A new regiospecific synthesis method of 1H-pyrazolo[3,4-b] quinoxalines - Potential materials for organic optoelectronic devices, and a revision of an old scheme

作者：Danel Andrzej^*; Wojtasik Katarzyna; Szlachcic Pawel^*; Gryl Marlena; Stadnicka Katarzyna

来源：Tetrahedron, 2017, 73(34): 5072-5081.

DOI：10.1016/j.tet.2017.06.061

• 1H-pyrazolo[3,4-b]quinoxaline
• Palladium aminoarylation
• Reductive cyclization
• Ferrous oxalate
• Cadogan synthesis
• X-ray crystallography

A series of 6-substituted-1,3-dipheny1-1H-pyrazolo[3,4-b]quinoxalines were prepared using a new synthetic pathway: reductive cyclization of appropriate 5-(o-nitrophenyl)-pyrazoles with ferrous oxalate or triphenylphosphine. The main advantage of this procedure is that, contrary to the older protocols of pyrazolo[3,4-b]quinoxaline synthesis, this method allows for a substituent to be introduced to the carbocyclic ring without the formation of isomers. The pyrazole ring can also be modified to some extent. Furthermore, we propose a new mechanism for the oldest reported pyrazolo[3,4-b]quinoxaline synthesis, based on the condensation between o-phenylenediamine and 3,4-pyrazolin-5-diones.

• 出版日期2017-8-24