Cobalt-Catalyzed Oxidative Isocyanide Insertion to Amine-Based Bisnucleophiles: Diverse Synthesis of Substituted 2-Aminobenzimidazoles, 2-Aminobenzothiazoles, and 2-Aminobenzoxazoles
作者:Tong-Hao Zhu、Shun-Yi Wang、Gao-Nan Wang、Shun-Jun Ji
DOI:10.1002/chem.201300239
日期:2013.5.3
Cobalt catalysis: Synthesis of substituted 2‐aminobenzimidazoles, 2‐aminobenzothiazoles, and 2‐aminobenzoxazoles was achieved by using cobalt(II) acetate catalyzed isocyanideinsertion to o‐diaminobenzene, 2‐aminobenzenethiol, and 2‐aminophenol derivatives in 1,4‐dioxane (see scheme). It was found that the reaction proceeded efficiently to give the desired products in up to 95 % isolated yields by
A Pd-catalyzed aerobic oxidation of o-aminophenols and isocyanides for the synthesis of 2-aminobenzoxazoles and 3-aminobenzoxazines has been achieved in an air atmosphere. The procedure constructs 2-aminobenzoxazoles and 3-aminobenzoxazines with moderate to excellent yields and a broad substrate scope. Apart from experimental simplicity, this methodology has the advantages of mild reaction conditions and easily accessible starting materials. Furthermore, the utility of this method has also been successfully applied to the synthesis of other types of useful nitrogen heterocycles.
Cobalt(II)-Catalyzed Isocyanide Insertion Reaction with Amines under Ultrasonic Conditions: A Divergent Synthesis of Ureas, Thioureas and Azaheterocycles
作者:Tong-Hao Zhu、Xiao-Ping Xu、Jia-Jia Cao、Tian-Qi Wei、Shun-Yi Wang、Shun-Jun Ji
DOI:10.1002/adsc.201300745
日期:2014.2.10
AbstractCobalt(II) acetylacetonate‐catalyzed isocyanide insertion reactions with amines utilizing tert‐butyl hydroperoxide (TBHP) as an oxidant under ultrasound conditions have been developed, which lead to the synthesis of ureas, thioureas, as well as 2‐aminobenzimidazoles, 2‐aminobenzothiazoles, and 2‐aminobenzoxazoles under the general reaction conditions in up to 96% yields, respectively. The intermediate amino methylidyneaminiums, initiated by cobalt(II) acetylacetonate‐catalyzed reactions of isocyanides with amines, could be easily trapped by different nucleophiles such as water, sulfur, and intramolecular nucleophilic functional groups. This method provides a simple, general and practical protocol for the divergent synthesis of ureas, thioureas and azaheterocycles.magnified image