Piperazine as leaving group in A3 adducts: Fast access to alkynyl indoles

The A3 coupling between N-ethylpiperazine and electron-rich aromatic aldehydes forms adducts that may be easily used as electrophiles towards electron-rich heterocycles such as indoles. The removal of the piperazine moiety is triggered by the addition of 1,2-dibromoethane. Overall, the reaction provides efficient access to alkynyl indoles and pyrroles.