2-Azaadamantane N-Oxyl, AZADO
2-Azaadamantane N-Oxyl (AZADO) is a less hindered nitroxyl radical, that exhibits an enhanced reactivity compared with TEMPO.
The use of tert-butyl nitrite as the co-catalyst in a 2-azaadamantane-N-oxyl (AZADO)- and 9-azanoradamantane-N-oxyl (nor-AZADO)-catalyzed efficient aerobic oxidation of primary alcohols in MeCN instead of the previously reported AcOH provides the corresponding aldehydes selectively. The addition of saturated aqueous NaHCO3 after the completion of the reaction suppresses the overoxidation of the product during the workup.
M. Shibuya, K. Furukawa, Y. Yamamoto, Synlett, 2017, 28, 1554-1557.
A stable nitroxyl radical class of catalysts, 2-azaadamantane N-oxyl (AZADO) and 1-Me-AZADO, exhibit superior catalytic proficiency to TEMPO, converting various sterically hindered alcohols to the corresponding carbonyl compounds in excellent yields.
M. Shibuya, M. Tomizawa, I. Suzuki, Y. Iwabuchi, J. Am. Chem. Soc., 2006, 128, 8412-8413.
A smooth, organocatalytic one-pot oxidative cleavage of terminal 1,2-diols to one-carbon-unit-shorter carboxylic acids is catalyzed by 1-Me-AZADO in the presence of a catalytica amount of NaOCl and NaClO2 under mild conditions. A broad range of substrates including carbohydrates and N-protected amino diols were converted without epimerization.
M. Shibuya, R. Doi, T. Shibuta, S.-i. Uesugi, Y. Iwabuchi, Org. Lett., 2012, 14, 5006-5009.
A chemoselective oxidation of α-hydroxy acids to α-keto acids is catalyzed by 2-azaadamantane N-oxyl (AZADO), a nitroxyl radical catalyst. The use of molecular oxygen as a cooxidant enables the desired chemoselective oxidation to α-keto acids, that are labile and can easily release CO2 under oxidation conditions.
K. Furukawa, H. Inada, M. Shibuya, Y. Yamamoto, Org. Lett., 2016, 18, 4230-4233.