K2S2O8-mediated nitration of alkenes with NaNO2 and 2,2,6,6-tetramethylpiperidine-1-oxyl: stereoselective synthesis of (E)-nitroalkenes

A transition-metal-free nitration of alkenes with NaNO2 in the presence of K2S2O8 and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) is developed. The transformation exhibits a broad substrate scope and good functional group tolerance, thus providing a new and expedient protocol for stereoselective synthesis of (E)-nitroalkenes with moderate to good yields. Moreover, the nitration processes of (E)- and (Z)-stilbene are also studied: even though the proportion of substrates is different, the E/Z ratio of the products is basically the same. Based upon experimental observations, a possible reaction mechanism is proposed. (C) 2015 Elsevier Ltd. All rights reserved.