Hydrazone
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]
Contents
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 α-hydrogen of hydrazones is ten orders of magnitude more acidic than that of the corresponding ketone, and can easily be removed with lithium diisopropylamide (LDA) to form an azaenolate.[7][8]
The 1-aminopyrrolidine derivatives RAMP and SAMP[9] are chiral auxiliaries that function by forming hydrazones with carbonyl groups in the compound to be derivatized.[10][11]
Notes and references
Notes
References
- ↑ 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.
- ↑ 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).
- ↑ 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.
- ↑ 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.
- ↑ 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.
- ↑ 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.
- ↑ Corey, E. J.; Enders, Dieter Applications of N,N-dimethylhydrazones to synthesis. Use in efficient, positionally and stereochemically selective C–C bond formation; oxidative hydrolysis to carbonyl compounds. Tetrahedron Lett. 1976, 17 (1), 3–6. DOI: 10.1016/S0040-4039(00)71307-4.
- ↑ Corey, Elias J.; Enders, Dieter Herstellung und synthetische Verwendung von metallierten Dimethylhydrazonen Regio- und stereoselektive Alkylierung von Carbonylverbindungen. Chem. Ber. 1978, 111 (4), 1337–61. DOI: 10.1002/cber.19781110413.
- ↑ 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.
- ↑ 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.
- ↑ 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.
Further reading
- Lazny, Ryszard; Nodzewska, Aneta N,N-Dialkylhydrazones in Organic Synthesis: From Simple N,N-Dimethylhydrazones to Supported Chiral Auxiliaries. Chem. Rev. 2010, 110 (3), 1386–1434. DOI: 10.1021/cr900067y.
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