Conjugate addition of lithium isopropyl dithioisobutyrate to 4-acetoxycyclopent-2-enone. Assignment of stereochemistry in flexible 5-membered rings

Abstract

Lithium isopropyl dithioisobutyrate is alkylated on the S atom by 4-bromocylopent-2-enone but on the C atom by cyclopent-2-enone and 4-acetoxycyclopent-2-enone via conjugate addition; the stereochemistry of the 3,4-disubstituted cyclopenanone from the latter reaction is established by the determination of the long-range coupling constants, ⁴J_HH.