Diazo: Difference between revisions
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{{for|a discussion of copiers using the diazo process|Whiteprint}} |
{{for|a discussion of copiers using the diazo process|Whiteprint}} |
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[[Image:DiazoResonance.svg|300px|right|Diazo]]'''Diazo''' refers to a type of [[organic compound]] that has two linked nitrogen (azo) compounds. The general formula is R<sub>2</sub>C=N<sub>2</sub>. The simplest example of a diazo compound is [[diazomethane]]. The electronic structure of diazo compounds involves a positive charge on the central nitrogen and negative charge distributed between the terminal nitrogen and the carbon. Some of the most stable diazo compounds are α-diazoketones and α-diazoesters since the negative charge is delocalized into the carbonyl. In contrast, most alkyldiazo compounds are explosive. A commercially relevant diazocompound is '''Ethyl diazoacetate''' N<sub>2</sub>CHCOOEt. A group of isomeric compounds with similar properties are the [[diazirine]]s, where the carbon and two nitrogens are linked as a ring. |
[[Image:DiazoResonance.svg|300px|right|Diazo]]'''Diazo''' refers to a type of [[organic compound]] that has two linked nitrogen (azo) compounds. The general formula is R<sub>2</sub>C=N<sub>2</sub>. The simplest example of a diazo compound is [[diazomethane]]. The electronic structure of diazo compounds involves a positive charge on the central nitrogen and negative charge distributed between the terminal nitrogen and the carbon. Some of the most stable diazo compounds are α-diazoketones and α-diazoesters since the negative charge is delocalized into the carbonyl. In contrast, most alkyldiazo compounds are explosive. A commercially relevant diazocompound is '''Ethyl diazoacetate''' N<sub>2</sub>CHCOOEt. A group of isomeric compounds with similar properties are the [[diazirine]]s, where the carbon and two nitrogens are linked as a ring. |
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A total of 4 [[resonance structures]] can be drawn <ref>F.A. Carey R.J. Sundberg ''Advanced Organic Chemistry'', 2nd Edition</ref>: |
A total of 4 [[resonance structures]] can be drawn <ref>F.A. Carey R.J. Sundberg ''Advanced Organic Chemistry'', 2nd Edition</ref>: |
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:[[Image:Diazo resonance structures.svg|Diazo resonance structures]] |
:[[Image:Diazo resonance structures.svg|Diazo resonance structures]] |
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Diazo compounds should not be confused with [[azo compound]]s of the type R-N=N-R or with [[diazonium compound]]s of the type R-N<sub>2</sub><sup>+</sup>. |
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==Diazo synthesis== |
==Diazo synthesis== |
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Several laboratory methods exist for the preparation of diazo compounds |
Several laboratory methods exist for the preparation of diazo compounds <ref>{{JerryMarch}}</ref>: |
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* Reaction of an [[acyl halide]] with [[diazomethane]], for example the first step in the [[Arndt-Eistert synthesis]] |
* Reaction of an [[acyl halide]] with [[diazomethane]] <ref>Example [[Organic Syntheses]], Coll. Vol. 3, p.119 (1955); Vol. 26, p.13 (1946).[http://www.orgsynth.org/orgsyn/pdfs/CV3P0119.pdf Link]</ref>, for example the first step in the [[Arndt-Eistert synthesis]] |
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* In '''diazo transfer''' certain [[carbon acid]]s can be reacted with [[tosyl azide]] |
* In '''diazo transfer''' certain [[carbon acid]]s can be reacted with [[tosyl azide]] |
