ABSTRACT
The effect of water on the NH3-assisted selective catalytic reduction of NOx (NH3-SCR) has been largely neglected, despite the inevitable presence of water vapor in real emissions produced by fuel combustion. In this work, we investigated the role of water in the behavior of active Cu2+ ions in Cu-SSZ-13 in the NH3-SCR reaction. The addition of water to the reactant feed leads to significantly increased NOx reduction over the catalyst. By combining in situ DRIFTS and XANES analyses during the NH3-SCR reaction, we found that the redox cycle of Cu ions is promoted by the presence of water.
ABSTRACT
Due to its superior ability in controlling pharmaceutical activity, the installation of difluoromethyl (CF2H) functionality into organic molecules has been an area of intensive research. In this context, difluoromethylation of C-C π bonds mediated by a CF2H radical have been pursued as a central strategy to grant access to difluoromethylated hydrocarbons. However, early precedents necessitate the generation of oxidative chemical species that can limit the generality and utility of the reaction. We report here the successful implementation of radical hydrodifluoromethylation of unsaturated C-C bonds via an electroreductively triggered two-pronged approach. Preliminary mechanistic investigations suggest that the key distinction of the present strategy originates from the reconciliation of multiple redox processes under highly reducing electrochemical conditions. The reaction conditions can be chosen based on the electronic properties of the alkenes of interest, highlighting the hydrodifluoromethylation of both unactivated and activated alkenes. Notably, the reaction delivers geminal (bis)difluoromethylated products from alkynes in a single step by consecutive hydrodifluoromethylation, granting access to an underutilized 1,1,3,3-tetrafluoropropan-2-yl functional group. The late-stage hydrodifluoromethylation of densely functionalized pharmaceutical agents is also presented.
