Reaktionen Von Acetylencarbonsäureestern Mit Piperazinderivaten

Abstract

Hg(II)-EDTA-dehydrogenation of benzylpiperazine (5) in 50% ethanol with addition of diethyl acetylenedicarboxylate (2) to a minor extent gives rise to (piperazine-1,4-diyl)-bis(maleate) (9), which is inert to Hg(II)-EDTA and results in quantitative yield when Hg(II)-EDTA is omitted. 4- Benzylpiperazin-1-yl)-monomaleate (8) reacts with 2 in various solvents by addition of water with dealkylation and formation of 9. CH-acidic compounds may also be used as proton donors. Analogous reactions, although with minor yields, occur with the propiolates 11 and 12. 1-Substituted piperazines with benzyl, methine or allylic groups (5 -5c, 27d - g, and 27h) react readily with acetylenedicarboxylic acid esters to give compounds of type 9, whereas benzhydryl, aromatic and most of the unbranched aliphatic substituents are not replaced. The reactivity of 1,4-disubstituted piperazines corresponds largely to the behaviour of the substituents in the monosubstituted derivatives