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Zusammenfassung:
The Co-catalyzed coupling of three-membered ring heterocycles with alkenes has provided a new synthetic route to challenging substrates such as cyclic homoallylic alkohols and amines starting form easily accessible materials. During the studies of this transformation, it has been discovered that the intermediate generated during the reaction (e.g. alkoxide formation after epoxide opening) is basic enough to deprotonate the metal hydride species generated at the end of the catalytic cycle, thus providing catalytic turnover without need of external reductants or stoichiometric amount of additional base. In a broader context, this discovery might inspire the design of novel atom-economical transformations involving the alkylation of different electrophiles (from a nucleophilic Co(I)-species) and generation of similar basic intermediates able to directly regenerate the active catalyst.
In conclusion, a conceptually novel strategy for the synthesis of a broad array of primary amines building blocks through the synthesis of rare unprotected aminochlorides has been reported. These versatile intermediates can be generated for the first time from alkenes through the use of an operationally simple Fe-catalyzed aminochlorination reaction that uses a hydroxylamine-derivative reagent and benign NaCl as a stoichiometric chlorinating agent. This protocol tolerates a large scope of aliphatic and conjugated alkenes, including densely functionalized substrates, and gives perfect regioselectivy for the anti-Markovnikov installation of the amino group. The unique reactivity of this poorly studied class of amphoteric molecules enables a facile access to mono- and difunctionalized primary amine derivatives, such as linear or branched primary amines, aziridines, cyano amines, azido amines and allyl amines. This operationally simple Fe-catalyzed protocol thus provides a unified two-step strategy for the synthesis of a wide range of primary amine containing building blocks, formally addressing multiple longstanding challenges in catalysis, such as the catalytic synthesis of linear primary amines from alpha alkenes.
