An Efficient One-Pot Synthesis of 3,5-Diaryl-4-bromopyrazoles by 1,3-Dipolar Cycloaddition of In Situ Generated Diazo Compounds and 1-Bromoalk-1-ynes
摘要:
A simple, highly efficient, one-pot synthesis of 3,5-diaryl-4-bromopyrazoles via 1,3-dipolar cycloaddition of diazo compounds and alkynyl bromides has been developed. The diazo compounds and alkynyl bromides were generated in situ from tosylhydrazones and gem-dibromoalkenes, respectively. When ketone-derived hydrazones were used, 3,5-diaryl-4-bromo-3H-pyrazoles were obtained and the isomerization products 3,5-diaryl-4-bromo-1H-pyrazoles were formed when using aldehyde-derived hydrazones. The reaction system exhibited high regioselectivity and good functional group tolerance. Both electron-rich and electron-deficient substituents on the aromatic ring of the hydrazones or the gem-dibromoalkenes gave desired products in moderate to good yields (67-86%).
A Simplified Protocol for the Stereospecific Nickel-Catalyzed C–S Vinylation Using NiX2 Salts and Alkyl Phosphites
作者:Austin D. Marchese、Bijan Mirabi、Egor M. Larin、Mark Lautens
DOI:10.1055/s-0039-1690717
日期:2020.1
A Ni-catalyzed C–S cross-coupling using only NiI2 (0.5–2.5 mol%) and P(OiPr)3 (2.0–10.0 mol%) is reported. Using an air-stable Ni(II) precatalyst, and a cheap and commercially available ligand, a scalable and robust method was developed to cross-couple various thiophenols and styryl bromides, including some sterically encumbered thiols, an α-bromocinnamaldehyde as well as a thiolation-cyclization.
据报道,仅使用NiI 2(0.5–2.5 mol%)和P(O i Pr)3(2.0–10.0 mol%)的Ni催化的C–S交叉偶联。使用空气稳定的Ni(II)预催化剂和便宜的市售配体,开发了一种可扩展且稳健的方法来交叉偶联各种硫酚和苯乙烯基溴化物,包括一些空间受限的硫醇,α-溴肉桂醛和硫醇化环化。
Nickel‐Catalyzed, Regio‐ and Enantioselective Benzylic Alkenylation of Olefins with Alkenyl Bromide
作者:Jiandong Liu、Hegui Gong、Shaolin Zhu
DOI:10.1002/anie.202012614
日期:2021.2.19
A NiH‐catalyzed migratory hydroalkenylation reaction of olefins with alkenyl bromides has been developed, affording benzylic alkenylation products with high yields and excellent chemoselectivity. The mild conditions of the reaction preclude olefinic products from undergoing further isomerization or subsequent alkenylation. Catalytic enantioselective hydroalkenylation of styrenes was achieved by using
Silver-catalyzed Double Decarboxylative Radical Alkynylation/Annulation of Arylpropiolic Acids with α-keto Acids: Access to Ynones and Flavones under Mild Conditions
Ynones are privileged buildingblocks in various organic syntheses of heterocyclicderivatives due to their multifunctional nature, and flavones are an important class of natural products with a wide range of biological activities. We describe the catalytic double decarboxylative alkynylation of arylpropiolic acids with α‐keto acids. With Ag(I)/persulfate as the catalysis system, the valuable ynones
Iron-Catalyzed Reductive Vinylation of Tertiary Alkyl Oxalates with Activated Vinyl Halides
作者:Yang Ye、Haifeng Chen、Ken Yao、Hegui Gong
DOI:10.1021/acs.orglett.0c00561
日期:2020.3.6
of vinylated allcarbonquaternary centers via Fe-catalyzed cross-electrophile coupling of vinyl halides with tertiary alkyl methyl oxalates. The reaction displays excellent functional group tolerance and broad substrate scope, which allows cascade radical cyclization and vinylation to afford complex bicyclic and spiral structural motifs. The reaction proceeds via tertiary alkyl radicals, and the putative