Three nitrile oxides (MeOCOC≡N→O, PhC≡N→O, and EtC≡N→O) were effectively generated in situ by dehydration of the corresponding primary nitro compounds (RCH2NO2) with PhSO2Cl or ClCOOEt in the presence of triethylamine. Various cycloadducts were prepared by the reaction of them with dipolarophiles. Some advantages of these methods are described in comparison with other known methods.

C-Ethoxycarbonylnitrilimines treated with monosubstituted olefins predominantly gave 5-substituted 3-ethoxycarbonyl-2-pyrazolines. From the analysis of the relative rate and regioselectivity of a variety of monosubstituted olefins for the cycloaddition, the nitrilimine is shown to have reactivity and regioselectivity similar to the throughly studied diphenylnitrilimine. The cycloaddition regioselectivity is discussed in terms of frontier orbital energies and coefficients.

A thermal decomposition of dimethyl nitromalonate to bis(carbomethoxy)furoxan was observed at about 170 °C. In the presence of dipolarophiles, an intermediate, methyl carbonocyanidate N-oxide MeOCOC≡N→O, could be trapped as cycloadducts in good yields by the 1,3-dipolar cycloaddition. Treatment of dimethyl nitromalonate in mesitylene at the refluxing temperature resulted in a formation of methyl 2-(hydroxyimino)-2-(2,4,6-trimethylphenyl)acetate.

The reaction of 2 molar equiv of several 2-(alkenyloxy)-l-naphthaldehydes (2) with hydrazine dihydrochloride (3) and subsequent treatment of the mixture with triethylamine lead to intramolecular [3+ + 2] criss-cross cycloadducts 5, 2:1 molar products of 2 and 3, in high yields. On the other hand, naphtho [l',2':5,6]pyrano-[4,3-c]pyrazoles 11 and 12, equimolar products of 2 and 3, were obtained by a similar series of reactions using a large excess of 3. Many pyrazolium chlorides (25), 2,2-dimethyl derivatives of 11, were prepared in high yields from the equimolar reaction of 2 with 1,1-dimethylhydrazine hydrochloride (24). -Phenyl, iV-decyl, and JV-dodecyl derivatives 29,31, and 32, respectively, of 25 were also prepared from the reaction using the corresponding AT-phenyl, iV-decyl, and TV-dodecyl derivatives of 24. Similarly, 1,2-dimethyl derivatives 41 of 11 were also prepared from an equimolar reaction of 2 with 1,2-dimethylhydrazine dihydrochloride. Intermolecular cycloadducts corresponding to these intramolecular ones were also obtained by the reactions of benzaldehyde with these hydrazine hydrochlorides Cycloaddition Routes to Azaanthraquinone Derivatives. 2. Use of Aza Dienes1

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