An enantioselectiveBiginellireaction that proceeds by a dual-activation route has been developed by using a combined catalyst of a readily available trans-4-hydroxyproline-derived secondary amine and a Bronsted acid. Aromatic, heteroaromatic, and fused-ring aldehydes were found to be suitable substrates for this multicomponent reaction. The corresponding dihydropyrimidines were obtained in moderate-to-good
Enantioswitchable Catalysts for the Asymmetric Transfer Hydrogenation of Aryl Alkyl Ketones
作者:Alexey B. Zaitsev、Hans Adolfsson
DOI:10.1021/ol062227q
日期:2006.10.1
ruthenium-catalyzed reduction of ketones under hydrogentransfer conditions. In addition, in most cases, a switch of the product's absolute configuration was observed on going from amides to the corresponding thioamides. Under optimized conditions, we obtained the secondary alcohol products in high yield and enantioselectivity (up to 97% ee) using only 0.25 mol % catalyst loading. [structure: see text]
Direct amide formation using radiofrequency heating
作者:Thomas K. Houlding、Kirill Tchabanenko、Md. Taifur Rahman、Evgeny V. Rebrov
DOI:10.1039/c2ob26930a
日期:——
We present a simple method for direct and solvent-free formation of amidesfromcarboxylicacids and amines using radiofrequency heating. The direct energy coupling of the AC magnetic field via nickel ferrite magnetic nanoparticles enables fast and controllable heating, as well as enabling facile work-up via magnetic separation.
A protocol for amide bond formation with electron deficient amines and sterically hindered substrates
作者:Maria E. Due-Hansen、Sunil K. Pandey、Elisabeth Christiansen、Rikke Andersen、Steffen V. F. Hansen、Trond Ulven
DOI:10.1039/c5ob02129d
日期:——
A protocol for amide coupling by in situ formation of acyl fluorides and reaction with amines at elevated temperature has been developed and found to be efficient for coupling of sterically hindered substrates and electron deficient amines where standard methods failed.
Bifunctional N,N‘-dioxide catalysts have been developed for highly enantioselective cyanosilylation of α,α-dialkoxy ketones. This process, catalyzed by in-situ-prepared proline-derived N,N‘-dioxide 2b, produced the corresponding cyanohydrin trimethylsilyl ethers in excellent yields (up to 99%) with high enantioselectivities (up to 93% ee). A reasonable mechanism was proposed according to the observation
双官能N,N- '二氧化物催化剂已经被开发用于α的高度对映选择性的硅氰化反应,α二烷氧基酮。此过程中,通过催化的原位制备的脯氨酸衍生Ñ,Ñ '二氧化物2b中,所产生的相应的氰醇三甲基甲硅烷基醚以优良产率(高达99%)的高对映选择性(高达93%ee)的。根据线性效应,1 H NMR谱图,分离的氰醇以及催化剂的NH和N-氧化物部分的作用,提出了合理的机理。