; Palmer, D. C., Ed.; Wiley: New York, 2003; Vol. 60. ({{DOI|10.1002/0471428035.ch4}})</ref><ref>Gingrich, H. L.; Baum, J. S. In ''Oxazoles, Chemistry of Heterocyclic Compounds''; Turchi, I. J., Ed.; Wiley: New York, 1986; Vol. 45. ({{DOI|10.1002/9780470187289.ch4}})</ref> In contrast to related [[Diels-Alder reactions]], rationalization of [[wikt:regioisomeric|regioisomeric]] bias using conventional [[Diels–Alder_reaction#Regioselectivity|frontier molecular orbital]] (FMO) theory fails. The complimentary use of montéalones and münchnones allows product mixtures to be avoided and highlights the need to include reactant geometrical changes in the rationalization process.<ref>Morin, M. S. T.; St-Cyr, D. J.; Arndtsen, B. A.; Krenske, E. H.; Houk, K. N., Modular Mesoionics: Understanding and Controlling Regioselectivity in 1,3-Dipolar Cycloadditions of Münchnone Derivatives. ''J. Am. Chem. Soc.'' '''2013''', ''135'', 17349. ({{DOI|10.1021/ja406833q}})</ref>
Cycloaddition reactions of asymmetric [[1,3-dipole]]s and dipolarophiles can lead to [[isomer]]ic product mixtures, particularly with münchnones and alkynes in the synthesis of pyrroles.<ref>Lubell, W.; St-Cyr, D.; Dufour-Gallant, J.; Hopewell, R.; Boutard, N.; Kassem, T.; Dörr, A.; Zelli, R., {{cite web |url= https://www.thieme.de/en/thieme-chemistry/sos-knowledge-updates-2013-58727.htm |title= 1H-Pyrroles (Update 2013)}} ''Science of Synthesis'' '''2013''', ''2013/1'', 157-388.</ref><ref>Gribble, G. W. In ''Oxazoles: Synthesis, Reactions, and Spectroscopy'', A; Palmer, D. C., Ed.; Wiley: New York, 2003; Vol. 60. ({{DOI|10.1002/0471428035.ch4}})</ref><ref>Gingrich, H. L.; Baum, J. S. In ''Oxazoles, Chemistry of Heterocyclic Compounds''; Turchi, I. J., Ed.; Wiley: New York, 1986; Vol. 45. ({{DOI|10.1002/9780470187289.ch4}})</ref> In contrast to related [[Diels-Alder reactions]], rationalization of [[wikt:regioisomeric|regioisomeric]] bias using conventional [[Diels–Alder_reaction#Regioselectivity|frontier molecular orbital (FMO) theory]] fails. The complimentary use of montéalones and münchnones allows product mixtures to be avoided and highlights the need to consider [[Transition state|transition-state]] geometrical changes (distortion) in the rationalization process.<ref>Morin, M. S. T.; St-Cyr, D. J.; Arndtsen, B. A.; Krenske, E. H.; Houk, K. N., Modular Mesoionics: Understanding and Controlling Regioselectivity in 1,3-Dipolar Cycloadditions of Münchnone Derivatives. ''J. Am. Chem. Soc.'' '''2013''', ''135'', 17349. ({{DOI|10.1021/ja406833q}})</ref>


[[File:Montrealone vs munchnone cycloaddition.png|1024x460 px|center]]
[[File:Montrealone vs munchnone cycloaddition.png|1024x460 px|center]]

Revision as of 17:23, 24 March 2015

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Montréalones (synonym : phospha-münchnones) are mesoionic heterocyclic chemical compounds.

chemical structure of montéalones

Structure

Montréalones are a class of unsaturated 5-membered organophosphorus heterocycle incorporating, within their ring system, overlapping azomethine ylide and Wittig-type moieties.[1][2] Depending on the phosphorus substituents, ring-chain valence tautomerism allows montréalones to display variable degrees of equilibrium and structural blending with N-acylamino phosphonium ylide forms.[3] Electron rich phenyl groups favor the acyclic ylide form whereas electron poor aryloxy groups favor the heterocyclic form. requiring the use of phosphites and phosphonites as organophosphorus(III) precursor in order to obtain the 1,3-dipole.

