| Nitro compounds are widely used in dyes,pharmaceuticals,pesticides,chemical fiber,rubber and explosives industries as an important class of chemical raw mater:ials.Thanks to the versatile conversions of nitro group into other functional groups,nitro compounds were regarded as "ideal intermediates in organic synthesis" and played a very important role.The nitrification of compounds mainly includes aliphatic and aromatic nitration.In general,the nitrating agent-participated electrophilic aromatic substitution has long been the predominant synthetic approach for the preparation of nitroarenes.Light alkanes and cycloalkanes are difficult to be nitrated by using mixed acid nitration due to their low reactivity toward nitrating agents,thus gas-phase nitration was usually used to prepare the corresponding nitroalkanes.However,the traditional methods always suffer from poor regio-and chemoselectivity,unsatisfied functional group and/or substrate compatibility,and environmental pollution.In recent years,transition metal-catalyzed carbon-hydrogen bond activation reactions have become a hot topic in the organic chemistry due to their great advantages,such as excellent regioselectivity,minimized reaction steps,low costs,and high atom-economy.On the basis of previous studies,we explored novel nitration reaction of carbon-hydrogen bonds by the transition metal with high selectivity.This dissertation includes two chapters as follows:1.We report a novel nitration of quinoxaline benzylic C-H bond mediated by AgN02 with high selectivity.This method for the first time realized the synthesis of quinoxaline containing nitroalkanes involving silver-mediated direct sp3 C-H bond nitration with advantages of high regioselectivity,simple operation,easy availability of the starting materials and high yield.2.Then,a palladium-catalyzed azobenzene ligand-directed ortho C-H bond nitration was developed.Using palladium acetate as the catalyst and azobenzene as the directing group,we achieved a highly regioselective nitration of C-H and sequentially provided a novel access to o-phenylenediamines via the reduction of the resulting nitrated products. |
