Benzal azine

The first example of a cycloaddition reaction of a multiple bond to a diene was reported in 1917 Surprisingly, it was found that benzal azine adds to 2 equivalents of several unsaturated systems, when offered in excess, to yield bicyclie compounds. This reaction was named criss-cross" cycloaddition [190], Exploitation of the preparative potential of criss-cross cycloaddition began only in the early 1970s, when hexafluoroacetone azine became available on a larger scale [191,192] The study of this reaction proved to be an impetus tor the development of azine chemistry [183, 193]... 

Azine of Tetrabromodintraminobenzoldehyde. See 3,3, 5,5 -Tetrabromo-4,4 -dinitramino-benzal azine... 

Oxidation of the hydrazone of 2-hydrazinopyrazole (226) with Pb(OAc)4 in CH2CI2 is a two-step reaction. The azine (227) was formed as an intermediate and this underwent ring closure to the 3H-pyrazolo[5,l-c][l,2,4]triazole (228) (79TL1567). A similar reaction applied to the benzal derivative of 2-hydrazinobenzothiazole (229) gave 3-phenyl-[l,2,4]triazolo[3,4-6]benzothiazole (230) together with a by-product (231) (72JCS(P1)1519). 

Plaza-Compounds. The criss-cross cycloaddition of JN-phenylmaleimide to benzal-dehyde azine, PhCH=NN CHPh, results in the pyrazolopyrazole-derivative (485) 432 hexafluoroacetone azine and ethyl acrylate or ethyl vinyl ether similarly yield the [l + 2] adducts (486 R = COOEt or OEt, respectively).433 — Compound (487) opens to the ylide (488) on heating in the presence of tetracyanoethylene the 4 + 2 ] cycloadduct (489) is formed, which fragments spontaneously to the beta-ine (490) and the diene (F,C),OCHCH-C(CN),. Thermolysis of the diazabicyclo-... 

On condensation with aldehydes hydrazine gives azines (ArCH = NN=CHAr) if the hydrazones prepared by condensation with benzal-dehyde are not crystalline, they can be condensed with a higher-molecular carbonyl compound, as, for example, o- or p-nitrobenzaldehyde, p-hydrox-ybenzaldehyde, etc. 

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