From Azines

A third method for the synthesis of cycl[3.2.2]azines, from iV-(aroylmethyl)pyridinium salts via indolizines, involves intramolecular (reductive) McMurry coupling of the latter. For example, 3,5-dibenzoylindolizines, obtained from 2-benzoyl-iV-phenacylpyridinium bromide as shown (Scheme 91), are cyclized using zinc and titanium(iv) chloride to give the 3,4-diphenylcyclazines 352 in high yield (>90%). The reaction cannot be applied, however, to... 

The initial step in Scheme 91 presumably involves deprotonation of the phenacyl substituent to give a pyridinium ylide. Such ylides may be generated as reactive (unstable) intermediates in the synthesis of cycl[3.2.2]azines from iV-(trimethylsilylmethyl)-2-pyridones (Scheme 92) in the presence of an excess of DMAD, the cyclazine is the major product <2003S1398>. 

The formation of cycl[3,2,2]azines from indolizines has its parallel in the saturated system with a reaction reported by Japanese workers.275 The indolizidinone ester 238 gives the tricyclic compound 239 on distillation with soda lime. This reaction is of potential importance in view of the number of alkaloids containing fused systems similar to 239. 

Aromatic aidaiines and ketazines.1 Polyphosphoric acid is an excellent catalyst and solvent for production of azines from aromatic aldehydes and ketones in the presence of various carbonyl reagents, for example, hydrazine, its salts, semicarbazide hydrochloride, toluenep-sulfonohydrazide, and acid hydrazides. The reaction is usually complete at 100° within 15 min. The reaction is not useful in the case of aliphatic carbonyl compounds. 

Examples of pyridazine synthesis from azines involve reaction between tetrafluoroformaldazine and perfluorosuccinyl fluoride in the presence of cesium fluoride to give a perfluoropyridazine, or via ketazine anions, as for acetophenone azine [Eq. (3)]. The azine from benzyl monohydrazone and ethyl acetoacetate or benzoylacetate is cyclized under basic conditions into the pyridazine 17. ... 

Shustov, G. V., Liu, M. T. H., Houk, K. N., Facile Formation of Azines from Reactions of Singlet Methylene and Dimethylcarbene with Precursor Diazirines Theoretical Explorations, Can. J. Chem. 1999, 77, 540 549. 

Reactions with sodium hydrazide Azines from 1,3-dienes s. 18, 382 NaNHNH ... 

Hydrogen sulfide l,3,4-Thiadiazol-2-one azines from 2,2 -azo-l,3,4-thiadiazoles... 

For a characteristic titration of 1,4-diphenylpiper-azine from which the N,N -diphenylethylenediamine has been removed, weigh 0.2 g of sample in a 150-ml beaker. Add 40 ml of acetic anhydride and titrate with O.IN perchloric acid. One equivalent of amine per mole is titrated in the tertiary amine determination and two equivalents of amine per mole are titrated in the characteristic titration for 1,4-diphenylpiperazine. 

The quaternization of pyrazine compounds has not been extensively studied, and, therefore, a detailed discussion of the effect of substituents is not possible. Recently Cheeseman has shown, from spectroscopic evidence, that 2-amino- and 2-diethylamino-p3rrazine (50, Y = NH2 and NEt ) quatemize at N-4, although protonation occurs at position-1. Other substituted p3U azines from which quaternary salts of structure 51 are formed include 2-chloro- and 2-... 

Hydrogen peroxide acetonitrile Azines from 0x0 compds. 

Di(acylhydrazones) s. 13, 456 Unsym. azines from bydrazones R.NNHg- R NN R ... 

Unsym. azines from hydrazones Oxidative coupling s. 14, 415 Phenoxazones by oxidative condensation... 

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