271-44-3Relevant articles and documents
Orthogonal Regulation of Nucleophilic and Electrophilic Sites in Pd-Catalyzed Regiodivergent Couplings between Indazoles and Isoprene
Jiang, Wen-Shuang,Ji, Ding-Wei,Zhang, Wei-Song,Zhang, Gong,Min, Xiang-Ting,Hu, Yan-Cheng,Jiang, Xu-Liang,Chen, Qing-An
, p. 8321 - 8328 (2021)
Depending on the reactant property and reaction mechanism, one major regioisomer can be favored in a reaction that involves multiple active sites. Herein, an orthogonal regulation of nucleophilic and electrophilic sites in the regiodivergent hydroamination of isoprene with indazoles is demonstrated. Under Pd-hydride catalysis, the 1,2- or 4,3-insertion pathway with respect to the electrophilic sites on isoprene could be controlled by the choice of ligands. In terms of the nucleophilic sites on indazoles, the reaction occurs at either the N1- or N2-position of indazoles is governed by the acid co-catalysts. Preliminary experimental studies have been performed to rationalize the mechanism and regioselectivity. This study not only contributes a practical tool for selective functionalization of isoprene, but also provides a guide to manipulate the regioselectivity for the N-functionalization of indazoles.
Studies on synthetic approaches to 1H- and 2H-indazolyl derivatives
Isin,De Jonge,Castagnoli Jr.
, p. 4220 - 4226 (2001)
Synthetic approaches designed to provide 1H- and 2H-indazolyl derivatives of potential biological interest are reported. Special emphasis has been placed on the characterization of indazolylpyridinium products generated from reactions between indazole and 4-chloro-1-methylpyridinium iodide under various conditions. A stable mixture consisting of 3 parts of the 1H-isomer 9 to 1 part of the 2H-isomer 10 was obtained at room temperature in the presence of the base 2,2,6,6-tetramethylpiperidine (TMP). The same reaction at 60 °C gave only the 1H-isomer 9. At 100 °C in the absence of TMP only the 2H-isomer 10 was formed. The isomerization of 10 to 9 was found to proceed quantitatively at 60 °C but only in the presence of TMP. The effects of temperature and base on the course of these reactions are rationalized in terms of kinetic and thermodynamic parameters.
Regioselective N-alkylation of the 1H-indazole scaffold; ring substituent and N-alkylating reagent effects on regioisomeric distribution
Alam, Ryan M.,Keating, John J.
supporting information, p. 1939 - 1951 (2021/08/23)
The indazole scaffold represents a promising pharmacophore, commonly incorporated in a variety of therapeutic drugs. Although indazole-containing drugs are frequently marketed as the corresponding N-alkyl 1H- or 2H-indazole derivative, the efficient synthesis and isolation of the desired N-1 or N-2 alkylindazole regioisomer can often be challenging and adversely affect product yield. Thus, as part of a broader study focusing on the synthesis of bioactive indazole derivatives, we aimed to develop a regioselective protocol for the synthesis of N-1 alkylindazoles. Initial screening of various conditions revealed that the combination of sodium hydride (NaH) in tetrahydrofuran (THF) (in the presence of an alkyl bromide), represented a promising system for N-1 selective indazole alkylation. For example, among fourteen C-3 substituted indazoles examined, we observed > 99% N-1 regioselectivity for 3-carboxymethyl, 3-tert-butyl, 3-COMe, and 3-carboxamide indazoles. Further extension of this optimized (NaH in THF) protocol to various C-3, -4, -5, -6, and -7 substituted indazoles has highlighted the impact of steric and electronic effects on N-1/N-2 regioisomeric distribution. For example, employing C-7 NO2 or CO2Me substituted indazoles conferred excellent N-2 regioselectivity (≥ 96%). Importantly, we show that this optimized N-alkylation procedure tolerates a wide structural variety of alkylating reagents, including primary alkyl halide and secondary alkyl tosylate electrophiles, while maintaining a high degree of N-1 regioselectivity.
A novel copper-catalyzed, hydrazine-free synthesis of N-1 unsubstituted 1H-indazoles using stable guanylhydrazone salts as substrates
Rekowski, Szymon P.,Kroener, Bettina K.,Kathuria, Deepika,Wani, Aabid A.,Chourasiya, Sumit S.,Conrad, Jürgen,Bharatam, Prasad V.,Frey, Wolfgang,Beifuss, Uwe
, (2021/06/12)
A CuI-catalyzed, hydrazine-free transformation of 2-(2-bromoarylidene)guanylhydrazone hydrochlorides using Cs2CO3 as a base and DMEDA as a ligand at 120 °C for 5 h delivers substituted 1H-indazoles with yields up to 75%. The C,N double bond configuration of the substrates was determined by NMR experiments and quantum chemical calculations. The reaction mechanism was studied using quantum chemical calculations.
Synthesis of indazoles from 2-formylphenylboronic acids
Jirgensons, Aigars,Seins, Alberts,Solomin, Vitalii V.
