Open PRAIRIE: Open Public Research Access Institutional Repository and Information Exchange
Abstract
A survey of the literature has been made on the syntheses of 2,5- and 2,6-dimethylpiperazines. Several new N-substituted dimethylpiperazines were subsequently prepared. These are: cis-2,6-dimethyl-4-mesyl-piperazine, cis-2,5-dimethyl-l,4-dimesylpiperazine, and trans-2,5-dimethyl-l,4-dimesylpiperazine (Jl). Attempted syntheses of trans-2,6-dimethylpiperazine (!±,) are also discussed. Room temperature nmr analysis of these and other previously known piperazine isomers supports the hypothesis that the more energetically equivalent equilibrating conformers are the more compact the AB portion of the ABX pattern of the piperazine ring protons. This technique provides a convenient method for suggesting the configuration and conformation at room temperature of the seventeen isomers and derivatives that were studied. Piperazine ring proton assignments are based on coupling constants and chemical shifts. Steric factors influencing room temperature nmr analysis are also discussed
