Regiospecific Intermolecular Aminohydroxylation of Olefins by Photoredox Catalysis

Abstract

A simple and regiospecific aminohydroxylation of olefins by photoredox catalysis has been developed. N-protected 1-aminopyridinium salts are the key compounds and serve as amidyl radical precursors by the action of Ir photocatalysts, fac-[Ir(ppy)3] and [Ir(ppy)2 (dtbbpy)](PF6) (ppy=2-pyridylphenyl, dtbbpy=4,4'-di-tert-butyl-2,2'-bipyridine). The present photocatalytic system allows for synthesis of vicinal aminoalcohol derivatives from olefins with various functional groups under mild reaction conditions with easy handling.

Organophotocatalytic Generation of N‐ and O‐Centred Radicals Enables Aerobic Oxyamination and Dioxygenation of Alkenes

“…In this context, the photocatalytic N‐ or O‐centred radical‐mediated oxidative oxyamination and dioxygenation of alkenes remain largely unexplored because of the limited methods for their efficient generation . The seminal studies by the groups of MacMillan, Sanford, and others– have demonstrated that the incorporation of a photolabile moiety into the amine substrates enable photocatalytic formation of N‐centred radicals and subsequent C−N bond formation. We, and Knowles have independently reported that visible‐light photocatalysis enabled the direct conversion of otherwise unreactive N−H bonds into N‐centred radicals through oxidative deprotonation electron transfer (ODET) or concerted proton‐coupled electron transfer (PCET) activation, respectively.…”

A Molybdenum(0) Isocyanide Analogue of Ru(2,2′‐Bipyridine)32+: A Strong Reductant for Photoredox Catalysis

“…[25] Electron transfer between photoexcited Mo(CNAr 3 NC) 3 and trans-1 produces radical intermediate A À, which can be oxidized to diradical B by Mo(CNAr 3 NC) 3 + in the electronic ground state. Initially only the trans isomer of 1 is present.…”

Ein Molybdän(0)‐Isocyanid‐Komplex als Ru(2,2′‐Bipyridin)32+‐Analogon: ein starkes Reduktionsmittel für die Photoredoxkatalyse

“…[25] Elektronentransfer von angeregtem Mo-(CNAr 3 NC) 3 zu trans-1 gibt die radikalische Zwischenstufe A À ,d ie durch die Grundzustandsspezies Mo(CNAr 3 NC) 3 + zum Diradikal B oxidiert werden kann. Zu Beginn ist lediglich das trans-Isomer von 1 vorhanden.…”

“…Zu Beginn ist lediglich das trans-Isomer von 1 vorhanden. [25] Elektronentransfer von angeregtem Mo-(CNAr 3 NC) 3 zu trans-1 gibt die radikalische Zwischenstufe A À ,d ie durch die Grundzustandsspezies Mo(CNAr 3 NC) 3 + zum Diradikal B oxidiert werden kann. [26] B kann nun entweder in einer intramolekularen Reaktion Produkt 2 bilden oder wieder Substrat 1 regenerieren, wodurch allerdings eine Mischung aus cis-u nd trans-Isomeren entsteht.…”