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:[[Image:Preparation of diazomalonic acid ester by Dimroth.svg|500px|Preparation of diazomalonic acid ester by Dimroth]] |
:[[Image:Preparation of diazomalonic acid ester by Dimroth.svg|500px|Preparation of diazomalonic acid ester by Dimroth]] |
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:This reaction is also called the '''Regitz diazo transfer''' <ref>M. Regitz, Angew. Chem., 79, 786 (1967); Angew. Chem. Intern. Ed. Engl., 6, 733 (1967).</ref>. Examples are the synthesis of ''tert-butyl diazoaceate '' <ref>Organic Syntheses, Coll. Vol. 5, p.179 (1973); Vol. 48, p.36 (1968). [http://www.orgsyn.org/orgsyn/prep.asp?prep=cv5p0179 Link]</ref> and ''di-tert-butyl diazomalonate'' <ref>Organic Syntheses, Coll. Vol. 6, p.414 (1988); Vol. 59, p.66 (1979). [http://www.orgsyn.org/orgsyn/prep.asp?prep=cv6p0414 Link]</ref> |
:This reaction is also called the '''Regitz diazo transfer''' <ref>M. Regitz, Angew. Chem., 79, 786 (1967); Angew. Chem. Intern. Ed. Engl., 6, 733 (1967).</ref>. Examples are the synthesis of ''tert-butyl diazoaceate '' <ref>Organic Syntheses, Coll. Vol. 5, p.179 (1973); Vol. 48, p.36 (1968). [http://www.orgsyn.org/orgsyn/prep.asp?prep=cv5p0179 Link]</ref> and ''di-tert-butyl diazomalonate'' <ref>Organic Syntheses, Coll. Vol. 6, p.414 (1988); Vol. 59, p.66 (1979). [http://www.orgsyn.org/orgsyn/prep.asp?prep=cv6p0414 Link]</ref> |
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* [[Elimination reaction]] of N-alkyl-N-nitroso compounds <ref>Example: Organic Syntheses, Coll. Vol. 6, p.981 (1988); Vol. 57, p.95 (1977). [http://www.orgsynth.org/orgsyn/pdfs/CV6P0981.pdf Link]</ref> for example synthesis of [[diazomethane]] from Diazald: |
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:[[Image:Preparation of diazomethane from Diazald and MNNG.svg|500px|Preparation of diazomethane from Diazald and MNNG]] |
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* [[Organic oxidation|oxidation]] of [[hydrazone]]s, for example with [[silver oxide]] or [[mercury oxide]] for example the synthesis of ''2-diazopropane'' from ''acetone hydrazone'' <ref>Organic Syntheses, Coll. Vol. 6, p.392 (1988); Vol. 50, p.27 (1970). [http://www.orgsynth.org/orgsyn/pdfs/CV6P0392.pdf Link]</ref> . |
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* Fragmentation of 1,3-disubstituted alkyl aryl [[triazene]]s |
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* One method is described for the synthesis of diazo compounds from [[azide]]s using [[phosphines]] <ref>''A Phosphine-Mediated Conversion of Azides into Diazo Compounds'' Eddie L. Myers and Ronald T. Raines [[Angew. Chem. Int. Ed.]] '''2009''', 48, 2359 –2363 {{DOI:10.1002/anie.200804689}}</ref>: |
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:[[Image:AzidetoDiazo Myers 2009.svg|Azide to diazo conversion]] |
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==Diazo reactions== |
==Diazo reactions== |
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* Diazo compounds react as 1,3-dipoles in [[diazoalkane 1,3-dipolar cycloaddition]]s. |
* Diazo compounds react as 1,3-dipoles in [[diazoalkane 1,3-dipolar cycloaddition]]s. |
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* Diazo compounds are used as precursors to [[carbene]]s, which are generated by thermolysis or photolysis, for example in the [[Wolff rearrangement]]. They are also used in [[transition metal]]-[[catalyst|catalyzed]] [[cyclopropane|cyclopropanation]] reactions for example in a synthesis of [[tranylcypromine]] <ref>''Catalytic Cyclopropanation of Alkenes Using Diazo Compounds Generated in Situ. A Novel Route to 2-Arylcyclopropylamines'' Varinder K. Aggarwal, Javier de Vicente, and Roger V. Bonnert Org. Lett.; '''2001'''; 3(17) pp 2785 - 