Diphenyl hydrazine hydrochloride

Whilst anhydrous hydrazine is reported124) to give products of nucleophilic ring opening and cyclization (7 62/7 63) with diphenyl cyclopropenone, hydrazine hydrochloride yielded the azine 16112s ... 

Methy 1-1,5-diphenyl-1,2,4-triazole (3).4 A mixture of phenyl hydrazine hydrochloride 1 (14.5 g, 0.11 mol), N-acetybenzamide 2 (16.5 g, 0.1 mol) and NaOAc (10 g, 0.12 mol) in AcOH (30 mL) was refluxed for 10 h. The product was made alkaline vrth 10% NaOH solution and extracted with EtgO. Evaporation gave a pale yellow oil which slowly solidified, mp 80-81 C. Recrystalization from 90% EtOH and petroleum ether afforded 18.4 g of 3 (78%). 

Bicyclic lactams are uniquely suited as precursors for the synthesis of chiral substituted 4,5-dihydro-2H-pyridazinones. Thus, bicyclic lactams 112 with hydrazine dichloride in a dioxan/water mixture produced the desired 6-phenyl-4,5-dihydropyridazin-3-ones 113. However, reacting the bicyclic lactam with phenylhydrazine hydrochloride yields 2,6-diphenyl-4,5-dihydropyridazin-3-one 115 as a sole product (2004TL7799 Scheme 20). 

An ethereal soln. of diethylstyrylamine treated at 0° with benzoylformyl chloride in the presence of a slight excess of triethylamine under anhydrous conditions, after 1 hr. filtered to remove the resulting triethylamine hydrochloride, anhydrous hydrazine and some 2-propanol as solvent added 3,5-diphenyl-4(lH)-pyri-dazone. Y 60%. F. e. s. R. F. Abdulla, Tetrah. Let. 1976, 521. 

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