Categories: C=N Bond Formation >
Synthesis of α-Diazo Esters
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-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.