A new iron-catalyzed, direct C-H amination of azoles at C2 has been developed by usingformamides or amines as nitrogen sources. Imidazole is the only additive in the catalyst system and oxygen in air is employed during the transformation process.
Copper-Catalyzed Direct Amination of Benzoxazoles Using Primary Amines as Nitrogen Sources
作者:Chun Cai、Jian Gu
DOI:10.1055/s-0034-1379886
日期:——
A facile, efficient, and simple protocol for direct oxidative C–H amination of benzoxazoles with primary amines through copper-catalyzedC–H bond activation using tert -butyl peroxide (TBP) as oxidant under air has been developed. The reaction proceeds smoothly at ambient temperature to furnish the products. A variety of substituted aminobenzoxazoles were synthesized with good to excellent yields.
This protocol describes a novel, mild and convenient route to afford 2-aminobenzoxazoles in high yields, and represents a significant advance towards an environmentally friendly strategy. Aliphatic amines are made to react with carbon disulfide to provide intermediate dithiocarbamates (DTC), which in the presence of 2-aminophenol, subsequently undergo successive intermolecular nucleophilic attack and desulfurization to produce 2-aminobenzoxazoles within 3 h.
Amination of Benzoxazoles and 1,3,4-Oxadiazoles Using 2,2,6,6-Tetramethylpiperidine-N-oxoammonium Tetrafluoroborate as an Organic Oxidant
作者:Sebastian Wertz、Shintaro Kodama、Armido Studer
DOI:10.1002/anie.201104735
日期:2011.11.25
No transition metals are necessary to convert benzoxazoles and 1,3,4‐oxadiazoles into the corresponding pharmacologically interesting 2‐aminated heterocycles by formal direct C(2)‐aminationusing tetramethylpiperidine‐N‐oxoammonium tetrafluoroborate (TEMPO+BF4−) as an oxidant (see scheme; TEMP=2,2,6,6‐tetramethylpiperidine; TfOH=trifluoromethanesulfonic acid).
Metal-free synthesis of 2-aminobenzoxazoles using hypervalent iodine reagent
作者:Yogesh S. Wagh、Neelam J. Tiwari、Bhalchandra M. Bhanage
DOI:10.1016/j.tetlet.2012.12.127
日期:2013.3
A facile, simple, mild, and metal-free protocol for the synthesis of 2-aminobenzoxazoles has been developed via C–H bond amination of benzoxazoles with amines through a ring-opening and subsequent ring-closure approach. The reaction was performed in two steps wherein nucleophilic addition of amines across benzoxazoles takes place in the absence of any reagent or catalyst under solvent-free condition