Synthesis of 4-Hydroxy-2-cyclopentenone Derivatives by [3 + 2] Annulation of β-Heteroatom-Substituted Acryloylsilanes and Lithium Enolate of Methyl Ketones

The [3 + 2] annulation using β-[2-(pyridyl)thio] and β,β-dichloro derivatives of acryloylsilane and the lithium enolate of methyl ketones successfully proceeded to afford 4-alkyl-4-hydroxy-3-(2-pyridylthio)cyclopentanone and 4-alkyl-3-chloro-4-hydroxy-2-cyclopentenone, respectively.