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Amidine

January 01, 1970

Amidines are organic compounds with the functional group RC(NR)NR2, where the R groups can be the same or different. They are the imine derivatives of amides (RC(O)NR2). The simplest amidine is formamidine, HC(=NH)NH2.

The skeletal formula of acetamidine (acetimidamide).

Examples of amidines include:

Preparation edit

A common route to primary amidines is the Pinner reaction. Reaction of the nitrile with alcohol in the presence of acid gives an iminoether. Treatment of the resulting compound with ammonia then completes the conversion to the amidine.[1] Instead of using a Bronsted acid, Lewis acids such as aluminium trichloride promote the direct amination of nitriles.[2] They are also generated by amination of an imidoyl chloride.[3] They are also prepared by the addition of organolithium reagents to diimines, followed by protonation or alkylation.

Dimethylformamide acetal reacts with primary amines to give amidines:[4]

Me2NC(H)(OMe)2 + RNH2 → Me2NC=NHR + 2 MeOH

Acid-base chemistry edit

Amidines are much more basic than amides and are among the strongest uncharged/unionized bases.[5][6]

Protonation occurs at the sp2-hybridized nitrogen. This occurs because the positive charge can be delocalized onto both nitrogen atoms. The resulting cationic species is known as an amidinium ion[7] and possesses identical C-N bond lengths.

 

Applications edit

Several drug or drug candidates feature amidine substituents. Examples include the antiprotozoal Imidocarb, the insecticide amitraz , the anthelmintic tribendimidine, and xylamidine, an antagonist at the 5HT2A receptor.[8]

Formamidinium (see below) may be reacted with a metal halide to form the light-absorbing semiconducting material in perovskite solar cells. Formamidinium (FA) cations or halides may partially or fully replace methylammonium halides in forming perovskite absorber layers in photovoltaic devices.

Nomenclature edit

Formally, amidines are a class of oxoacids. The oxoacid from which an amidine is derived must be of the form RnE(=O)OH, where R is a substituent. The −OH group is replaced by an −NH2 group and the =O group is replaced by =NR, giving amidines the general structure RnE(=NR)NR2.[9][10][11] When the parent oxoacid is a carboxylic acid, the resulting amidine is a carboxamidine or carboximidamide (IUPAC name). Carboxamidines are frequently referred to simply as amidines, as they are the most commonly encountered type of amidine in organic chemistry.

Derivatives edit

Formamidinium cations edit

 
general structure of a formamidinium cation

A notable subclass of amidinium ions are the formamidinium cations; which can be represented by the chemical formula [R
2N−CH=NR
2]+
. Deprotonation of these gives stable carbenes which can be represented by the chemical formula R
2N−C:−NR
2.[12][13]

Amidinate salts edit

 
Structure of cyclopentadienyl dimethyl zirconium (diisopropyl acetamidinate).[14]

An amidinate salt has the general structure M+[RNRCNR]− and can be accessed by reaction of a carbodiimide with an organometallic compound such as methyl lithium.[15] They are used widely as ligands in organometallic complexes.

See also edit

  • Guanidines — a similar group of compounds where the central carbon atom is bonded to three nitrogen atoms.
  • Imidazolines contain a cyclic amidine.