2788; (Letter) [http://dx.doi.org/10.1021/ol0164177 Abstract]</ref> <ref>Notes: [[benzaldehyde]] reacts with [[p-toluenesulfonyl hydrazide]] to the [[hydrazone]].Its sodium salt reacts with [[N-Vinylphthalimide]] and [[rhodium acetate]], a [[phase transfer catalyst]] and [[phenylthiocarbamide|PTC]] to the cyclopropane. The phthalimide group is removed by [[hydrazine]]. The product is the [[cis isomer]] but by switching to [[ClFeTPP]] the amount of trans isomer increases to 33%</ref> in ''scheme 1'' {{Ref|scheme1}} in which the sodium salt of benzaldehyde [[tosyl hydrazone]] is converted to a [[rhodium]] [[metal carbene]] through the diazo intermediate. |
* Diazo compounds are used as precursors to [[carbene]]s, which are generated by thermolysis or photolysis, for example in the [[Wolff rearrangement]]. They are also used in [[transition metal]]-[[catalyst|catalyzed]] [[cyclopropane|cyclopropanation]] reactions for example in a synthesis of [[tranylcypromine]] <ref>''Catalytic Cyclopropanation of Alkenes Using Diazo Compounds Generated in Situ. A Novel Route to 2-Arylcyclopropylamines'' Varinder K. Aggarwal, Javier de Vicente, and Roger V. Bonnert Org. Lett.; '''2001'''; 3(17) pp 2785 - 2788; (Letter) [http://dx.doi.org/10.1021/ol0164177 Abstract]</ref> <ref>Notes: [[benzaldehyde]] reacts with [[p-toluenesulfonyl hydrazide]] to the [[hydrazone]].Its sodium salt reacts with [[N-Vinylphthalimide]] and [[rhodium acetate]], a [[phase transfer catalyst]] and [[phenylthiocarbamide|PTC]] to the cyclopropane. The phthalimide group is removed by [[hydrazine]]. The product is the [[cis isomer]] but by switching to [[ClFeTPP]] the amount of trans isomer increases to 33%</ref> in ''scheme 1'' {{Ref|scheme1}} in which the sodium salt of benzaldehyde [[tosyl hydrazone]] is converted to a [[rhodium]] [[metal carbene]] through the diazo intermediate. |
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:[[Image:Diazo cyclopropanation.png|600px|Scheme 1. Diazo cyclopropanation]] |
:[[Image:Diazo cyclopropanation.png|600px|Scheme 1. Diazo cyclopropanation]] |
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* Diazo compounds are intermediates in the [[Bamford-Stevens reaction]] of tosylhydrazones to alkenes |
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:[[Image:Bamford-Stevens reaction mechanism.svg|573px|Bamford-Stevens reaction]] |
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==Diazo biomolecules== |
==Diazo biomolecules== |
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[[Category:Functional groups]] |
[[Category:Functional groups]] |
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[[Category:Diazo compounds]] |
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[[es:Diazocompuesto]] |
[[es:Diazocompuesto]] |
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Revision as of 20:25, 27 March 2009
Diazo refers to a type of organic compound that has two linked nitrogen (azo) compounds. The general formula is R2C=N2. The simplest example of a diazo compound is diazomethane. The electronic structure of diazo compounds involves a positive charge on the central nitrogen and negative charge distributed between the terminal nitrogen and the carbon. Some of the most stable diazo compounds are α-diazoketones and α-diazoesters since the negative charge is delocalized into the carbonyl. In contrast, most alkyldiazo compounds are explosive. A commercially relevant diazocompound is Ethyl diazoacetate N2CHCOOEt. A group of isomeric compounds with similar properties are the diazirines, where the carbon and two nitrogens are linked as a ring.
A total of 4 resonance structures can be drawn [1]:
Diazo compounds should not be confused with azo compounds of the type R-N=N-R or with diazonium compounds of the type R-N2+.
