Piperazine, proton transfer

The extent of proton transfer was also studied in complexes between genistein and piperazine. This was done by comparing solid and solution state C spectra . ... 

A mechanism for the piperazine-catalyzed formation of 4//-chromenes is complex cascade of reactions, starting with piperazine acting as a base which activates malononitrile, promoting Knoevenagel condensation, and also formation of an enamine, followed by Michael condensation, proton transfer, intermolecular cycliza-tion via a nucleophilic addition of the enolate oxygen to the nitrile group (hetero-Thorpe-Ziegler), and finally hydrolysis and tautomerization. 

More complicated aminolysis reaction has been studied theoretically for cyclo-hexadiene monoepoxide interaction with N-(3-chlorophenyl)piperazine [54], Both pathways corresponding to front- and rear-side attacks have been found. The first pathway is one-step reaction where breaking of C-O bond, forming of C-N bond and proton transfer between N and O atoms occur simultaneously (Fig. 10.11). In contrast, at the first step of near-side attack zwitterionic intermediate is formed... 

Using diamines such as N,N -dimethylethylenediamine or piperazine leads to the formation of heterocycle-fused fullerene derivatives 23 and 24 (Figure 28.4). > Again, the reaction proceeds via single elctron transfer to give the C -D radical ion pair followed by successive intermolecular proton transfer, which completes the addition reaction with [60]fuUerene. 

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