Visible light-induced intramolecular cyclization reactions of diamines: a new strategy to construct tetrahydroimidazoles

Abstract

A new and efficient synthesis of highly substituted tetrahydroimidazole derivatives by means of visible light-induced intramolecular cyclization reactions has been described. This photoredox catalytic reaction exhibited high diastereoselectivity and afforded the desired products in good yields.

Visible Light Photoredox Catalysis with Transition Metal Complexes: Applications in Organic Synthesis

“…96 Using Ru(bpy) 3 2+ as the photocatalyst and oxygen as the stoichiometric oxidant, diamine 136 is converted to iminium ion 137 , which upon cyclization yields the product tetrahydroimidazole 138 (Scheme 31). The cis diastereomer may be obtained with high selectivity if the reaction is performed for an extended period of time, presumably due to postreaction epimerization at the aminal carbon.…”

The chemistry of amine radical cations produced by visible light photoredox catalysis

“…The Xiao group developed a highly diastereroselective route to substituted tetrahydroimidazoles 72 based on intramolecular interception of the iminium ions by a tethered sulfonamide ( 71 , Scheme 18) [86]. Ru(bpy) 3 Cl 2 was employed as the photocatalyst with oxygen as the stoichiometric oxidant.…”

Highly Efficient Aerobic Oxidative Hydroxylation of Arylboronic Acids: Photoredox Catalysis Using Visible Light

“…We recently developed a visiblelight-induced oxidation/[3+2] cycloaddition/oxidative aromatization sequence for dihydroisoquinoline esters and electrondeficient alkenes or alkynes to construct pyrrolo[2,1-a] isoquinolines. [15,16] In this sequence, a superoxide radical anion, which was generated from molecular oxygen, plays a key role throughout the process. Based on the investigation of the mechanism, we envisioned that this kind of highly active species might have Lewis basicity and therefore react with the appropriate acidic components.…”