Asymmetric Cyclization of Achiral Olefinic Organolithiums Controlled by a Stereogenic Lithium:  Intramolecular Carbolithiation in the Presence of (−)-Sparteine

Beyond Thermodynamic Acidity: A Perspective on the Complex‐Induced Proximity Effect (CIPE) in Deprotonation Reactions

“…[53] A high intermolecular protium/deuterium isotope effect for the reaction of 42 and [2,2,5,5-D 4 ]42 indicates that the reaction proceeds with rate-determining proton transfer. The structure of the complex 43, which acts as the base, was determined by 1 H, 13 C, and 6 Li NMR spectroscopic studies. [54] The rate is independent of the concentration of organolithium reagent, as a zeroorder dependence on organolithium concentration was observed under pseudo-first-order conditions in 42.…”

Inter- and intramolecular enantioselective carbolithiation reactions

“…Hence, the enantioselective intramolecular carbolithiation of N -allyl-2-bromoanilines by using tert -butyllithium in the presence of (−)-sparteine ( L1 ) for the synthesis of 3-substituted indolines, was reported simultaneously by Bailey [45] and Groth [46]. Thus, ( R )-(−)-1-allyl-3-methylindoline ( 38a ) was obtained in high yield and ee by reaction of N , N -diallyl-2-bromoaniline ( 37a ) with t- BuLi in n -pentane/diethyl ether in the presence of (−)-sparteine ( L1 ) (Scheme 13).…”

“…While solvent systems composed of hydrocarbon/diethyl ether are effective, the use of THF resulted in almost complete loss of enantioselectivity. The cyclization of amine 37b under identical conditions was less enantioselective than the analogous diallyl substrate 37a (70% versus 86%) [45]. On the other hand, N -allyl- N -benzyl-2-bromoaniline ( 39 ) also undergoes enantioselective intramolecular carbolithiation with t -BuLi/(−)-sparteine ( L1 ) in toluene as solvent (Scheme 13) [46].…”

Investigation of bispidines as the stoichiometric ligand in the two-ligand catalytic asymmetric deprotonation of N-boc pyrrolidine

“…s-BuLi or n-BuLi) and (-)-sparteine have been used for the asymmetric synthesis of a diverse range of compounds including amines, 6 alcohols, 7 phosphines, 8 ferrocenes 9 and paracyclophanes. 10 An example from Bailey and Mealy 11,12 is representative of the synthetic potential afforded by organolithium/(-)-sparteine reagents. Treatment of di-allylated bromoaniline 1 with t-BuLi/(-)-sparteine 3 followed by incubation at -40 °C and quenching with MeOH delivered chiral indoline (R)-2 in 69% yield and 93:7 er (Scheme 1).…”