Homohalocyclization: Electrophilic Bromine-Induced Cyclizations of Cyclopropanes

Abstract

An efficient method for the halocyclization of cyclopropanes has been developed. The cyclopropanes undergo a 1,3-addition reaction to form homohalocyclization products compared to conventional alkene halocyclizations. The reaction can be induced by various electrophilic halogenating agents including 1,3-dibromo-5,5-dimethylhydantoin and N-iodosuccinimide. In cyclopropane derivatives with a preexisting stereocenter, excellent induced diastereoselectivities can be observed.

Ring-opening hydroarylation of monosubstituted cyclopropanes enabled by hexafluoroisopropanol

“…Existing ring-opening reactions include oxidative addition into C–C bonds with transition metals, 6 – 8 oxidative 1,3-difunctionalization, 9 frustrated Lewis pairs, 10 , 11 or addition of strong nucleophiles 12 – 14 and mineral acids. 15 One-pot iodination/alkylation procedures are also known. 16 Our laboratory has begun to exploit the catalytically active aggregates formed between Brønsted acids and solvents such as hexafluoroisopropanol (HFIP) to enable challenging transformations.…”

Electrophilic Bromolactonization of Cyclopropyl Carboxylic Acids Using Lewis Basic Sulfide Catalyst

“…[4] Very recently Hennecke reported the cyclization of 1a using 1,3-dibromo-5,5-dimethylhydantoin (DBH) in the absence of catalyst. [5] As part of the research interests in Lewis base-catalyzed halocyclization reactions in our team, we reported aL ewis basic sulfide-catalyzed electrophilic bromocyclization of cyclopropylmethyl amide very recently. [6] In ap arallel research program, we are also studyingt he bromocyclizationo fc yclopropylcarboxylic acid 1.H owever, after examining the reactioncarefully it was found that such areaction could not proceed in the absence of light (vide infra, Table 1).…”

Electrophilic Bromolactonization of Cyclopropyl Diesters Using Lewis Basic Chalcogenide Catalysts

“…Recently, Hennecke et al. reported a range of catalyst‐free halocyclization of cyclopropanes with tosylamides, hydroxyl, and carboxyl substituents, yielding the corresponding pyrrolidines, tetrahydrofurans and lactones, respectively . An emerging research direction involves the oxidative ring‐opening/functionalization of unactivated cyclopropanes using hypervalent iodine species…”