Intramolecular dehydrochlorination of [2-(N’,N’-dialkylhydrazino)ethyl]phosphonium salts. Chemoselective alkaline hydrolysis of triphenylphosphonioalkylhydrazinium salts

The reactions of N,N-dimethylhydrazine and N-aminopiperidine with potential triphenylvinyl-and-propenylphosphonium bromides were used to obtain adducts by the α,β-double bonds of the latter. The resulting 2-(N’,N’-dimethylhydrazino)ethyl]phosphonium salts just on moderate heating in alcohol undergo dehydration leading to the corresponding hydrazone or α,β-unsaturated hydrazine derivatives. Contrary to that, 2-(N’,N’dimethylhydrazino)-2-methylethyl]triphenylphosphonium bromide under the same conditions does not undergo dehydration. The reaction of (3-bromopropyl)-and (4-bromobutyl)triphenylphosphonium bromides with N,N-dimethylhydrazine gives phosphoniohydrazinium salts with a tri-or tetramethylene common radical. When treated with equimolar amount of ethanolic sodium ethylate, the latter products undergo alkaline reduction of one of the phenyl groups to give the corresponding diphenylphosphinoylalkylhydrazinium salts in high yields.