A scalable approach to diaminopyrazoles using flow chemistry
摘要:
This Letter reports on how the combination of microwave and continuous flow chemistry facilitated the convenient preparation of aminopyrazoles from commercial aryl halides. The method was applied to a variety of substrates with good to excellent yields and further extended toward the complete flow synthesis of 5,7-dimethyl-3-phenylpyrazolo[1,5-a]pyrimidin-2-amine. (c) 2012 Elsevier Ltd. All rights reserved.
Copper Catalyzed Oxidative Arylation of Tertiary Carbon Centers
作者:Prakash Basnet、Melissa B. Sebold、Charles E. Hendrick、Marisa C. Kozlowski
DOI:10.1021/acs.orglett.0c03581
日期:2020.12.18
describe herein a Cu(OTf)2catalyzedoxidative arylation of a tertiary carbon-containing substrate including aryl malononitriles, 3-aryl benzofuran-2-ones, and 3-aryl oxindoles. In some cases, the nitrile groups of the aryl malononitriles undergo further reactions leading to lactones or imines. These reaction conditions are applicable for a range of arenes, including phenols, anilines, anisoles, and heteroarenes
A simply catalytic system containing palladium-phosphine complex, generated in situ from PdCl2/tert-phosphino ligand in pyridine, has been systematically studied in the cross-coupling of bromobenzene with malononitrile or ethyl cyanoacetate anion. The effect of molar ratio of phosphine ligand to PdCl2 on the activity of the coupling was also discussed. It is found that the catalytic system has highly catalytic activity to produce aryl malononitriles and cyanoacetates in considerable yields (67-90%) when the substituted aryl bromides were used as substrates.
A highly efficient catalytic system for cross-coupling of aryl chlorides and bromides with malononitrile anion by palladium carbene complexesElectronic supplementary information (ESI) available: experimental details. See http://www.rsc.org/suppdata/cc/b3/b302890a/
Six imidazolium chlorides (1–6) as precursors of 1,3-diaryl substituted N-heterocyclic carbene ligands were synthesized and evaluated in palladium-catalyzed cross-coupling reactions of aryl chlorides and bromides with malononitrile in the presence of NaH. Among them, 1,3-bis(2,4,6-triethylphenyl)imidazolium chloride (5) and 1,3-bis(2,4,6-triisopropylphenyl)imidazolium chloride (6) are novel. The catalytic system combining Pd(0) with imidazolium salts 4, 5 and 6 with bulky aryl groups in pyridine is found to be superior over others and afforded α-arylmalononitriles in high yields when employing a wide variety of substrates.