Heterocyclic lithium amides as chiral ligands for an enantioselective hydroxyalkylation with n-BuLi.
Chiral heterocyclic structures based on 3-aminopyrrolidines (3APs), 3-aminotetrahydrothiophens (3ATTs), and 3-aminotetrahydrofurans (3ATFs) have been synthesized. The corresponding lithium amides have been evaluated as chiral ligands in the condensation of n-BuLi on o-tolualdehyde. The returned levels of induction were in the 46-80% ee range. The cheap and easily prepared 3ATFLi's turned out to be also the best ligands, giving access to the expected R or S alcohols in a same 80% level of induction at -78 degrees C in THF. In all cases, the sense of induction depends on the absolute configuration of C(8) on the 3-amino appendage. A general concept is proposed to rationalize the process of induction in the presence of organolithium species.
Laboratoire des Fonctions Azotées & Oxygénées Complexes de l'IRCOF, UMR CNRS 6014, Université de Rouen and INSA de Rouen, 76821 Mont St Aignan Cedex, France.
Nicolas
N
Duguet
Sylvain M
SM
Petit
Philippe
P
Marchand
Anne
A
Harrison-Marchand
Jacques
J
Maddaluno