A new class of pyrazolopyridine nucleus with fluorescent properties, obtained through either a radical or a Pd arylation pathway from N-azinylpyridinium N-aminides

J Org Chem. 2008 Nov 21;73(22):8800-7. doi: 10.1021/jo801549u. Epub 2008 Oct 21.

Abstract

The synthesis of dipyridopyrazole and pyridopyrazolopyrazine derivatives--both of which incorporate a 3-aryl moiety--can be achieved in moderate yields by intramolecular radical arylation of pyridinium N-aminides using tris(trimethylsilyl)silane and azobisisobutyronitrile. Improved results were obtained on using Pd direct arylation in conjunction with microwave irradiation. A preliminary study into the fluorescent properties of the target compounds is also reported.