Categories: C=N Bond Formation >
Synthesis of α-Diazo Esters and Amides
A water-soluble phosphinoester mediates an efficient conversion of azides into diazo compounds in phosphate buffer at neutral pH and room temperature. High yields are maintained in the presence of common nucleophilic or electrophilic functional groups, and reaction progress can be monitored by colorimetry.
H.-H. Chou, R. T. Raines, J. Am. Chem. Soc., 2013, 135, 14936-14939.
A safe and fast method for the production of β-hydroxy-α-diazoesters involves the formation of ethyl diazoacetate in situ and the addition to several aldehydes in a two-step continuous flow microreactor setup. In a three-step sequence, Rhodium acetate catalyzes a subsequent 1,2-hydride shift to give access to β-keto esters.
S. T. R. Müller, D. Smith, P. Hellier, T. Wirth, Synlett, 2014, 25, 871-875
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.
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.
Lewis acids catalyze the cyclization of methyl phenyldiazoacetates with an ortho-imino group, prepared from o-aminophenylacetic acid, to give 2,3-substituted indoles in quantitative yields.
L. Zhou, M. P. Doyle, J. Org. Chem., 2009, 74, 9222-9224.