Hydrazonoyl chlorides cycloaddition

Diphenylnitrilimine (DNPI) can be subjected to 1,3-dipolar cycloaddition with activated double bonds as dipolarophiles (Eq. 54). It can be generated in situ by reaction of hydrazonoyl chloride with a base. 

The cycloaddition of nitrilimines toward furo[3,4-c]thieno[2,3-r7]-pyrazoles has been investigated as a function of the electron-withdrawing or electron-donating character of the substituents attached to the aromatic rings <2000H(53)917>. For instance, nitrilimine 459, obtained in situ from hydrazonoyl chloride 458, by base treatment with silver carbonate in dioxane, when reacted with 460, gives a mixture of compounds 461 and 63 (Scheme 53) <2000H(53)917>. 

A study of the 1,3-dipolar cycloaddition of pyrazines, pyrimidines and l//-pyrimidinthiones with nitrilimines (80), generated in situ by dehydrohalogenation of the corresponding hydrazonoyl chlorides (79), was carried out. Reaction of pyrimidine-2( l//)-thiones (81) and -4(l//)-thiones with nitrilimines in benzene at reflux gave spiro[pyrimidine-2(l//), 2 (3 f/)-[ 1,3,4]thiadiazoles... 

Upon base treatment with silver carbonate, isoxazolyl-substituted hydrazonoyl chlorides underwent a sequential intra-intermolecular nitrilimine 1,3-dipolar cycloaddition, leading to tetracyclic pyrazolidines (Equation 6) <2000H(53)831>. 

Solvent-free 1,3-dipolar cycloaddition of diphenylnitrUimine 13, generated in situ from hydrazonoyl chloride, to olefins 184 was efficiently catalyzed by a combination of porous calcium hydroxyapatite, serving both as base and as solid support, and microwaves. A key feature of this catalyst/solvent-free system is the recy-... 

Cycloaddition reactions of l,3,4-oxadiazin-6-ones 97 (R = Ph, R = Ar), via their 2,3-diaza-l,3-diene functionality, are observed by treatment with dipolarophiles. Thus, 2,5-diaryl-l,3,4-oxadiazines 97 react with diaryl nitrilimines 115, which are liberated in situ from the corresponding hydrazonoyl chlorides 114 and triethylamine, to give 1//-1,2,4-triazole A -imines 118 and open-chain products 119 <1996JHG591>. It is reasonable to conclude that intermediates 116 are formed initially from cycloaddition across the adjacent carbonyl-carbon nitrogen double bond and that subsequent CO abstraction gives 177-1,2,4-triazole A -imine derivatives 118. The open-chain adducts 119 are formed from intermediates 117, which result from the reaction of 115 at the carbonyl double bond of the oxadiazinones 97 (Scheme 15). 

Molteni found that nitrilimine 94, generated in situ from hydrazonoyl chloride 93, reacted with electron-poor dipolarophiles (i.e. ethylacrylate in Scheme 5.24) to give pyrazo-lines in water under basic conditions and in the presence of tetrahexylammonium chloride. The presence of surfactant reduced the formation of the by-product 1,2,4,5-tetrazine derivative coming from the dimerization of 94. On the basis of a computational study, the authors conclude that the water has a rather small effect on the cycloaddition with respect to that played by the surfactant. 

The 1,3-dipolar cycloaddition of hydrazonoyl chlorides (74) with the sodium salt of benzoylacetone produced a mixture of regioisomeric 27f-pyrazoles, viz. 4-acetyl-5-phenyl-3-substituted-l-arylpyrazoles (75) and 4-benzoyl-5-methyl-3-substituted-l-arylpyrazoles (76) (Scheme 27). ... 

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