Aldol Reactions between L-Erythrulose Derivatives and Chiral α-Amino and α -Fluoro Aldehydes: Competition between Felkin–Anh and Cornforth Transition States
Both matched and mismatched diastereoselection have been observed in aldol reactions of a boron
enolate of a protected l-erythrulose derivative with several chiral α-fluoro and α-Amino aldehydes. Strict
adherence to the Felkin–Anh model for the respective transition structures does not account satisfactorily
for all the observed results, as previously observed in the case of α-oxygenatedaldehydes. In some cases,
only the Cornforth model provides a good explanation. The factors that influence this dichotomy are
discussed and a general mechanistic model is proposed for aldol reactions with a-heteroatom-substituted
aldehydes. Additional support for the model was obtained from density functional calculation
