Difference between revisions of "Hydrazone"

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==Preparation==
 
==Preparation==
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Substituted hydrazines will react directly with carbonyl compounds to form the corresponding hydrazone.<ref>{{OrgSynth | first1 = G. | last1 = Stork | first2 = J. | last2 = Benaim | title = Monoalkylation of α,β-Unsaturated Ketones ''via'' Metalloenamines: 1-butyl-10-methyl-Δ<sup>1(9)</sup>-2-octalone | collvol = 6 | collvolpages = 242 | volume = 57 | pages = 69 | year = 1977 | prep = cv6p0242}}.</ref> The reaction follows the normal [[addition–elimination mechanism]] for reactions at carbonyl carbon, and is [[Acid catalysis|acid-catalyzed]].
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Substituted hydrazines will react directly with carbonyl compounds to form the corresponding hydrazone.<ref>{{OrgSynth | first1 = G. | last1 = Stork | first2 = J. | last2 = Benaim | title = Monoalkylation of α,β-unsaturated ketones ''via'' metalloenamines: 1-butyl-10-methyl-Δ<sup>1(9)</sup>-2-octalone | collvol = 6 | collvolpages = 242 | volume = 57 | pages = 69 | year = 1977 | prep = cv6p0242}}.</ref> The reaction follows the normal [[addition–elimination mechanism]] for reactions at carbonyl carbon, and is [[Acid catalysis|acid-catalyzed]].
  
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The direct reaction cannot be used with [[hydrazine]] itself, as the hydrazone that is initially formed will react with a second equivalent of the carbonyl compound to form an [[azine]]. However the azine can be isolated, and then reacted with excess hydrazine to reform the hydrazone.<ref name="acetone">{{OrgSynth | first1 = A. C. | last1 = Day | first2 = M. C. | last2 = Whiting | title = Acetone hydrazone | collvol = 6 | collvolpages = 10 | volume = 50 | pages =3 | year = 1970 | prep = cv6p0010}}.</ref><ref name="Ber">{{citation | first1 = H. | last1 = Staudinger | first2 = Alice | last2 = Gaule | title = Vergleich der Stickstoff-Abspaltung bei verschiedenen aliphatischen Diazoverbindungen | journal = Ber. Dtsch. Chem. Ges. | year = 1916 | volume = 49 | issue = 2 | pages = 1897–1918 | doi = 10.1002/cber.19160490245}}.</ref>
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The direct reaction cannot be used with [[hydrazine]] itself, as the hydrazone that is initially formed will react with a second equivalent of the carbonyl compound to form an [[azine]]. However the azine can be isolated, and then reacted with excess hydrazine to reform the hydrazone.<ref name="acetone">{{OrgSynth | first1 = A. C. | last1 = Day | first2 = M. C. | last2 = Whiting | title = Acetone hydrazone | collvol = 6 | collvolpages = 10 | volume = 50 | pages =3 | year = 1970 | prep = cv6p0010}}.</ref><ref name="Ber">{{citation | first1 = H. | last1 = Staudinger | first2 = Alice | last2 = Gaule | title = Vergleich der Stickstoff-Abspaltung bei verschiedenen aliphatischen Diazoverbindungen | journal = Ber. Dtsch. Chem. Ges. | year = 1916 | volume = 49 | issue = 2 | pages = 1897–1918 | doi = 10.1002/cber.19160490245}}.</ref> A similar method is to form the ''N'',''N''-dimethylhydrazone, and then to react it with hydrazine to form the unsubstituted hydrazone.<ref>{{OrgSynth | first1 = G. R. | last1 = Newkome | first2 = D. L. | last2 = Fishel | title = Preparation of hydrazones: acetophenone hydrazone | collvol = 6 | collvolpages = 12 | volume = 50 | pages = 102 | year = 1970 | prep = cv6p0012}}.</ref>
  
 
==Reactions and uses==
 
==Reactions and uses==

Revision as of 20:00, 19 September 2010

Hydrazones are a functional class of organic compounds formed by the condensation reaction of hydrazine (or, more usually, an N-substituted hydrazine) with an aldehyde or a ketone.[1][2]

Preparation

Substituted hydrazines will react directly with carbonyl compounds to form the corresponding hydrazone.[3] The reaction follows the normal addition–elimination mechanism for reactions at carbonyl carbon, and is acid-catalyzed.

The direct reaction cannot be used with hydrazine itself, as the hydrazone that is initially formed will react with a second equivalent of the carbonyl compound to form an azine. However the azine can be isolated, and then reacted with excess hydrazine to reform the hydrazone.[4][5] A similar method is to form the N,N-dimethylhydrazone, and then to react it with hydrazine to form the unsubstituted hydrazone.[6]

Reactions and uses

Hydrazones can be hydrolysed to the corresponding carbonyl compounds: the reaction is usually endothermic and is acid-catalyzed. An excess of acid is often used to remove the hydrazine as a hydrazonium salt.

The 1-aminopyrrolidine derivatives RAMP and SAMP[7] are chiral auxiliaries that function by forming hydrazones with carbonyl groups in the compound to be derivatized.[8][9]

Notes and references

Notes

References

  1. ↑ Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995). Pure Appl. Chem. 1995, 67 (8-9), 1307–75 at 1341. DOI: 10.1351/pac199567081307.
  2. ↑ hydrazones, <http://goldbook.iupac.org/H02884.html> (accessed 20 September 2010), Compendium of Chemical Terminology Internet edition; International Union of Pure and Applied Chemistry (IUPAC).
  3. ↑ Stork, G.; Benaim, J. Monoalkylation of α,β-unsaturated ketones via metalloenamines: 1-butyl-10-methyl-Δ1(9)-2-octalone. Org. Synth. 1977, 57, 69, <http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv6p0242>; Coll. Vol., 6, 242.
  4. ↑ Day, A. C.; Whiting, M. C. Acetone hydrazone. Org. Synth. 1970, 50, 3, <http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv6p0010>; Coll. Vol., 6, 10.
  5. ↑ Staudinger, H.; Gaule, Alice Vergleich der Stickstoff-Abspaltung bei verschiedenen aliphatischen Diazoverbindungen. Ber. Dtsch. Chem. Ges. 1916, 49 (2), 1897–1918. DOI: 10.1002/cber.19160490245.
  6. ↑ Newkome, G. R.; Fishel, D. L. Preparation of hydrazones: acetophenone hydrazone. Org. Synth. 1970, 50, 102, <http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv6p0012>; Coll. Vol., 6, 12.
  7. ↑ Enders, Dieter; Fey, Peter; Kipphardt, Helmut (S)-(−)-1-Amino-2-methoxymethylpyrrolidine (SAMP) and (R)-(+)-1-amino-2-methoxymethylpyrrolidine (RAMP), versatile chiral auxiliaries. Org. Synth. 1987, 65, 173, <http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv8p0026>; Coll. Vol., 8, 26.
  8. ↑ Enders, D. Enantioselective alkylation of aldehydes via metalated chiral hydrazones. Tetrahedron Lett. 1977, 18 (2), 191–94. DOI: 10.1016/S0040-4039(01)92585-7.
  9. ↑ Enders, Dieter; Kipphardt, Helmut; Fey, Peter Asymmetric syntheses using the SAMP-/RAMP-hydrazone method: (S)-(+)-4-methyl-3-heptanone. Org. Synth. 1987, 65, 183, <http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV8P0403>; Coll. Vol., 8, 403.
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