Base metal-catalyzed benzylic oxidation of (aryl)(heteroaryl)methanes with molecular oxygen

• Hans Sterckx,
• Johan De Houwer,
• Carl Mensch,
• Wouter Herrebout,
• Kourosch Abbaspour Tehrani and
• Bert U. W. Maes

Beilstein J. Org. Chem. 2016, 12, 144–153, doi:10.3762/bjoc.12.16

• conditions. Oxidations of this kind using Oxone® [10][11], NaOCl [12] or especially peroxides [13][14][15][16][17][18][19] as the terminal oxidant are quite numerous. However, transformations using molecular oxygen are rare. Ishii showed that organocatalysts such as N-hydroxyphthalimide (NHPI) in combination

Copper-catalyzed aminooxygenation of styrenes with N-fluorobenzenesulfonimide and N-hydroxyphthalimide derivatives

• Yan Li,
• Xue Zhou,
• Guangfan Zheng and
• Qian Zhang

Beilstein J. Org. Chem. 2015, 11, 2721–2726, doi:10.3762/bjoc.11.293

• amination of allenes [46]. Encouraged by these results, we try to develop copper-catalyzed aminooxygenation of alkenes by using NFSI. Herein, we report a simple and efficient copper-catalyzed three-component aminooxygenation reaction of styrenes with NFSI and N-hydroxyphthalimide (NHPI) derivatives (Scheme

•  1). Initially, we conducted the three-component amnooxygenation of styrene 1a with NFSI and NHPI (2a). After the reaction of 1a (0.3 mmol), NFSI (0.3 mmol, 1.0 equiv) and 2a (0.45 mmol, 1.5 equiv) was performed in the presence of Cu(OTf)2 (10 mol %) in dichloromethane (DCM, 2 mL) under nitrogen

• underwent smoothly, providing the corresponding products 3m (51%) and 3n (53%). The trans-β-methylstyrene (1o) afforded the desired product 3o in a low yield (15%). In addition, NHPI derivatives 2b and 2c were suitable nitrogen sources and the desired 3p and 3q were obtained in 56% and 64%, respectively

C–H bond halogenation catalyzed or mediated by copper: an overview

• Wenyan Hao and
• Yunyun Liu

Beilstein J. Org. Chem. 2015, 11, 2132–2144, doi:10.3762/bjoc.11.230

• a catalytic system consisting of (BPMED)CuI (copper(I) bisimine complex), N-hydroxyphthalimide (NHPI), KB(C6F5)4 and KI. The protocol allowed the selective fluorination of various substrates, including cycloalkanes and benzylic compounds using commercially available Selectfluor as fluorine source

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

• Igor B. Krylov,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

Metal-free aerobic oxidations mediated by N-hydroxyphthalimide. A concise review

• Lucio Melone and
• Carlo Punta

Beilstein J. Org. Chem. 2013, 9, 1296–1310, doi:10.3762/bjoc.9.146

• detrimental for the selectivity of the process and they would not meet the standards of “green chemistry”. An alternative catalytic route is based on the use of N-hydroxy imides (NHIs), and in particular N-hydroxyphthalimide (NHPI), which have found ample application as ideal catalysts for the aerobic

• oxidation of organic substrates [7][8][9][10][11]. NHPI acts as a precursor of the phthalimide N-oxyl (PINO) radical, which is the effective catalyst promoting hydrogen-abstraction processes (Scheme 1). The reactivity of NHPI and PINO is related to the bond dissociation energy (BDE) of the O–H group, which

• , NHPI also behaves as a relatively good hydrogen donor even at low temperatures (kH = 7.2 × 103 M−1s−1) [12], trapping peroxyl radicals before they undergo termination. PINO generation represents the key step of the overall process. Many transition metal salts and complexes have been successfully used

Copper-catalyzed aerobic aliphatic C–H oxygenation with hydroperoxides

• Pei Chui Too,
• Ya Lin Tnay and
• Shunsuke Chiba

Beilstein J. Org. Chem. 2013, 9, 1217–1225, doi:10.3762/bjoc.9.138

• weak bond-dissociation enthalpies (i.e., tertiary alkyl C–H bonds, benzylic C–H bonds, etc.), by phthalimide N-oxyl radicals generated oxidatively from N-hydroxyphthalimide (NHPI), has been reported [20][21][22]. The resulting C-radicals could be trapped with molecular oxygen to form hydroperoxides. It

• tertiary C–H bond (marked in green) was treated with the catalytic system of CuCl-1,10-phen (20 mol %) with NHPI in benzene/MeCN solvent under an O2 atmosphere (1 atm) (Scheme 7). The reaction with 20 mol % of NHPI proceeded as expected at 50 °C to afford a mixture of lactol 2i and 1,4-diols 3i in 29% and

• 3% yields, respectively, via the desired 1,4-dioxygenation, while benzophenone (7b) was also formed in 30% yield through fragmentation of the transient alkoxy radical (Scheme 4). Use of 40 mol % of NHPI slightly improved the yields of 1,4-dioxygenation products 2i and 3i (40% and 4% yields