A Biphilic Phosphetane Catalyzes N–N Bond-Forming Cadogan Heterocyclization via P<sup>III</sup>/P<sup>V</sup>═O Redox Cycling
作者:Trevor V. Nykaza、Tyler S. Harrison、Avipsa Ghosh、Rachel A. Putnik、Alexander T. Radosevich
DOI:10.1021/jacs.7b03260
日期:2017.5.24
chemoselective catalytic synthesis of 2H-indazoles, 2H-benzotriazoles, and related fused heterocyclic systems with good functional group compatibility. On the basis of both stoichiometric and catalytic mechanistic experiments, the reaction is proposed to proceed via catalytic PIII/PV═O cycling, where DFT modeling suggests a turnover-limiting (3+1) cheletropic addition between the phosphetane catalyst and nitroarene
A simple and direct approach for the regioselective construction of the privileged 2H‐indazole scaffold is described. The developed one‐pot strategy involves phospholene‐mediated N−N bond formation to access 2H‐indazoles. The amount of organophosphorus reagent was minimized by recycling the phospholene oxide with organosilane reductants. Starting from functionalized 2‐nitrobenzaldehydes and primary
Microwave-assisted Cadogan reaction for the synthesis of 2-aryl-2<i>H</i>-indazoles, 2-aryl-1<i>H</i>-benzimidazoles, 2-carbonylindoles, carbazole, and phenazine
mixed with triethylphosphite or triphenylphosphine and irradiated with microwaves for several minutes at a specific power to give the desired products. The indazoles were prepared by irradiating N‐(2‐nitrobenzylidene) anilines with triethylphosphite at 200 W for 12–14 min to give 85–92% product yields. Irradiation of the mixture of N‐benzylidene‐2‐nitroanilines and triphenylphosphine at 200 W for
A rhodium-catalyzed alcohol-mediated ortho-functionalization of 2-aryl-2H-indazoles through sequential C-H activation and carbenoid insertion with diazotized Meldrum's acid was developed. Using the 2H-indazole as the directing group and alcohol as the alkyl source, a series of ortho-alkylated aryl-2H-indazoles were obtained over a wide structural scope with high site-selectivity and excellent functional-group
Mo(VI)-catalyzed Synthesis of 2-Aryl-2<i>H</i>-indazoles Using Pinacol Mediated Deoxygenation of Nitroaromatics
作者:Dhananjaya Kaldhi、Raghuram Gujjarappa、Nagaraju Vodnala、Arup K. Kabi、Nayyef Aljaar、Chandi C. Malakar
DOI:10.1246/cl.190490
日期:2019.10.5
A molybdenum(VI)-catalyzed protocol for the synthesis of 2-aryl-2H-indazoles using pinacol as a reducing agent under neat reaction conditions has been demonstrated. The developed method gives an easy access to a wide range of 2-aryl-2H-indazoles in excellent yields. The present strategy excludes the use of P(III)-reagents as deoxygenating agents.