Baylis-Hillman chemistry: a convenient stereoselective synthesis of (Z,Z)-and (E,E)-1,4-diallylpiperazines

Treatment of piperazine with 3-acetoxy-2-methylenealkanenitriles provides e xclusively (1,4)-bis[(2,Z)-2-cyanoalk-2-en-1-yl]piperazines. A similar reac tion of methyl 3-acetoxy-3-aryl-2-methylenepropanoates with piperazine prod uces (1,4)-bis[(2E)-3-aryl-2-methoxycarbonyl prop-2-en-1-yl]piperazines as the major products.