Asymmetric metal-catalysed epoxidation of electron-deficient olefins
摘要:
The SYN diastereospecific epoxidation of acyclic beta-hydroxyketones (beta-hydroxyacrylates) and cyclic beta-hydroxyketones using titanium and vanadium catalysts is reported. Some initial results on the asymmetric epoxidation of these systems using the Sharpless titanium-tartrate catalyst are also described.
An efficient and simple Morita–Baylis–Hillman reaction based on the N-methylpyrrolidine–Ba(OH)2 catalytic system
作者:Krassimira P. Guerra、Carlos A.M. Afonso
DOI:10.1016/j.tet.2011.02.020
日期:2011.4
By using of precise catalytic amount of N-methylpyrrolidine (5 mol %) and Ba(OH)2 (1.5 mol %) in H2O/CH3OH 5/1 or CH3OH/CH2Cl2 3/1 solvent mixtures at T=0 °C a Morita–Baylis–Hillman derivatives could be obtained in good to excellent yield from 2-cyclopenten-1-one, 2-cyclohexen-1-one and formaldehyde and diverse aryl aldehydes after suitable reaction time.
Vinyl Anion Equivalents. Part IV. Efficient Synthesis of 2-(1-Hydroxyalkyl)-2-cyclopenten-1-ones
作者:Shinya Kusuda、Yoshio Ueno、Takeshi Toru
DOI:10.1246/bcsj.66.2720
日期:1993.9
Aldol reactions of lithium enolates resulted from conjugate additions of tributylstannyllithium to 2-(phenylseleno)-2-cyclopenten-1-one provides 2-(1-hydroxyalkyl)-2-cyclopenten-1-ones in high yields. Significantly good 1,4-asymmetric induction took place in analogous aldol reactions starting with chiral 4-[(t-butyldimethylsilyl)oxy]-2-(phenylseleno)-2-cyclopenten-1-one.
Intramolecular photochemical reactions of 2-acyl-4-oxa-1,5-hexadienes
作者:Albert R. Matlin、Thomas C. Leckta、David J. McGarvey、Peter W. Jacob、Harold A. Picken
DOI:10.1016/s0040-4039(00)95596-5
日期:——
Photolysis of alkyl-substituted 2-(2-oxa-3-butenyl)cyclopent-2-enones gives rise to derivatives of bicyclo[2.1.1]hexanes (“rule of five” product), and α-methylenecyclopentanones(photo-Claisen rearrangement). Methyl substitution remote from the bond forming centers produces a regioselective reaction yielding only the “rule of five” product.
For the first time the rhodium-catalyzed 1,4-addition of organoboranes to hindered Baylis−Hillman adducts, trisubstitutedalkenes, affording highly functionalized alkenes, via addition of the organoboranes and hydroxyelimination, is reported. Moreover, preliminary results have shown that, thanks to the use of a monosubstituted chiral diene ligand, enantio-enriched products were easily accessible, while
Metal catalyst-free N-allylation/alkylation of imidazole and benzimidazole with Morita–Baylis–Hillman (MBH) alcohols and acetates
作者:Olfa Mhasni、Jalloul Bouajila、Farhat Rezgui
DOI:10.3762/bjoc.19.93
日期:——
substitution of cyclic MBH alcohols and acetates with imidazole or benzimidazole, in toluene at reflux with an azeotropic distillation, was successfully carried out with no catalysts or additives, affording the corresponding N-substituted imidazole derivatives in good yields. On the other hand, in refluxing toluene or methanol, the aza-Michael addition of imidazole onto acyclic MBH alcohols was performed using