, p. 22710 - 22714 (2021/07/21)
A method for the synthesis of indazoles was developed which involves a copper(ii) acetate catalysed reaction of 2-formylboronic acids with diazadicaboxylates followed by acid or base induced ring closure. Hydrazine dicarboxylates were also shown as competent reaction partners for the synthesis of indazoles, however, they required a stoichiometric amount of copper(ii) acetate for the C-N bond formation step. The transformation can be efficiently performed as a two step-one pot procedure to give a range of 1N-alkoxycarbonyl indazoles.
NovelN-transfer reagent for converting α-amino acid derivatives to α-diazo compounds
Lu, Guan-Han,Huang, Tzu-Chia,Hsueh, Hsiao-Chin,Yang, Shin-Cherng,Cho, Ting-Wei,Chou, Ho-Hsuan
supporting information, p. 4839 - 4842 (2021/05/25)
A novel universalN-transfer reagent for direct and effective transformation of α-amino ketones, acetamides, and esters to the corresponding α-diazo products under mild basic conditions has been developed. This one-step synthetic approach not only allows for generation of α-substituted-α-diazo carbonyl compounds from α-amino acid derivatives but also permits preparation of α-diazo dipeptides fromN-terminal dipeptides (32 examples, up to 91%).
Visible-Light-Mediated N-Desulfonylation of N-Heterocycles Using a Heteroleptic Copper(I) Complex as a Photocatalyst
Hunter, Cameron J.,Boyd, Michael J.,May, Gregory D.,Fimognari, Robert
, p. 8732 - 8739 (2020/07/16)
A photoredox protocol that uses a heteroleptic Cu (I) complex, [Cu(dq)(BINAP)]BF4, has been developed for the photodeprotection of benzenesulfonyl-protected N-heterocycles. A range of substrates was examined, including indazoles, indoles, pyrazoles, and benzimidazole, featuring both electron-rich and electron-deficient substituents, giving good yields of the N-heterocycle products with broad functional group tolerance. This transformation was also found to be amenable to flow reaction conditions.
Ru(II)-Catalyzed C-H Hydroxyalkylation and Mitsunobu Cyclization of N-Aryl Phthalazinones
Ghosh, Prithwish,Han, Sang Hoon,Jeoung, Daeun,Kim, In Su,Kim, Kunyoung,Kim, Saegun,Kim, Seung Jun,Ku, Jin-Mo,Mishra, Neeraj Kumar
, p. 2520 - 2531 (2020/03/13)
Ruthenium(II)-catalyzed C(sp2)-H functionalization of N-Aryl phthalazinones with a range of aldehydes and activated ketone is described. Initial formation of hydroxyalkylated phthalazinones and subsequent Mitsunobu cyclization provided facile access to biologically relevant indazolophthalazinones. The utility of this method is highlighted by synthetic transformations into a series of potentially bioactive scaffolds.
Catalytic Reductions Without External Hydrogen Gas: Broad Scope Hydrogenations with Tetrahydroxydiboron and a Tertiary Amine
Korvinson, Kirill A.,Akula, Hari K.,Malinchak, Casina T.,Sebastian, Dellamol,Wei, Wei,Khandaker, Tashrique A.,Andrzejewska, Magdalena R.,Zajc, Barbara,Lakshman, Mahesh K.
supporting information, p. 166 - 176 (2020/01/02)
Facile reduction of aryl halides with a combination of 5% Pd/C, B2(OH)4, and 4-methylmorpholine is reported. Aryl bromides, iodides, and chlorides were efficiently reduced. Aryl dihalides containing two different halogen atoms underwent selective reduction: I over Br and Cl, and Br over Cl. Beyond these, aryl triflates were efficiently reduced. This combination was broadly general, effectuating reductions of benzylic halides and ethers, alkenes, alkynes, aldehydes, and azides, as well as for N-Cbz deprotection. A cyano group was unaffected, but a nitro group and a ketone underwent reduction to a low extent. When B2(OD)4 was used for aryl halide reduction, a significant amount of deuteriation occurred. However, H atom incorporation competed and increased in slower reactions. 4-Methylmorpholine was identified as a possible source of H atoms in this, but a combination of only 4-methylmorpholine and Pd/C did not result in reduction. Hydrogen gas has been observed to form with this reagent combination. Experiments aimed at understanding the chemistry led to the proposal of a plausible mechanism and to the identification of N,N-bis(methyl-d3)pyridin-4-amine (DMAP-d6) and B2(OD)4 as an effective combination for full aromatic deuteriation. (Figure presented.).
A NaH-promoted N-detosylation reaction of diverse p-toluenesulfonamides
Sun, Wanwan,Chen, Xiaobei,Hu, Ying,Geng, Huihui,Jiang, Yuanrui,Zhou, Yuxin,Zhu, Wenjing,Hu, Min,Hu, Haohua,Wang, Xingyi,Wang, Xinli,Zhang, Shilei,Hu, Yanwei
supporting information, (2020/10/05)
A NaH-mediated detosylation reaction of various Ts-protected indoles, azaheterocycles, anilines and dibenzylamine was reported. The method features cheap reagent, convenient operations, mild reaction conditions and broad substrate scope. Moreover, this study revealed that the loading of NaH in tosylation reactions of nitrogen-containing compounds with NaH as a base in DMA or DMF should be controlled due to the possibility of adverse detosylation.
