Synthesis and characterization of phenyl-substituted C-phenyl-N-tert-butylnitrones and some of their radical adducts
摘要:
Synthesis of C-phenyl-N-tert-butylnitrone (PBN) and several of its analogues with substituents in the 2-, 3-, or 4-position on the phenyl ring is described. While a one-pot reduction/condensation method proved suitable for most compounds, it was necessary to prepare some examples by direct condensation or through oxidation of the appropriate imine. The H-1 NMR data for the 3-X- and 4-X-PBN's can be correlated with the Hammett equation. For the 3-X series DELTA-delta for the alpha-proton correlates best with sigma(+) and has a correlation coefficient of 0.90. For the 4-X series a dual substituent parameter equation using sigma(R)0 gives the best correlation with r = 0.99. The hyperfine splitting constants (hfsc's) of the HO. and HOO. adducts of several substituted PBN's are also included and their correlation with the Hammett equation is discussed.
Palladium-catalyzed C–H alkenylation of C-aryl N-t-butyl nitrones with ethyl acrylate produced ortho-alkenylated benzamide derivatives via isomerization of the nitrone moiety. The use of 1,1,1,3,3,3-hexafluoro-2-propanol/acetic acid as a solvent resulted in effective C–H alkenylation, while competitive 1,3-dipolar cycloaddition was completely suppressed.
Iridium(III)-Catalyzed C–H Amidation of Nitrones with Dioxazolones
作者:Xia Mi、Weisheng Feng、Chao Pi、Xiuling Cui
DOI:10.1021/acs.joc.9b00300
日期:2019.5.3
efficiently achieved through Ir(III)-catalyzed direct C–H amidation of nitrones with good to excellent yields and tolerance of broad functional groups. This reaction smoothly proceeded at roomtemperature in the absence of acid or base in a short reaction time. Carbon dioxide was generated as the sole byproduct, thus providing an environmentally benign amidation process. The title products could be efficiently