Cover Feature: Lewis Base Catalysis Enables the Activation of Alcohols by means of Chloroformates as Phosgene Substitutes (ChemCatChem 22/2020). Issue 22 (15th October 2020) - Zoller, Ben
Abstract : The Cover Feature shows the Lewis base‐catalyzed activation of alcohols for nucleophilic substitutions (S N ) using phenyl chloroformate (PCF) as inherently safe phosgene substitute. In their Full Paper, B. Zoller et al. explain that S N ‐reactions are typically facilitated by stoichiometric reagents, which effect an enhanced thermodynamic driving force and favourable kinetics. In fact, phosgene (COCl2 ) is the least expensive reagent for initiation of S N ‐type transformations. However, it is also a highly toxic gas, which was used as warfare agent. We discovered that phosgene can be replaced by much less hazardous PCF in C−Cl and C−Br bond formations, if a suitable Lewis base catalyst is involved. In addition, the use of PCF also resulted in improved yields, as shown by a rigorous comparison. Importantly, the reaction by‐product phenol can be recycled in an industrial setting using cost‐efficient phosgene. More information can be found in the Full Paper by B. Zoller et al.