82973-11-3Relevant academic research and scientific papers
Experimental and Theoretical Studies on the Mechanism of DDQ-Mediated Oxidative Cyclization of N-Aroylhydrazones
Baek, Jihye,Je, Eun-Kyung,Kim, Jina,Qi, Ai,Ahn, Kwang-Hyun,Kim, Yongho
, p. 9727 - 9736 (2020)
The controversial single-electron-transfer process, frequently proposed in many 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)-mediated reactions, was investigated experimentally and theoretically using the oxidative cyclization of aroylhydrazone with DDQ. DDQ-mediated oxadiazole formation involves several processes, including cyclization to form an oxadiazole ring and N-H bond cleavage, either by proton, hydride, or hydrogen atom transfer. The detailed mechanistic study using the M06-2X density functional theory, and the 6-31+G(d,p) basis set, suggests that the pathways involving radical ion pair (RIP) intermediates, which resulted from single-electron transfer (SET), were found to be energetically nearly identical to the pathway without the SET. The substituent-dependent reactivity of oxadiazole formation was consistent with the free energy profiles of both pathways, with or without the SET. This result indicates that in addition to the electron-transfer pathway, the nucleophilic addition/elimination pathway for DDQ should be considered as a possible mechanism of the oxidative transformation reaction using DDQ.
