A general and regiospecific transformation of substituted phenols into the related o-nitrophenols has been achieved via a three-step process involving the palladium-catalyzed chelation-assisted ortho-C-H bond nitration as the key step. In the process, 2-pyridinyloxy groups act as removable directing groups for the palladium-catalyzed ortho-nitration of substituted 2-phenoxypridines, and they can be readily removed in the subsequent conversion of the resulting 2-(2-nitrophenoxy)pyridines into 2-nitrophenols.
Palladium-catalyzed nitration of 8-methylquinolines with t-BuONO to give 8-(nitromethyl)quinolines in moderate to excellent yields has been developed involving an sp(3) C-H bond activation. The resulting (nitromethyl)quinolines could be selectively reduced to (1,2,3,4-tetrahydroquinolin-8-yl)methanamines by NaBH4 in the presence of a catalytic amount of NiCl2·6H2O.
A novel and facile method for the mild construction of fluorinated fluorenones from nonaromatic precursors (1,6-enynes) mediated by a Cu(0)/Selectfluor system has been successfully achieved. Preliminary mechanistic investigations indicate that the reaction may proceed via an unprecedented annulation/C-C single bond cleavage/fluorination sequence.
Selectfluor-mediated simultaneous cleavage of C-O and C-C bonds in α,β-epoxy ketones has been successfully achieved under transition-metal-free conditions. The reaction gives 1,2-diketone compounds in moderate to good yields involving a ring-opening/benzoyl rearrangement/C-C bond cleavage sequence under oxidative conditions.
A route to β-substituted cyclohex-2-enones, 4-arylcoumarins, and biaryls has been developed. This approach involves a one-pot Cu 0 /Selectfluor-catalyzed dehydration-oxidation of tertiary cycloalcohols. Thus, by using 2 equiv. of Selectfluor at 25°C, the dehydration-oxidation of tertiary cyclohexanols
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