Cyanogen di-N-oxide reacts, through a double 1.3-dipolar addition, with o-phenylenediamines, o-aminophenols. and 1.2-dithiols to give good yields of the corresponding heterocyclic dioximes. The spectral data of the compounds are discussed in relation to their structure.ALTHOUGH cyanogen di-N-oxide (I) was first prepared in 1911, its properties and the reactions have been studied only recently, by Grundmann and his co-workers.2 Besides having a tendency to give polymers, it reacts, like other nitrile oxide^,^ with amines or 1,Z-diamines to form substituted amidoximes, e.g. with o-phenylenediamine and ethylenediamine it gives 2,3-bishydroxyimino-l,2,3,4-tetrahydroquinoxaline (11) and 2,3-bishydroxyiminopiperazine respectively.2 The reaction was found to be a general one and treatment of o-phenylenediamines, o-aminophenols, and o-phenylenedithiols with cyanogen di-N-oxide gave quinoxalines, 2,3-bishydroxyimino-2,3-dihydro-4H-benzoxazines (111) , and 2,3-bishydroxyimino-l,4-benzodithians (IV) respectively. The formation of polymers was avoided by keeping the reaction mixture cool and employing dilute solutions of the reactants. The yields, based on the dichloroglyoxime used, were in the range 40-50%.The order of relative reactivity for the groups on reaction with cyanogen di-N-oxide was NH, > SH > OH. The low W. Steinkopf and €3.

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1‐Benzyl‐5,6‐dihydro‐1H,2,3‐triazolo[4,5‐d]pyridazine‐4,7‐dione (1) by oxidation with lead tetraacetate afforded the corresponding triazolopyridazine‐4,7‐dione 2 as the intermediate, which was trapped with several dienes giving the hetero‐Diels‐Alder adducts 3 in good yields. The structure of the cycloadduct 3a was determined by X‐ray analysis.

The synthesis of the title compounds 3 upon cyclodehydration with thionyl chloride of the corresponding bis‐aroylhydrazides 2 is described and their spectral properties are examined.