Diazo synthesis
Several laboratory methods exist for the preparation of diazo compounds [2]:
- Reaction of an acyl halide with diazomethane [3], for example the first step in the Arndt-Eistert synthesis
- In diazo transfer certain carbon acids can be reacted with tosyl azide
- This reaction is also called the Regitz diazo transfer [4]. Examples are the synthesis of tert-butyl diazoaceate [5] and di-tert-butyl diazomalonate [6]
- Elimination reaction of N-alkyl-N-nitroso compounds [7] for example synthesis of diazomethane from Diazald:
- oxidation of hydrazones, for example with silver oxide or mercury oxide for example the synthesis of 2-diazopropane from acetone hydrazone [8] .
- Fragmentation of 1,3-disubstituted alkyl aryl triazenes
- One method is described for the synthesis of diazo compounds from azides using phosphines [9]:
Diazo reactions
- Diazo compounds react as 1,3-dipoles in diazoalkane 1,3-dipolar cycloadditions.
- Diazo compounds are used as precursors to carbenes, which are generated by thermolysis or photolysis, for example in the Wolff rearrangement. They are also used in transition metal-catalyzed cyclopropanation reactions for example in a synthesis of tranylcypromine [10] [11] in scheme 1 [1] in which the sodium salt of benzaldehyde tosyl hydrazone is converted to a rhodium metal carbene through the diazo intermediate.
- Diazo compounds are intermediates in the Bamford-Stevens reaction of tosylhydrazones to alkenes
Diazo biomolecules
An unusual biomolecule sporting a diazo group was synthesized in 2006 with in its final stage the reaction of a carbonyl group with the hydrazine 1,2-bis(tert-butyldimethylsilyl)hydrazine to the hydrazone followed by reaction with the periodinane difluoroiodobenzene to the diazo compound [12] [13]
See also
References
- ^ F.A. Carey R.J. Sundberg Advanced Organic Chemistry, 2nd Edition
- ^ March, Jerry (1985), Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, 3rd edition, New York: Wiley, ISBN 9780471854722, OCLC 642506595
- ^ Example Organic Syntheses, Coll. Vol. 3, p.119 (1955); Vol. 26, p.13 (1946).Link
- ^ M. Regitz, Angew. Chem., 79, 786 (1967); Angew. Chem. Intern. Ed. Engl., 6, 733 (1967).
- ^ Organic Syntheses, Coll. Vol. 5, p.179 (1973); Vol. 48, p.36 (1968). Link
- ^ Organic Syntheses, Coll. Vol. 6, p.414 (1988); Vol. 59, p.66 (1979). Link
- ^ Example: Organic Syntheses, Coll. Vol. 6, p.981 (1988); Vol. 57, p.95 (1977). Link
- ^ Organic Syntheses, Coll. Vol. 6, p.392 (1988); Vol. 50, p.27 (1970). Link
- ^ A Phosphine-Mediated Conversion of Azides into Diazo Compounds Eddie L. Myers and Ronald T. Raines Angew. Chem. Int. Ed. 2009, 48, 2359 –2363 {{DOI:10.1002/anie.200804689}}
- ^ Catalytic Cyclopropanation of Alkenes Using Diazo Compounds Generated in Situ. A Novel Route to 2-Arylcyclopropylamines Varinder K. Aggarwal, Javier de Vicente, and Roger V. Bonnert Org. Lett.; 2001; 3(17) pp 2785 - 2788; (Letter) Abstract
- ^ Notes: benzaldehyde reacts with p-toluenesulfonyl hydrazide to the hydrazone.Its sodium salt reacts with N-Vinylphthalimide and rhodium acetate, a phase transfer catalyst and PTC to the cyclopropane. The phthalimide group is removed by hydrazine. The product is the cis isomer but by switching to ClFeTPP the amount of trans isomer increases to 33%
- ^ Total Synthesis of the Diazobenzofluorene Antibiotic (-)-Kinamycin C1 Xiaoguang Lei and John A. Porco, Jr. J. Am. Chem. Soc.; 2006; ASAP Web Release Date: 26-Oct-2006; (Communication) doi:10.1021/ja066621v
- ^ Elusive Natural Product Is Synthesized Stu Borman Chemical & Engineering News October 31, 2006 Link.