Alkene versus Aryl Chlorination in Asymmetric Hypervalent Iodine Catalysis: A Case Study

Abstract

Hypervalent λ3-iodanes have become a prominent tool for halofunctionalizations of alkenes. Despite many examples of asymmetric fluorinations reported lately, the corresponding enantioselective chlorination reactions using iodoresorcinol-based catalysts are significantly less developed, with only one example known to date. Here, we show how competing aromatic chlorination of the iodoarene catalyst is a significant obstacle in these transformations, hinting towards a conceptual issue with this well-established catalyst class for enantioselective chlorinations. Consequently, the reaction conditions and the catalyst design must be adapted to facilitate an effective chirality transfer. Hence, attention should be paid when selecting the oxidizing agent, the stoichiometry, and careful reaction analysis must be conducted to identify the factual catalytically active species.