References edit

  1. ^ A. W. Dox (1928). "Acetamidine Hydrochloride". Organic Syntheses. 8: 1. doi:10.15227/orgsyn.008.0001.
  2. ^ "N-Phenylbenzamidine". Organic Syntheses. 36: 64. 1956. doi:10.15227/orgsyn.036.0064.
  3. ^ Arthur C. Hontz, E. C. Wagner (1951). "N,N-Diphenylbenzamidine". Organic Syntheses. 31: 48. doi:10.15227/orgsyn.031.0048.
  4. ^ Daniel A. Dickman; Michael Boes; Albert I. Meyers (1989). "(S)-N,N-Dimethyl-N'-(1-tert-Butoxy-3-Methyl-2-Butyl)formamidine". Organic Syntheses. 67: 52. doi:10.15227/orgsyn.067.0052.
  5. ^ Roche VF. Improving Pharmacy Students’ Understanding and Long-term Retention of Acid-Base Chemistry. American Journal of Pharmaceutical Education. 2007;71(6):122.
  6. ^ Clayden; Greeves; Warren (2001). Organic chemistry. Oxford university press. p. 202. ISBN 978-0-19-850346-0.
  7. ^ Schrader, Thomas; Hamilton, Andrew D., eds. (2005). Functional synthetic receptors. Wiley-VCH. p. 132. ISBN 3-527-30655-2.
  8. ^ Greenhill, John V.; Lue, Ping (1993). 5 Amidines and Guanidines in Medicinal Chemistry. Progress in Medicinal Chemistry. Vol. 30. pp. 203–326. doi:10.1016/S0079-6468(08)70378-3. ISBN 9780444899897. PMID 7905649.
  9. ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "amidines". doi:10.1351/goldbook.A00267
  10. ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "carboxamidines". doi:10.1351/goldbook.C00851
  11. ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "sulfinamidines". doi:10.1351/goldbook.S06107
  12. ^ Alder, Roger W.; Blake, Michael E.; Bufali, Simone; Butts, Craig P.; Orpen, A. Guy; Schütz, Jan; Williams, Stuart J. (2001). "Preparation of tetraalkylformamidinium salts and related species as precursors to stable carbenes". Journal of the Chemical Society, Perkin Transactions 1 (14): 1586–1593. doi:10.1039/B104110J.
  13. ^ Edward C. Taylor; Wendell A. Ehrhart; M. Kawanisi (1966). "Formamidine Acetate". Organic Syntheses. 46: 39. doi:10.15227/orgsyn.046.0039.
  14. ^ Keaton, Richard J.; Jayaratne, Kumudini C.; Henningsen, David A.; Koterwas, Lisa A.; Sita, Lawrence R. (2001). "Dramatic Enhancement of Activities for Living Ziegler−Natta Polymerizations Mediated by "Exposed" Zirconium Acetamidinate Initiators: The Isospecific Living Polymerization of Vinylcyclohexane". Journal of the American Chemical Society. 123 (25): 6197–6198. doi:10.1021/ja0057326. PMID 11414862.
  15. ^ Ulrich, Henri (2007). Chemistry and technology of carbodiimides. Chichester, England: John Wiley & Sons. ISBN 9780470065105.

