2177-78-8Relevant articles and documents
REGIOSPECIFIC ADDITION OF ORGANOCOPPER REAGENTS TO α,β-UNSATURATED ESTERS
Behforouz, Mohammad,Curran, Timothy T.,Bolan, Joseph L.
, p. 3107 - 3110 (1986)
Mixed cuprates ArSCu(RMgX)n add rapidly to crotonates and cinnamates to give high yields of Michael adducts.Cuprates of methyl, ethyl, isopropyl, t-butyl, phenyl and vinyl were used.Crotonates give much higher yields of adducts with cuprates using 2-methoxythiophenoxide as a ligand than with those using thiophenoxide.
Primary alkanols: oxidative homocondensation in water and cross-condensation in methanol
Nikishin,Sokova,Terent′ev,Kapustina
, p. 2845 - 2850 (2016/09/28)
Water was used as a reaction medium and a reagent in oxidation of primary alkanols to dimeric esters and alkanoic acids using either molecular bromine or a hydrogen peroxide—hydrobromic acid mixture as the oxidants. The similar reaction in methanol produced methyl alkanoates.
Steric effects and mechanism in the formation of hemi-acetals from aliphatic aldehydes
Daw, Graham,Regan, Andrew C.,Watt, C. Ian F.,Wood, Evan
, p. 1048 - 1057 (2014/01/06)
Some physical properties (pKa, log POW, boiling points) of hexanoic acid 1 (X = COOH) and its seven isomers 2, 3, 4, 5, 6, 7, 8 (X = COOH) are reported. Hexanal 1 (X = CHO) and its seven isomeric aldehydes 2, 3, 4, 5, 6, 7, 8 (X = CHO) are shown to equilibrate, in methanol solution, with their hemi-acetals. Logarithms of equilibrium constants correlate with values of Es for the isomeric C5H11 substituents, and with logs of relative rates for saponification of the corresponding methyl esters with ρ = 0.52, reflecting the reduced steric demand of hydrogen compared to oxygen in the quaternization of ester and aldehydic carbonyl groups. Rates of equilibration have also been measured in buffered methanol. For hexanal, with a 2:1 Et3N:AcOH buffer, the buffer-independent contribution is dominated by the methoxide catalysed pathway. Rates in this medium have been determined for isomers 1, 2, 3, 4, 5, 6, 7, 8 (X = CHO), and their logarithms do not correlate with logarithms of equilibrium constants for hemi-acetal formation or with substituent steric parameters derived from ester formation or saponification, indicating that the steric changes associated with full quaternization of the carbonyl group are not mirrored in the transition structures for hemi-acetal formation. It is suggested that transition states for hemi-acetal formation are relatively early so that steric interactions are effectively those between the nucleophile and ground state conformations of the aldehydes. A comparison of the entropies of hemi-acetal formation with entropies of activation has provided a basis for a suggested transition structure. Comparisons with acid chloride hydrolyses are made. Copyright 2013 John Wiley & Sons, Ltd. Logarithms of equilibrium constants for formation hemi-acetals of hexanal and its seven isomeric aldehydes correlate well with values of Es for the isomeric C5H11 substituents, and with logs of relative rates for saponification of the corresponding methyl esters. Logarithms of rate constants for hemi-acetal formation do not, indicating that the steric changes associated with full quaternization of the carbonyl group are not mirrored in the transition structures for hemi-acetal formation. The reasons for this are discussed. Copyright
Highly efficient copper(I) iodide-tolyl-BINAP-catalyzed asymmetric conjugate addition of methylmagnesium bromide to α,β-unsaturated esters
Wang, Shun-Yi,Lum, Tze-Keong,Ji, Shun-Jun,Loh, Teck-Peng
supporting information; experimental part, p. 673 - 677 (2009/04/10)
A highly efficient asymmetric conjugate addition of methylmagnesium bromide (MeMgBr) to α,β-unsaturated esters catalyzed by copper(I) iodide-tolyl-BNIP (CuI-Tol-BINAP) is described.
Copper-catalyzed enantioselective conjugate addition of Grignard reagents to α,β-unsaturated esters
Lopez, Fernando,Harutyunyan, Syuzanna R.,Meetsma, Auke,Minnaard, Adriaan J.,Feringa, Ben L.
, p. 2752 - 2756 (2007/10/03)
(Chemical Equation Presented) Stable dinuclear Cu complexes have been used to catalyze the conjugate addition of inexpensive and readily available Grignard reagents to acyclic α,β-unsaturated esters. The method provides the correspending β-substituted optically active esters in high yields and with excellent enantioselectivities (see scheme). R3 = cyclohexyl, R 4 = Ph or R3 = Ph, R4 = cyclohexyl.
Complete structures of the sphingosine analog mycotoxins fumonisin B1 and AAL toxin T(A): Absolute configuration of the side chains
Shier,Abbas,Badria
, p. 1571 - 1574 (2007/10/02)
Fumonisin B1 and AAL toxin T(A) are sphingosine-analog mycotoxins characterized by propane-1,2,3-tricarboxylic acid side chains esterified to alkylamine backbones. The absolute configuration of all stereogenic centers in the backbones is known. Using chiral gas chromatography methodology we have determined the absolute configuration at C-3' in the side chains to the S, thereby completing structure determination of both toxins.
THE SYTHESIS OF γ-FLUOROISOLEUCINE
Butina, D.,Hudlicky, M.
, p. 301 - 324 (2007/10/02)
Condensation of 3-fluoro-2-butanone (2) with alkyl diethylphosphonoacetates (4a-d) gave alkyl 4-fluoro-3-methyl-2-pentenoates (5a-d).Addition of bromine yielded alkyl-2,3-dibromo-4-fluoro-3-methylpentanoates (6a,b) which were dehydrobrominated to alkyl 2-bromo-4-fluoro-3-methyl-2-pentenoates (7a,b).Since these compounds could not be hydrogenated to the desired alkyl 2-bromo-4-fluoro-3-methylpentanoates (8a,b), another route was taken.The esters 5a-d were hydrogenated to alkyl 4-fluoro-3-methylpentanoates (11a-c) which were converted to their carbanions.Treatment with bromine gave esters 8a-c, and iodine gave alkyl 4-fluoro-2-iodo-3-methylpentanoates (12a,b).Esters 8a-c and 12a,b were converted to alkyl 2-azido-4-fluoro-3-methylpentanoates (13a-c) whose hydrogenation gave alkyl 2-amino-4-fluoro-3-methylpentanoates (14a-c).Hydrolysis afforded γ-fluoroisoleucine (1).