Synthesis

Montréalones represent a special case of Wittig reagents and are generated in an analogous manner. Reaction of organophosphorus(III) compounds with N-acyliminium ions affords phosphonium salt intermediates which are deprotonated using non-nucleophilic bases (e.g. DBU, LiHMDS). As the N-acyliminium ions are generated in situ from imines and acid chlorides, dipole generation is a multicomponent process. The optimal phosphorus(III) reagent is PhP(catechyl) owing to the nucleophilicity/electrophilicity balance it affords.[2]

Reactions

Montréalones are efficient 1,3-dipolar cycloaddition reagents in one-pot reactions involving dipolarophiles such as imines, alkenes, and alkynes to respectively afford imidazoles,[4] 2-pyrrolines,[5] and pyrroles.[6]

Cycloaddition reactions of asymmetric 1,3-dipoles and dipolarophiles can lead to isomeric product mixtures, particularly with münchnones and alkynes in the synthesis of pyrroles.[7][8][9] In contrast to related Diels-Alder reactions, rationalization of regioisomeric bias using conventional frontier molecular orbital (FMO) theory fails. The complimentary use of montéalones and münchnones allows product mixtures to be avoided and highlights the need to consider transition-state geometrical changes (distortion) in the rationalization process.[10]


See also

References

  1. ^ Reissig, H.-U.; Zimmer, R., Münchnones—New Facets after 50 Years. Angew. Chem. Int. Edit. 2014, 53, 9708. (doi:10.1002/anie.201405092)
  2. ^ a b St. Cyr, D. J.; Arndtsen, B. A., A New Use of Wittig-type Reagents as 1,3-Dipolar Cycloaddition Precursors and in Pyrrole Synthesis. J. Am. Chem. Soc. 2007, 129, 12366. (doi:10.1021/ja074330w)
  3. ^ Krenske, E. H.; Houk, K. N.; Arndtsen, B. A.; St. Cyr, D. J., Cyclic 1,3-Dipoles or Acyclic Phosphonium Ylides? Electronic Characterization of "Montréalones". J. Am. Chem. Soc. 2008, 130, 10052. (doi:10.1021/ja802646f)
  4. ^ Aly, S.; Romashko, M.; Arndtsen, B. A., Multicomponent Synthesis of Substituted and Fused-Ring Imidazoles via Phospha-münchnone Cycloaddition. J. Org. Chem. 2015, 80, 2709. (doi:10.1021/jo5028936)
  5. ^ Morin, M. S. T.; Arndtsen, B. A., Chiral Phosphorus-Based 1,3-Dipoles: A Modular Approach to Enantioselective 1,3-Dipolar Cycloaddition and Polycyclic 2-Pyrroline Synthesis. Org. Lett. 2014, 16, 1056. (doi:10.1021/ol4035512)
  6. ^ St-Cyr, D. J.; Morin, M. S. T.; Belanger-Gariepy, F.; Arndtsen, B. A.; Krenske, E. H.; Houk, K. N., Phospha-Münchnones: Electronic Structures and 1,3-Dipolar Cycloadditions. J. Org. Chem. 2010, 75, 4261. (doi:10.1021/jo1008383)
  7. ^ Lubell, W.; St-Cyr, D.; Dufour-Gallant, J.; Hopewell, R.; Boutard, N.; Kassem, T.; Dörr, A.; Zelli, R., "1H-Pyrroles (Update 2013)". Science of Synthesis 2013, 2013/1, 157-388.
  8. ^ Gribble, G. W. In Oxazoles: Synthesis, Reactions, and Spectroscopy, A; Palmer, D. C., Ed.; Wiley: New York, 2003; Vol. 60. (doi:10.1002/0471428035.ch4)
  9. ^ Gingrich, H. L.; Baum, J. S. In Oxazoles, Chemistry of Heterocyclic Compounds; Turchi, I. J., Ed.; Wiley: New York, 1986; Vol. 45. (doi:10.1002/9780470187289.ch4)
  10. ^ Morin, M. S. T.; St-Cyr, D. J.; Arndtsen, B. A.; Krenske, E. H.; Houk, K. N., Modular Mesoionics: Understanding and Controlling Regioselectivity in 1,3-Dipolar Cycloadditions of Münchnone Derivatives. J. Am. Chem. Soc. 2013, 135, 17349. (doi:10.1021/ja406833q)
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