A novel synthesis of 1,2,4-oxadiazoles and isoxazoles

A novel synthesis of 1,2,4-oxadiazoles and isoxazoles is described by utilizing the reactions between amidoximes and alpha,beta-alkynic aldehydes and/or ketones. Conjugate addition products, obtained from amidoximes and alpha,beta-alkynic aldehydes and/or ketones, afford 1,2,4-oxadiazoles and isoxazoles when treated with bases and acids, respectively. 1,2,4-Oxadiazoles can also be synthesized directly from amidoximes and alpha,beta-alkynic aldehydes in a one-pot manner under basic conditions. The reactions are general for a variety of starting compounds and tolerate the presence of aryl, heteroaryl and alkyl groups. (C) 2013 Elsevier Ltd. All rights reserved.