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
Bu<sub>4</sub>NI-catalyzed, oxidative C<sub>(sp2)</sub>–C<sub>(sp3)</sub> cross dehydrogenative coupling for the regioselective direct C-3 benzylation of 2<i>H</i>-indazoles
作者:Lalit Yadav、Sandeep Chaudhary
DOI:10.1039/d0ob01282c
日期:——
A Bu4NI-catalyzed, DTBP-promoted, regioselective C(sp2)–C(sp3) cross dehydrogenative coupling (CDC) protocol for the direct C-3 benzylation of 2H-indazoles is reported. The metal-free protocol is operationally simple and proceeds mechanistically via the generation of stable benzylic free-radicals followed by regioselective addition at the C-3 position of 2H-indazoles which afforded C-3 benzylated 2H-indazoles
报道了一种 Bu 4 NI 催化、DTBP 促进的区域选择性 C (sp 2 ) -C (sp 3 )交叉脱氢偶联 (CDC) 方案,用于 2 H-吲唑的直接 C-3 苄基化。无金属方案操作简单,通过产生稳定的苄基自由基,然后在 2 H-吲唑的 C-3 位置进行区域选择性加成,得到 C-3 苄基化的2H-吲唑的产率高达 87%。该方法显示出一系列不同的官能团耐受性和广泛的底物兼容性。克级合成进一步突出了这种方法的重要性和通用性。
A General One-Pot Synthesis of 2<i>H</i>
-Indazoles Using an Organophosphorus-Silane System
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
A general and practical regioselective approach for the C–H amination of 2H-indazoles under transition-metal-free conditions was developed. A series of substrates were tested showing eminent functional group tolerance and affording the C–N functionalization products in good to excellent yields. Mechanism studies revealed that a radical process was involved in this transformation.
A facile synthesis of 2H-indazoles under neat conditions and further transformation into aza-γ-carboline alkaloid analogues in a tandem one-pot fashion
作者:Shinde Vidyacharan、A. Sagar、N. C. Chaitra、Duddu S. Sharada
DOI:10.1039/c4ra06838f
日期:——
We have described a facile, microwave-assisted, catalyst-free and solvent-free approach to 2H-indazoles and further developed a robust tandem one-pot metal-free strategy for CâC bond formation at the C-3 position of 2H-indazoles leading to a unique class of aza-γ-carboline alkaloid analogues. This straightforward expedient synthesis constitutes an interesting alternative to the existing conventional transition metal catalyzed reactions.