Short synthesis of enantiopure trans-3-arylpiperazine-2-carboxylic acid derivatives via diaza-Cope rearrangement.

An efficient synthetic method was developed for the construction of enantiomerically pure trans-3-arylpiperazine-2-carboxylic acid derivatives using diaza-Cope rearrangement (DCR) as a key step starting from (R,R)/(S,S)-1,2-bis(2-hydroxyphenyl)-1,2-diaminoethane (HPEN). A complete transfer of stereochemical integrity was observed for the transformation. Piperazine ring formation from the chiral 1,2-ethylenediamine derivatives using diphenylvinylsulfonium triflate followed by oxidation using ruthenium(III) chloride monohydrate in the presence of sodium periodate provided the desired enantiopure trans-3-arylpiperazine-2-carboxylic acid derivatives.