Benzaldehyde phenylhydrazones, addition

Benzaldehyde phenylhydrazone with DM AD gave 8% of dimethyl 1,3-diphenylpyrazole-4,5-dicarboxylate (136) together with 35% of trimethyl pyrazoletricarboxylate (138), which the authors suggest is obtained from the primary adduct 137 by Michael addition of a second mole of DMAD followed by cleavage, as shown.129... 

Benzaldehyde shows most of the reactions which are characteristic of aliphatic aldehydes. It reduces an ammonaical solution of silver nitrate, forms addition-products with acid sodium sulphite and with hydrocyanic acid, is converted by nascent hydrogen into an alcohol, and yields an oxime and a phenylhydrazone. 

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