SYNTHESIS OF N-(TRIISOPROPYLSILYL)ALDIMINES AND N-(TERT-BUTYLDIMETHYLSILYL)ALDIMINES AND THEIR APPLICATION IN THE SYNTHESIS OF BETA-LACTAMS

A new and efficient synthesis of N-(TIPS)imines and N-(TBDMS)imines st arting from enolizable and non-enolizable aldehydes is described. We t ested the reactivity of these imines in the preparation of beta-lactam s. N-(TBDMS)imines effectively give N-(TBDMS)azetidinones with a trans stereochemistry of the ring substituents, complementing N-(TMS)imines which instead afford cis beta-lactams. In contrast, N-(TIPS)imines re act with ester enolates in few cases because of the extremely low rate of the ring-closure step, so that a decomposition of enolates occurre d.