Two independent syntheses of the 1, 3-diazabiphenylene ring system have been developed. The first of these involves thermal extrusion of nitrogen from a condensed pyridazine precursor, and the second utilizes a diethynylpyrimidine in a cobalt-catalyzed co- oligomerizatioh reaction. The 1, 3-diazabiphenylenes undergo facile transformations to isoquinolines upon treatment with either acid or base. The intermediacy of 1, 3- ...
![4H-pyrimido[4,5-c]cinnolin-1-one Structure](https://image.chemsrc.com/caspic/044/87954-02-7.png)
![1-chloropyrimido[4,5-c]cinnoline Structure](https://image.chemsrc.com/caspic/006/87954-03-8.png)
![trimethyl(pyrimido[4,5-c]cinnolin-1-yloxy)silane Structure](https://image.chemsrc.com/caspic/344/87954-07-2.png)
![2-[4-methoxy-6-(2-trimethylsilylethynyl)pyrimidin-5-yl]ethynyl-trimethylsilane Structure](https://image.chemsrc.com/caspic/289/87954-13-0.png)
![1-methoxypyrimido[4,5-c]cinnoline Structure](https://image.chemsrc.com/caspic/306/87954-08-3.png)
