hydrazine monohydrochloride readily formed pyrazoline intermediates under mild conditions. Oxidation of pyrazolines, in situ, employing bromine afforded a wide variety of pyrazoles. The methodology offers a fast, and often chromatography-free protocol for the synthesis of 3,4,5-substituted pyrazoles in good to excellent yields. Alternatively, a more benign oxidation protocol affords 3,5-disubstituted or
Stereoselective Direct
<i>N</i>
‐Trifluoropropenylation of Heterocycles with a Hypervalent Iodonium Reagent
作者:János T. Csenki、Ádám Mészáros、Zsombor Gonda、Zoltán Novák
DOI:10.1002/chem.202102840
日期:2021.11.11
E-selective trifluoropropenylation of versatile N-heterocycles was developed with the utilization of trifluoropropenyliodonium salts. The procedure enables the straightforward direct introduction of the trifluoroalkenyl moiety into heterocyclic scaffolds under simple and mild reaction conditions.
An iodine-catalyzed denitrative imino-diaza-Nazarov cyclization (DIDAN) methodology has been developed for the synthesis of pyrazoles with high to excellent yields by using α-nitroacetophenone derivatives and in situ generated hydrazones. The key transformation of this oxidative 4π-electrocyclization proceeds through an enamine–iminium ion intermediate. This rapid one-pot DIDAN protocol results in
The diaza-Nazarov cyclization involving a 2,3-diaza-pentadienyl cation for the synthesis of polysubstituted pyrazoles
作者:Balakrishna Aegurla、Rama Krishna Peddinti
DOI:10.1039/c7ob01949a
日期:——
diaza-Nazarov (DAN) type cyclization for the construction of substituted pyrazoles from easily available starting materials via an enamine–iminium ion intermediate is described. The oxidative cyclization worked under green conditions with remarkable regioselectivity. This one-pot, efficient and operationally simple three-component intramolecular regioselective DAN cyclization displayed a wide range of
A highly efficient heterogeneous palladium-catalyzed cascade three-component reaction of acid chlorides, terminal alkynes and hydrazines leading to pyrazoles
作者:Qiurong Chen、Fang Yao、Lin Yin、Mingzhong Cai
DOI:10.1016/j.jorganchem.2015.12.037
日期:2016.2
MCM-41-immobilized palladium(II) complex [MCM-41-2N–Pd(OAc)2] and 1.0 mol% of CuI, acid chlorides were coupled with terminal alkynes in Et3N at 50 °C to give α,β-unsaturated ynones, which were converted in situ into pyrazoles by the cycloaddition of hydrazines at room temperature with acetonitrile as cosolvent. The cascade reactions generated a variety of pyrazole derivatives in moderate to good yields, and