Imidazol 1,2-6 pyridazine 1-oxides

Photochemical hydroxyalkylation has been carried out with pyri-dines, quinolines, isoquinolines,acridine, pyridazines, pyrimidines, ethoxyquinolinium salts,and imidazoles. It also occurs with iV-oxides the mechanism of Scheme 13 has been suggested for pyridazine iV -oxide. ... 

Some of the ring expansion reactions discussed in Section 2.03.3.3.1 can be extended to five-membered heterocycles containing two or more heteroatoms. Reaction of imidazoles and pyrazoles with dichlorocarbene, for example, gives chloropyrimidines together with small amounts of chloro-pyrazines or -pyridazines, and oxidative ring expansion of 1-aminopyrazole with nickel peroxide gives 1,2,3-triazine (this, in fact, constitutes the only known synthesis of the unsubstituted triazine). There are, however, a number of interesting and useful transformations which are unique to five-membered polyheteroatom systems. 

The following abbreviation ) are used in this index (see p. 663) azep, azepine im, imidazole Nox, N-oxide O2. dioxide ox, oxazine oxdazol, oxadiazole oxep, oxepine p. pyridine paz, pyrazine pdaz. pyridazine pm, pyrimidine prr, pyrrole pzol, pyrazole tetrazep, teirazepine ihzn, thiazine thzol, ihiazole triazep, triazepine trzn, triazine. 

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