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