Synthesis of alkylidenecyclopentenones and dialkylidenecyclopentenones via the coupling of propargylic alcohol and 2-alkyne-1,4-diol derivatives with cyclopropylcarbene-chromium complexes

The coupling of propargylic alcohols and their derivatives with cyclopropylcarbene-chromium complexes has been investigated. The coupling reaction leads to alkylidenecyclopentenones or alkoxyalkyl-cyclopentenones, depending on the leaving group ability of the propargyl substituent. A mechanism involving formation of a cyclopentadienone, followed by reduction and -elimination is proposed. Coupling of cyclopropylcarbene complexes with 2-alkyne-1,4-diol derivatives leads to dialkylidenecyclopentenone derivatives via a double elimination process. © 2000 Elsevier Science Ltd