Pyrazine

Overview
Pyrazine is a heterocyclic aromatic organic compound.

Pyrazine is a symmetrical molecule with point group D2h. It is found in folic acid in the form of pterin. Derivatives like Phenazine are well known for their antitumor, antibiotic and diuretic activity. Pyrazine is less basic in nature than pyridine, pyridazine and pyrimidine. Tetramethylpyrazine is reported to scavenge superoxide anion and decrease nitric oxide production in human polymorphonuclear leukocytes. It is also found on the cigarette additives list.

Synthesis
Many methods exist for the organic synthesis of pyrazine and derivatives and some of them very old.

In the Staedel-Rugheimer pyrazine synthesis (1876) 2-chloroacetophenone is reacted with ammonia to the amino ketone, then condensed and then oxidized to a pyrazine A variation is the Gutknecht Pyrazine Synthesis (1879) also based on this selfcondensation but differing in the way the alpha-ketoamine is synthesised (the chlorine compound in the above method is a lachrymatory agent)


 * [[Image:Gutknecht Pyrazine Synthesis.svg|500px|Gutknecht Pyrazine Synthesis]]

The Gastaldi synthesis (1921) is another variation :


 * [[Image:GastaldiSynthesis.svg|400px|Gastaldi synthesis]]