Protiumdeuterium exchange of 17-oxosparteine: Homoenolization of a lactam

The H–D exchange of 17-oxosparteine (1b) has been studied under homoenolization conditions. We find that 1b undergoes H–D exchange at the bridgehead carbon C7 at 130 °C, but forcing conditions (240 °C) using the medium (CD 3 ) 3 COK/(CD 3 ) 3 COD are required to induce exchange at C11, C15, and other sites. C15-H a exchanges only marginally faster than C15-H c , indicating that the β-lactam carbanion is stabilized primarily by the dipolar …