Visible light induced palladium catalyzed C H hydroxylation of nitrogen-containing heterocyclic aromatics in the presence of H2O2

Synthesis of 2-(Pyridin-2-yl)phenols and 2-(Pyridin-2-yl)anilines

“…Orange solid (86 mg, 40% yield); R f = 0.60 (EtOAc/hexane = 1:2); mp 159.4–160.3 °C (lit . 100.4–101.3 °C); IR (neat): 2921, 2852, 2586, 1601, 1516, 1473, 1343, 1223, 1152, 1113, 1019, 859, 746, 667 cm –1 ; 1 H NMR (400 MHz, CDCl 3 ): δ = 13.4 (brs, 1H), 9.38 (dd, J = 2.8, 0.8 Hz, 1H), 8.60 (dd, J = 9.2, 2.8 Hz, 1H), 8.08 (dd, J = 9.2, 0.8 Hz, 1H), 7.84 (dd, J = 8.4, 1.6 Hz, 1H), 7.43 (ddd, J = 8.4, 7.2, 1.6 Hz, 1H), 7.08 (dd, J = 8.4, 1.2 Hz, 1H), 6.98 (ddd, J = 8.4, 7.2, 1.2 Hz, 1H); 13 C­{ 1 H} NMR (100 MHz, CDCl 3 ): δ = 163.0, 160.7, 142.6, 141.8, 134.0, 132.5, 127.3, 119.6, 119.3, 119.3, 117.4; HRMS (ESI positive) m / z calcd for C 11 H 9 O 3 N 2 : 217.0608 [M + H] + , found: 217.0606 [M + H] + .…”

Hydroxylation of Substituted Anilides with Metallaphotocatalysis

“…20 In 2022, orthohydroxylation of 2-arylpyridines and 2-arylbenzoxazoles has been reported by Chu and co-workers using a Pd(II) catalyst and an Eosin Y photocatalyst (EY-Na 2 ) under mild conditions (Scheme 1bii). 21 With the onset of hypervalent iodine(III) reagents being prevalently used as an oxidizing reagent in hydroxylation reactions of arenes and heteroarenes in thermal TM catalysis reactions, 7,10,15 and their increasing application in Based on this, we hypothesized that an N-pivaloyl (Piv-) group may serve as an ideal DG for the ortho-hydroxylation of substituted anilines because it is stable under reaction conditions and can readily be removed. We began our photochemical investigations with N-pivaloyl ethyl anthranilate 1a, a representative ortho-substituted aniline, and explored reaction conditions to find an optimal oxidizing reagent using [RuCl After identifying optimal reaction conditions, the direct ortho-hydroxylation of a range of anilides containing osubstituents was explored to establish the substrate scope of the catalytic reaction.…”

“…More recently, light-induced catalysis has been used in other chemical transformations beyond C–C and C–heteroatom bond-forming cross-coupling reactions due to its ability to generate reactive intermediates under mild conditions. , In 2018, Singh et al reported a metallaphotoredox method for ortho -hydroxylation of 2-arylpyridines by integrating 4CzIPN photocatalyst and Pd­(OAc) 2 as a TM metal catalyst under visible-light conditions (Scheme bi) . In 2022, ortho -hydroxylation of 2-arylpyridines and 2-arylbenzoxazoles has been reported by Chu and co-workers using a Pd­(II) catalyst and an Eosin Y photocatalyst (EY-Na 2 ) under mild conditions (Scheme bii) . With the onset of hypervalent iodine­(III) reagents being prevalently used as an oxidizing reagent in hydroxylation reactions of arenes and heteroarenes in thermal TM catalysis reactions, ,, and their increasing application in visible-light-induced organophotocatalysis, we were prompted to investigate directed ortho -hydroxylation of substituted anilides with hypervalent iodine­(III) oxidizing reagents under visible-light metallaphotocatalysis (Scheme c).…”

“… 20 In 2022, ortho -hydroxylation of 2-arylpyridines and 2-arylbenzoxazoles has been reported by Chu and co-workers using a Pd(II) catalyst and an Eosin Y photocatalyst (EY-Na 2 ) under mild conditions ( Scheme 1 bii). 21 With the onset of hypervalent iodine(III) reagents being prevalently used as an oxidizing reagent in hydroxylation reactions of arenes and heteroarenes in thermal TM catalysis reactions, 7 , 10 , 15 and their increasing application in visible-light-induced organophotocatalysis, 22 we were prompted to investigate directed ortho -hydroxylation of substituted anilides with hypervalent iodine(III) oxidizing reagents under visible-light metallaphotocatalysis ( Scheme 1 c).…”

Biomimetic design of an α-ketoacylphosphonium-based light-activated oxygenation auxiliary

“…To overcome such problems, directing group strategies that combine transition metal catalysts and suitable oxidants have been extensively studied. 11,12 Our LOA-based strategy might add a tactically different and transition metal-free protocol to the synthetic toolbox for 2-aminophenols.…”