Structure and reactivity of lithium diisopropylamide (LDA) in hydrocarbon solutions. Formation of unsolvated ketone, ester, and carboxamide enolates
摘要:
Enolization of ketones, tert-butyl esters, and carboxamides by solvent-free lithium diisopropylamide (LDA) in hexane or toluene are described. Enolates are isolated as spectroscopically pure, white (often crystalline) solids. Solubilities of the enolates in hexane range from highly soluble to completely insoluble. Enolizations of aldehydes, methyl esters, and acetone afford complex mixtures. Analysis of [Li-6]LDA and [Li-6, N-15]LDA in hexane by Li-6 and N-15 NMR spectroscopy show evidence of an equilibrium mixture of at least three cyclic oligomers.
Surprises in enolate binding at high valent molybdenum
作者:Paul A. Cameron、Vernon C. Gibson、David J. Williams、Andrew J. P. White
DOI:10.1039/a800116b
日期:——
Treatment of [Mo(NAr)2Cl2(DME)] (Ar = 2,6-diisopropylphenyl; DME = 1,2-dimethoxyethane) with LiOC(OBut)CMe2 at low temperature affords the unexpected carbon-bound molybdenum(VI) enolate complex [Mo(NAr)2Clη2-C(Me2)CO2But}] 1; the novel α-aminoenolate derivative [Mo(NAr)2Clη2-CH(NMe2)CO2Et}] 2 is obtained under analogous conditions using LiNPri2/Me2NCH2CO2Et; the structures of 1 and 2 confirm the carbophilic nature of the [Mo(NAr)2] core.
Regiocontrolled 1,2-, 1,4-, and 1,6-additions of organometallics to unsaturated thioamides
作者:Y. Tamaru、T. Harada、S. Nishi、Z. Yoshida
DOI:10.1016/s0040-4039(00)87348-7
日期:——
1,4-Addition of allyllithiums to α,β-unsaturated thioamides and 1,4-(kinetic) and 1,6-(thermodynamic)regiocontrolled additions of lithium enolates to thiosorbamide are reported.
A factor affecting enantioselective reaction of a ternary complex of lithium ester enolate with imine
作者:Takeshi Kambara、Mostafa Ahmed Hussein、Hiroki Fujieda、Akira Iida、Kiyoshi Tomioka
DOI:10.1016/s0040-4039(98)02053-x
日期:1998.12
Systematic investigation of the varying size of the alkoxy moiety of the lithiumesterenolates in the chiral ligand mediated reaction with imines led to the improvement of the enantioselectivity of β-lactam products in up to 93%. The asymmetric induction step was indicated to be the addition step, not the cyclization step.