Hydrazides in the reaction with hydroxypyrrolines: less nucleophilicity – more diversity

• Dmitrii A. Shabalin,
• Evgeniya E. Ivanova,
• Igor A. Ushakov,
• Elena Yu. Schmidt and
• Boris A. Trofimov

Beilstein J. Org. Chem. 2021, 17, 319–324, doi:10.3762/bjoc.17.29

• -pyrroline (1a) with an equimolar amount of benzohydrazide (2a) was initially performed in the presence of trifluoroacetic acid (TFA, 10 mol %) in refluxing acetonitrile for 3 h. Unexpectedly, 6-(2'-benzoylhydrazinyl)-1,4,5,6-tetrahydropyridazine 3aa was isolated in a 46% yield, while the anticipated 1,4

• -dihydropyridazine 4aa was not detected at all (Table 1, entry 1). Although the increase of the reaction time up to 5 h slightly improved the yield of tetrahydropyridazine 3aa (53%, entry 2 in Table 1), more efficient appeared to be the use of a two-fold excess of benzohydrazide (2a) that provided 3aa in 93

• (Table 1, entries 7–11). Finally, the best isolated yield of 1,4-dihydropyridazine 4aa (74%) was achieved by a two-step, one-pot protocol, comprising the initial recyclization of hydroxypyrroline 1a with 2 equiv of benzohydrazide (2a) in refluxing acetonitrile for 3 h in the presence of 10 mol % of TFA

Efficient [(NHC)Au(NTf₂)]-catalyzed hydrohydrazidation of terminal and internal alkynes

• Maximillian Heidrich and
• Herbert Plenio

Beilstein J. Org. Chem. 2020, 16, 2080–2086, doi:10.3762/bjoc.16.175

• catalysts with such ligands also display high activities in other gold-catalyzed reactions. Results and Discussion Catalyst screening: Five different [(NHC)Au(NTf2)] complexes 1, 2, 3, 4, and 5 with bulky NHC ligands were tested in the hydrohydrazidation of phenylacetylene with benzohydrazide (Scheme 2; T

• consortium chlorobenzene is a problematic solvent, whose use should be avoided [47]. We therefore performed an extensive solvent screening focusing on “greener” solvents for the reactions of benzohydrazide with either phenylacetylene or 4-methoxyphenylacetylene (Table 1). It was found that the catalytic

• anisole (20 mL). Gold-triflimide catalyst 1 (15.5 mg, 0.01 mmol, 0.2 mol %) was added and the reaction mixture was stirred at 60 °C for 24 h. The mixture was cooled to 0 °C and the formed precipitate was collected and washed with a small amount of pentane to afford N'-(1-phenylethylidene)benzohydrazide

One-pot four-component reaction for convenient synthesis of functionalized 1-benzamidospiro[indoline-3,4'-pyridines]

• Chao Wang,
• Yan-Hong Jiang and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2014, 10, 2671–2676, doi:10.3762/bjoc.10.281

• Chao Wang Yan-Hong Jiang Chao-Guo Yan College of Chemistry & Chemical Engineering Yangzhou University, Yangzhou 225002, China 10.3762/bjoc.10.281 Abstract The one-pot four-component reaction of benzohydrazide (2-picolinohydrazide), acetylenedicarboxylate, isatins and malononitrile (ethyl

• cyanoacetate) with triethylamine as base catalyst afforded functionalized 1-benzamidospiro[indoline-3,4'-pyridines] in good yields. 1H NMR spectra indicated that an equilibrium of cis/trans-conformations exist in the obtained products. Keywords: acetylenedicarboxylate; benzohydrazide; 1,4-dihydropyridine

• ], we herein wish to report the efficient synthesis of functionalized 1-benzamidospiro[indoline-3,4’-pyridines] via one-pot four-component reactions of benzohydrazide, acetylenedicarboxylate, isatin and malononitrile. Results and Discussion According to the reaction conditions of the previously reported