Synthesis of 2-Cyclohexenone-2-carboxylate and 4-Chloro-2-cyclohexenone-2-carboxylate Derivatives by Cyclization of Alkyne-Tethered 1,3-Ketoesters

摘要

A method for the TfOH-promoted (Tf=trifluoromethanesulfonyl) cyclization of alkyne-tethered 1,3-ketoesters to afford 2-cyclohexenone-2-carboxylate derivatives has been developed. The procedure requires no transition-metal reagent or catalyst and is practical to conduct under mild conditions. 2-Cyclohexenone-2-carboxylate derivatives were obtained in moderate to good yields without any evidence of decarboxylation. In addition, the approach can be easily adapted as a one-pot sequential cyclization/chlorination protocol that selectively provides access to 4-chloro-2-cyclohexenone-2-carboxylate derivatives in moderate to good yields.