January 01, 1970
amidine, organic, compounds, with, functional, group, where, groups, same, different, they, imine, derivatives, amides, simplest, amidine, formamidine, skeletal, formula, acetamidine, acetimidamide, examples, amidines, include, diminazene, benzamidine, pentami. Amidines are organic compounds with the functional group RC NR NR2 where the R groups can be the same or different They are the imine derivatives of amides RC O NR2 The simplest amidine is formamidine HC NH NH2 The skeletal formula of acetamidine acetimidamide Examples of amidines include DBU diminazene benzamidine Pentamidine Paranyline Contents 1 Preparation 2 Acid base chemistry 3 Applications 4 Nomenclature 5 Derivatives 5 1 Formamidinium cations 5 2 Amidinate salts 6 See also 7 ReferencesPreparation editA common route to primary amidines is the Pinner reaction Reaction of the nitrile with alcohol in the presence of acid gives an iminoether Treatment of the resulting compound with ammonia then completes the conversion to the amidine 1 Instead of using a Bronsted acid Lewis acids such as aluminium trichloride promote the direct amination of nitriles 2 They are also generated by amination of an imidoyl chloride 3 They are also prepared by the addition of organolithium reagents to diimines followed by protonation or alkylation Dimethylformamide acetal reacts with primary amines to give amidines 4 Me2NC H OMe 2 RNH2 Me2NC NHR 2 MeOHAcid base chemistry editAmidines are much more basic than amides and are among the strongest uncharged unionized bases 5 6 Protonation occurs at the sp2 hybridized nitrogen This occurs because the positive charge can be delocalized onto both nitrogen atoms The resulting cationic species is known as an amidinium ion 7 and possesses identical C N bond lengths nbsp Applications editSeveral drug or drug candidates feature amidine substituents Examples include the antiprotozoal Imidocarb the insecticide amitraz the anthelmintic tribendimidine and xylamidine an antagonist at the 5HT2A receptor 8 Formamidinium see below may be reacted with a metal halide to form the light absorbing semiconducting material in perovskite solar cells Formamidinium FA cations or halides may partially or fully replace methylammonium halides in forming perovskite absorber layers in photovoltaic devices Nomenclature editFormally amidines are a class of oxoacids The oxoacid from which an amidine is derived must be of the form RnE O OH where R is a substituent The OH group is replaced by an NH2 group and the O group is replaced by NR giving amidines the general structure RnE NR NR2 9 10 11 When the parent oxoacid is a carboxylic acid the resulting amidine is a carboxamidine or carboximidamide IUPAC name Carboxamidines are frequently referred to simply as amidines as they are the most commonly encountered type of amidine in organic chemistry Derivatives editFormamidinium cations edit nbsp general structure of a formamidinium cation A notable subclass of amidinium ions are the formamidinium cations which can be represented by the chemical formula R2 N CH NR2 Deprotonation of these gives stable carbenes which can be represented by the chemical formula R2 N C NR2 12 13 Amidinate salts edit nbsp Structure of cyclopentadienyl dimethyl zirconium diisopropyl acetamidinate 14 An amidinate salt has the general structure M RNRCNR and can be accessed by reaction of a carbodiimide with an organometallic compound such as methyl lithium 15 They are used widely as ligands in organometallic complexes See also editGuanidines a similar group of compounds where the central carbon atom is bonded to three nitrogen atoms Imidazolines contain a cyclic amidine References edit A W Dox 1928 Acetamidine Hydrochloride Organic Syntheses 8 1 doi 10 15227 orgsyn 008 0001 N Phenylbenzamidine Organic Syntheses 36 64 1956 doi 10 15227 orgsyn 036 0064 Arthur C Hontz E C Wagner 1951 N N Diphenylbenzamidine Organic Syntheses 31 48 doi 10 15227 orgsyn 031 0048 Daniel A Dickman Michael Boes Albert I Meyers 1989 S N N Dimethyl N 1 tert Butoxy 3 Methyl 2 Butyl formamidine Organic Syntheses 67 52 doi 10 15227 orgsyn 067 0052 Roche VF Improving Pharmacy Students Understanding and Long term Retention of Acid Base Chemistry American Journal of Pharmaceutical Education 2007 71 6 122 Clayden Greeves Warren 2001 Organic chemistry Oxford university press p 202 ISBN 978 0 19 850346 0 Schrader Thomas Hamilton Andrew D eds 2005 Functional synthetic receptors Wiley VCH p 132 ISBN 3 527 30655 2 Greenhill John V Lue Ping 1993 5 Amidines and Guanidines in Medicinal Chemistry Progress in Medicinal Chemistry Vol 30 pp 203 326 doi 10 1016 S0079 6468 08 70378 3 ISBN 9780444899897 PMID 7905649 IUPAC Compendium of Chemical Terminology 2nd ed the Gold Book 1997 Online corrected version 2006 amidines doi 10 1351 goldbook A00267 IUPAC Compendium of Chemical Terminology 2nd ed the Gold Book 1997 Online corrected version 2006 carboxamidines doi 10 1351 goldbook C00851 IUPAC Compendium of Chemical Terminology 2nd ed the Gold Book 1997 Online corrected version 2006 sulfinamidines doi 10 1351 goldbook S06107 Alder Roger W Blake Michael E Bufali Simone Butts Craig P Orpen A Guy Schutz Jan Williams Stuart J 2001 Preparation of tetraalkylformamidinium salts and related species as precursors to stable carbenes Journal of the Chemical Society Perkin Transactions 1 14 1586 1593 doi 10 1039 B104110J Edward C Taylor Wendell A Ehrhart M Kawanisi 1966 Formamidine Acetate Organic Syntheses 46 39 doi 10 15227 orgsyn 046 0039 Keaton Richard J Jayaratne Kumudini C Henningsen David A Koterwas Lisa A Sita Lawrence R 2001 Dramatic Enhancement of Activities for Living Ziegler Natta Polymerizations Mediated by Exposed Zirconium Acetamidinate Initiators The Isospecific Living Polymerization of Vinylcyclohexane Journal of the American Chemical Society 123 25 6197 6198 doi 10 1021 ja0057326 PMID 11414862 Ulrich Henri 2007 Chemistry and technology of carbodiimides Chichester England John Wiley amp Sons ISBN 9780470065105 Retrieved from https en wikipedia org w index php title Amidine amp oldid 1181686966, wikipedia, wiki, book, books, library,

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