Photogenerated-radical cyclopropylation of in situ generated iminiums mediated by NaI/PPh3: direct access to α-cyclopropyl tertiary alkylamines

Abstract

Using cyclopropyl radicals to install cyclopropanes has been a fast-growing research field in recent years. Meanwhile, direct radical carbonyl alkylative amination has emerged as an ideal protocol for constructing α-branched tertiary amines. Based on the strategy of direct addition of cyclopropyl radicals to in situ generated iminium ions, we disclose a method for preparing diverse α-cyclopropyl tertiary alkylamines by photogenerated-radical cyclopropylation mediated by NaI/PPh₃ using abundant feedstocks (aldehydes and amines) and easily procured cyclopropyl active esters. Importantly, NaI/PPh₃ works as both the photoinitiator and sacrificial reductant in this reaction and hence gives an economical variant of carbonyl alkylative amination under mild reaction conditions. In addition, the electrochemical variant of this photogenerated-radical cyclopropylation was also investigated with the preliminary results.