Pyrazinium chlorochromate

Acyloxy- and acylthiopyrazines are convenient acylation reagents for benzylamine, aniline, pyrrolidine, and related compounds (see Section 6.03.8.3). The acylthio compounds are also useful for acylation of alcohols and phenols. Pyrazinyl alkyl sulfoxides (see Section 6.03.8.4) give aldehydes and ketones by treatment with TFAA <91H(32)937>. The pyrazinium chlorochromate salt (181) is formed by addition of chromium(VI) oxide to a solution of pyrazine in hydrochloric acid, and it has proved to be more effective for the oxidation of aliphatic and allyl alcohols to the aldehydes than pcc <83H(20)2029>. 

BTPPD), isoquinolinium bromochromate (IQBC), morpholinium chlorochromate (MCC), nicotinium dichromate (NDC), pyrazinium chlorochromate (PzCC), pyri-dinium bromochromate (PBC), pyridinium chlorochromate (PCC), pyridinium fluoro-chromate (PFC), quinolinium chlorochromate (QCC), quinolinium dichromate (QDC), quinolinium fluorochromate (QFC), tetraethylammonium chlorochromate (TEACC), tetramethylammonium fluorochromate (TMAFC), and some metal salts have been reported and these are described below. 

Other ammonium chlorochromates, occasionally used in the oxidation of alcohols, include pyrazinium-A-oxide (PzOCC),378 naphtyridinium (NapCC),394 pyrazinium (PzCC),394 tripyridinium hydrochloride (TPCC),378a triethylammonium,378b imidazolium and l-methylimidazolium,194e and ben-zyltrimethylammonium (BTMACC)387j chlorochromates. 

Preparation of pyrazinium -oxide chlorochromate gives a reagent which is as reactive as PCC, but much less stable.Again there is no apparent selectivity for a particular type of substrate. 

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