An Intramolecular Wittig Approach toward Heteroarenes: Synthesis of Pyrazoles, Isoxazoles, and Chromenone-oximes
作者:Pankaj V. Khairnar、Tsai-Hui Lung、Yi-Jung Lin、Chi-Yi Wu、Srinivasa Rao Koppolu、Athukuri Edukondalu、Praneeth Karanam、Wenwei Lin
DOI:10.1021/acs.orglett.9b01395
日期:2019.6.7
α-Halohydrazones/ketoximes are transformed into trisubstituted pyrazoles/disubstituted isoxazoles by treatment with phosphine, acyl chloride, and a base. Mechanistic investigations revealed the in situ formation of azo/nitroso olefin intermediates which underwent a tandem phospha-Michael/N- or O-acylation/intramolecular Wittig reaction to afford the heteroarenes in moderate to good yields. Further
Transition-Metal-Free<i>N</i>-Arylation of Pyrazoles with Diaryliodonium Salts
作者:Zsombor Gonda、Zoltán Novák
DOI:10.1002/chem.201502995
日期:2015.11.16
developed for the N‐arylation of pyrazoles using diaryliodoniumsalts. The transformation does not require any transition‐metal catalyst and provides the desired N‐arylpyrazoles rapidly under mild reaction condition in the presence of aqueous ammonia solution as a mild base without the use of inert atmosphere. The chemoselectivity of unsymmetric diaryliodoniumsalts was also explored with large number
PTSA-catalyzed Mannich-type–cyclization–oxidation tandem reactions: one-pot synthesis of 1,3,5-substituted pyrazoles from aldehydes, hydrazines and alkynes
作者:Pei Liu、Ying-Ming Pan、Yan-Li Xu、Heng-Shan Wang
DOI:10.1039/c2ob25487e
日期:——
A convenient one-pot Mannich-type–cyclization–oxidation tandem process has been developed for the synthesis of 1,3,5-trisubstituted pyrazoles derivatives fromaldehydes, hydrazines and alkynes using p-toluenesulfonic acid monohydrate (PTSA) as a multifunctional catalyst. This method provides a flexible and rapid route to 1,3,5-trisubstituted pyrazoles.
A novel one-pot synthesis of substituted pyrazoles from chalcones and hydrazines via a tandem cyclization-dehydrogenation approach is described. This process is based on the use of a bifunctional noble-metal/solid-acid catalyst, Pd/C/K-10 montmorillonite and microwave irradiation under solvent-free conditions. The cyclization of chalcones with hydrazines readily takes place on the strong solid acid while the presence of the metal ensures the formation of the aromatic product through dehydrogenation. The reactions are complete in 30 minutes providing good yields and high selectivities.
Provided is an organic electroluminescent device which is suitable for use in full-color and multicolor panels and shows higher luminous efficiency and better driving stability than organic electroluminescent devices utilizing luminescence from the singlet state. The organic electroluminescent device comprises a substrate
1
and an anode
2
, organic layers, and a cathode
8
piled one upon another on the substrate, at least one of the organic layers comprises a light-emitting layer
5
containing a host material and a dopant material, and a compound having 2 to 4 pyrazole structures represented by the following formula I (wherein Ar
4
to Ar
6
are independently hydrogen or substituted or unsubstituted aromatic hydrocarbon groups or aromatic heterocyclic groups) is used as said host material.