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Synthesis of α-Diazo Ketones
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Reaction of trimethylsilyldiazomethane with a mixed anhydride derived from a
carboxylic acid and ethyl chloroformate yields the corresponding
diazoketone in high yield. Subsequent Wolff rearrangement of the diazoketone
leads to the homologated ester. Reactions of trimethylsilyldiazomethane with
convenient active esters are described.
J. Cesar, M. Sollner Dolenc, Tetrahedron Lett.,
2001, 42, 7099-7102.
A 'sulfonyl-azide-free' ('SAFE') protocol for diazo transfer to CH-acidic
1,3-dicarbonyl compounds has been extended to less reactive monocarbonyl
substrates. In situ formylation, followed by the addition of an optimized amount
of a mixture of sodium azide, potassium carbonate, and m-carboxybenzenesulfonyl
chloride in water (SAFE cocktail) led to the formation of the desired diazo
compounds.
D. Dar'in, G. Kantin, M. Krasavin, Synthesis, 2019, 51,
4284-4292.
The reaction of 1,3-diketones, TsN3, and MeNH2 in EtOH
enables a highly efficient synthesis of α-diazoketone via a tandem reaction
including a novel primary amine-catalyzed Regitz diazo transfer of 1,3-diketones
and a novel primary amine-mediated C-C bond cleavage of 2-diazo-1,3-diketones.
J. Zhang, W. Chen, D. Huang, X. Zeng, X. Wang, Y. Hu, J. Org. Chem.,
2017, 82, 9171-9174.
α-Aryl-α-diazo ketones derived from direct diazo transfer with α-aryl ketones cyclize efficiently
in the presence of Rh catalysts to give the
corresponding α-aryl cyclopentanones.
D. F. Taber, W. Tian, J. Org. Chem., 2007,
72, 3207-3210.
Various diazoacetates were synthesized from the corresponding bromoacetates by
treatment with N,N'-ditosylhydrazine in moderate to high yields. Ease of
operation with the stable crystalline reagent as well as a short reaction time
offer a useful alternative to the conventional methods.
T. Toma, J. Shimokawa, T. Fukuyama, Org. Lett., 2007,
9, 3195-3197.
2-Azido-4,6-dimethoxy-1,3,5-triazine (ADT) as an intrinsically safe, highly
efficient, and shelf-stable diazo-transfer reagent. ADT is very stable upon >1
year storage under air at room temperature. Diazo-transfer reactions based on
ADT give diazo compounds in excellent yields within several minutes at room
temperature.
S. Xie, Z. Yan, Y. Li, Q. Song, M. Ma, J. Org. Chem., 2018, 83,
10916-10921.
Sulfonyl azides are potentially hazardous due to their propensity for explosive
decomposition under various reaction conditions. Polymer-supported
benzenesulfonyl azide provides a diazo transfer reagent with improved process
safety characteristics and thus offers an excellent reactant for laboratory use.
G. M. Green, N. P. Peet, W. A. Metz, J. Org. Chem., 2001,
66, 2509-2511.
2-Azido-1,3-dimethylimidazolinium chloride (ADMC) can be prepared by N-nitrosation
of N-aminoguanidine or by the reaction of
2-chloro-1,3-dimethylimidazolinium chloride and sodium azide. The corresponding
crystalline phosphate salt (ADMP) is a stable and safe reagent. Both ADMC and
ADMP reacted with 1,3-dicarbonyl compounds under mild conditions to give
2-diazo-1,3-dicarbonyl compounds in high yields.
M. Kitamura, N. Tashiro, S. Miyagawa, T. Okauchi, Synthesis, 2011,
1037-1044.
Diazo transfer from 2-azido-1,3-dimethylimidazolinium chloride to 1,3-dicarbonyl
compounds proceeds under mild conditions to give 2-diazo-1,3-dicarbonyl
compounds in high yields, which are easily isolated because the by-products are
highly soluble in water.
M. Kitamura, N. Tashiro, T. Okauchi, Synlett, 2009,
2931-2934.
Diazo-transfer reactions with tosyl azide followed by efficient chromatographic
purifications on silica gel and/or alumina enable a practical protocol for the
large-scale preparation of 2-diazo-1,3-dicarbonyl compounds.
M. Presset, D. Mailhol, Y. Coquerel, J. Rodriguez, Synthesis, 2011,
2549-2552.
The reaction of triflyl azide with α-nitrocarbonyl compounds in the presence of
pyridine enables a highly efficient preparation of α-nitro-α-diazocarbonyl
derivatives.
A. B. Charette, R. P. Wurz, T. Ollevier, J. Org. Chem., 2000,
65, 9252-9254.