The conjugate addition of enantiomerically pure lithium amides as homochiral ammonia equivalents: scope, limitations and synthetic applications

Lithium Diisopropylamide-Mediated Reactions of Imines, Unsaturated Esters, Epoxides, and Aryl Carbamates: Influence of Hexamethylphosphoramide and Ethereal Cosolvents on Reaction Mechanisms

“…Dehydrobrominations of alkyl bromides proceed by mono-, di-and trisolvated monomers (14)(15)(16)(17)(18)(19) as well as triple ions (20). 5 The highly variable solvation numbers are unusual when compared with LDA-mediated reactions in standard ethereal solvents.…”

A Convenient Asymmetric Synthesis of a β-amino Ester with Additional Functionalization as a Precursor for Peptide Nucleic Acid (PNA) Monomers

“…Whereas (E)-α,β-unsaturated esters are very susceptible to conjugate addition, their (Z)-counterparts are highly susceptible to γ-deprotonation [8,9]. This suggested a strategy towards the monoadduct 9 from di-3-pentyl (E,Z)-deca-2,8-diendioate 7.…”

Diastereoselective conjugate addition of (R)-4-phenyl-2-oxazolidinone to dialkyl alkylidenemalonates

“…THF (8 mL) was added and the white suspension obtained was stirred at 0 °C for 30 min and then cooled to -78 °C. A solution of the dialkyl alkylidenemalonate 2 (1.0 mmol) in THF (2 mL) cooled at 0 °C was added slowly and then the reaction mixture was stirred at -78 °C for 1-6 h. A saturated aqueous NH 4 Cl solution (5 mL) was added. The aqueous phase was extracted with diethyl ether (3 × 10 mL).…”

“…[1][2][3] Among these, approaches involving an aza-Michael reaction have often been used. In this process, the asymmetric induction may come either from a chiral nitrogen nucleophile, [4][5][6] or from a chiral conjugate electrophile, [7][8][9][10][11] or from a chiral ligand, employed either stoichiometrically 12,13 or catalytically. The major diastereoisomer of adduct 3h, obtained from (R)-4-phenyl-2-oxazolidinone and dimethyl benzylidenemalonate was isolated by crystallization and single crystal X-ray diffraction studies established the configuration of the newly created stereogenic center as S (Figure 1).…”