Photocatalytic Multicomponent 1,n-Carboimination with Alkyl Iodides and O-Benzoyl Oxime through EnT and XAT Processes

Abstract

In this study, we developed a strategy using commercially available alkyl iodides and O-benzoyl oxime to efficiently introduce alkyl and iminyl groups via energy transfer and halogen-atom transfer processes. We performed threecomponent 1,2-carboimination of olefins and four-component 1,4carboimination across olefins and alkynes, resulting in the synthesis of over 60 nitrogen-containing molecules. Moreover, this transformation enables the synthesis of molecules with sensitive groups that were previously difficult to achieve.

Three-Component Photochemical 1,2,5-Trifunctionalizations of Alkenes toward Densely Functionalized Lynchpins

“…Lastly, we questioned the underlying mechanism for the terminal installation of the imine group. For other reactions involving energy transfer-cleavable imine-based bifunctional reagents, this step was proposed to proceed either via radical recombination with a free iminyl radical or via reaction with the bifunctional reagent with subsequent release of a transient radical in a radical chain manner. , Consequently, we determined the reaction quantum yield for the formation of 4a and obtained a value of Φ = 1.91 (Figure F). This result suggests imine installation via a radical chain mechanism, albeit not ruling out a radical recombination mechanism operating in parallel.…”

“…Additionally, we aimed at utilizing the necessary radical relocation to install a synthetically versatile functional group in 2-position. For this purpose, we envisioned a mechanism using energy transfer-cleavable imine-based bifunctional reagents, which were mainly pioneered by our group (Figure B). ,,, Homolytic cleavage of the bifunctional reagent upon energy transfer would deliver a persistent, ambiphilic iminyl radical and a transient, electrophilic chalcogenyl radical. The formed chalcogenyl radical could then add to an allylboronic ester in a polarity-matched manner, followed by fast 1,2-boron migration to form a more stabilized tertiary radical.…”

“…Such 1,2-boron shifts were previously utilized by Studer and others to achieve 1,3-difunctionalizations, as well as 1,3- and 1,5-hydrofunctionalizations of alkenes . Subsequent, polarity-matched addition of the generated nucleophilic, carbon-centered radical to a Michael acceptor, and terminal radical recombination with an iminyl radical or reaction with the bifunctional reagent in a radical chain manner would deliver the desired 1,2,5-trifunctionalized product. ,,, Therefore, this approach would be suitable to provide diverse, protected 1,5-amino alcohols and 1,5-amino sulfones which are important motifs in biologically active compounds and valuable synthetic precursors …”