Rh(III)-catalyzed [4 + 1]-annulation of azobenzenes with α- carbonyl sulfoxonium ylides toward 3-acyl-(2H)-indazoles
作者:Jiawei Zhu、Song Sun、Jiang Cheng
DOI:10.1016/j.tetlet.2018.05.001
日期:2018.6
A Rh(III)-catalyzed [4 + 1]-annulation of azobenzenes with α- carbonylsulfoxoniumylides was developed to access 2H-indazoles in moderate to excellent yields with good functional group compatibilities. It proceeded with the sequential insertion of the Rh(III) carbene to the C−H bond and cyclization steps, where sulfoxoniumylides served as efficient and stable carbene precursor.
Silver-catalyzed [3+2]-cycloaddition of benzynes with diazocarbonyl species via a postulated (1H-indazol-1-yl)silver intermediate
作者:Chiou-Dong Wang、Rai-Shung Liu
DOI:10.1039/c2ob26760h
日期:——
We reported a new synthesis of 2-aryl-2H-indazoles via a silver-catalyzed [3+2]-cycloaddition of benzynes with diazocarbonyl reagents. We postulate that this transformation involves the generation of (1H-indazol-1-yl)silver to activate a subsequent arylation with the second benzyne.
A direct coupling of 2H-indazoles' C3 position and acyl groups has been achieved to produce 3-acyl-2H-indazoles. The Ni(ii)-catalyzed acylation might proceed through a radical pathway for the reaction of 2H-indazoles with either aryl or alkyl aldehydes in the presence of the free radical initiator TBHP and additive PivOH. This method provided a superior approach to fulfil the direct C3-acylation of