Photocatalytic Anti‐Markovnikov Radical Hydro‐ and Aminooxygenation of Unactivated Alkenes Tuned by Ketoxime Carbonates

Abstract

A tunable photocatalytic method is reported for anti‐Markovnikov hydro‐ and aminooxygenation of unactivated alkenes using readily accessible ketoxime carbonates as the diverse functionalization reagents. Mechanistic studies reveal that this reaction is initiated through an energy‐transfer‐promoted N−O bond homolysis of ketoxime carbonates leading to alkoxylcarbonyloxyl and iminyl radicals under visible‐light photocatalysis, followed by the addition of alkoxylcarbonyloxyl radical to alkenes. By taking advantage of the different stability of the iminyl radicals, the generated carbon radical either abstracts a hydrogen atom from the media to form the anti‐Markovnikov hydrooxygenation product, or it is trapped by the persistent iminyl radical to furnish the aminooxygenation product. Notably, this is the first example of direct hydrooxygenation of unactivated olefins with anti‐Markovnikov regioselectivity involving an oxygen‐centered radical.

Synthesis of γ-amino acids via photocatalyzed intermolecular carboimination of alkenes

“…Control experiments have demonstrated that both the photosensitizer and visible light were essential for this carboimination reaction. Based on these experimental results and previous reports, 10–12,19 a plausible energy transfer-driven catalytic cycle is outlined in Fig. 3.…”

“…Based on recent works from the groups of Glorius, 10 Cho, 11 Han 12 and Xia 13 on the use of oxime esters as the source of N-centred diaryliminyl radicals, we hypothesized whether or not such a method could be used to synthesize γ-amino acid Schiff bases (Fig. 1c).…”

Efficient access to β-amino acid ester/β-amino ketone derivatives via photocatalytic radical alkoxycabonylimidation/carbonylimidation of alkenes

“…12 Han's group achieved the anti-Markovnikov hydrooxygenation and aminooxygenation of inactivated alkenes by tuning the structure of oxime carbonates. 13 They obtained alkoxylcarbonyloxyl and iminyl radicals as the key intermediates generated from oxime carbonates. Huo, Bao and Yuan's group carried out an intermolecular two-component regioselective alkene-oxyimination reaction using easily available aryl carboxylic-acid oxime esters as bifunctional agents, thereby producing aryl carboxyl and iminyl radicals.…”

Hydroesterification and Difunctionalization of Olefins with N-Hydroxyphthalimide Esters

“…1 We postulated that N-(acyloxy)phthalimides (1) might be coaxed into adding to olefins wherein visible light irradiation might provide the driving force to overcome thermodynamic limitations of direct hydration-type reactions. 2 Alkyl N-(acyloxy)phthalimides have traditionally been used as acylating reagents. Pioneering studies from Okada and Odo revealed their propensity to undergo one-electron reduction, followed by N−O bond fragmentation to release alkyl radicals following decarboxylation.…”

“…Oxymercuration/reduction, hydroboration/oxidation, and Wacker oxidation/reduction can provide alcohols and ethers with varying levels of regiocontrol and efficiency . We postulated that N -(acyloxy)­phthalimides ( 1 ) might be coaxed into adding to olefins wherein visible light irradiation might provide the driving force to overcome thermodynamic limitations of direct hydration-type reactions …”