title: Catalytic N-radical cascade reaction of hydrazones by oxidative deprotonation electron transfer and TEMPO mediation.
abstract: Compared with the popularity of various C-centred radicals, the N-centred radicals remain largely unexplored in catalytic radical cascade reactions because of a lack of convenient methods for their generation. Known methods for their generation typically require the use of N-functionalized precursors or various toxic, potentially explosive or unstable radical initiators. Recently, visible-light photocatalysis has emerged as an attractive tool for the catalytic formation of N-centred radicals, but the pre-incorporation of a photolabile groups at the nitrogen atom largely limited the reaction scope. Here, we present a visible-light photocatalytic oxidative deprotonation electron transfer/2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediation strategy for catalytic N-radical cascade reaction of unsaturated hydrazones. This mild protocol provides a broadly applicable synthesis of 1,6-dihydropyradazines with complete regioselectivity and good yields. The 1,6-dihydropyradazines can be easily transformed into diazinium salts that showed promising in vitro antifungal activities against fungal pathogens. DFT calculations are conducted to explain the mechanism.
authors.affiliation: CCNU-uOttawa Joint Research Centre, Key Laboratory of Pesticide and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, 152 Luoyu Road, Wuhan 430079, China.
authors.forename: Xiao-Qiang
authors.initials: XQ
authors.lastname: Hu
authors.affiliation: School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400030, China.
authors.forename: Xiaotian
authors.initials: X
authors.lastname: Qi
authors.affiliation: CCNU-uOttawa Joint Research Centre, Key Laboratory of Pesticide and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, 152 Luoyu Road, Wuhan 430079, China.
authors.forename: Jia-Rong
authors.initials: JR
authors.lastname: Chen
authors.affiliation: CCNU-uOttawa Joint Research Centre, Key Laboratory of Pesticide and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, 152 Luoyu Road, Wuhan 430079, China.
authors.forename: Quan-Qing
authors.initials: QQ
authors.lastname: Zhao
authors.affiliation: CCNU-uOttawa Joint Research Centre, Key Laboratory of Pesticide and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, 152 Luoyu Road, Wuhan 430079, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Wei
authors.affiliation: School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400030, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Lan
authors.affiliation: CCNU-uOttawa Joint Research Centre, Key Laboratory of Pesticide and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, 152 Luoyu Road, Wuhan 430079, China.
authors.forename: Wen-Jing
authors.initials: WJ
authors.lastname: Xiao