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.
dithiocarbamates and tetramethylthiuram disulfide (TMTD), respectively. With the promotion of NaH/CuI, the reaction of o-aminophenols with dithiocarbamates gave 2-aminobenzoxazoles with good yield (70–92%) in one pot manner, and 2-mercaptobenzoxazoles were synthesized (yield: 55–80%) in the presence of K2CO3 by treating o-aminophenols with tetramethylthiuram disulfide (TMTD). The feature of this method
Going to the source: Formamides or parentamines were used as an aminogroupsource for the silver‐mediated amination of benzoxazoles. Although reactions with formamides proceeded at high temperatures, the directamination with amines took place under much milder conditions (see scheme). Optically active aminogroups could also be installed without racemization.
catalysis of copper, 2-aminophenols or 2-aminothiophenols reacted with thiocarbamoyl chlorides via a tandem manner, furnishing a series of 17 benzoheterocycles smoothly with good to excellent yields (70–91%). The broad substrate scope, short reaction time, mild react conditions, easy performance and nice yields make this approach attractive, showing its practical synthetic value for the preparation of some
Transition metal-free direct amination of benzoxazoles using formamides as nitrogen sources
作者:Rui Wang、Hong Liu、Liang Yue、Xiao-ke Zhang、Qiu-yuan Tan、Ruo-lin Pan
DOI:10.1016/j.tetlet.2014.02.070
日期:2014.4
A transition metal-free method for the directamination of benzoxazoles using formamides as nitrogen sources is reported, which was mediated by an inexpensive and environmentally friendly tetrabutylammonium iodide/tert-butyl hydroperoxide system and gave the 2-aminobenzoxazole derivatives with moderate to good yields.