Stereoselective hetero Diels–Alder reactions of chiral tricarbonyl (η6-benzaldehyde)chromium complexes
摘要:
The ZnCl2-promoted cycloaddition of a series of enantiopure ortho-substituted benzaldehyde-Cr(CO), complexes and Danishefsky's diene gave the corresponding 2-aryl pyranones in good yields and complete enantio specificity. Some of the mechanistic aspects of the cycloaddition were investigated and the reaction extended to different dienes. (C) 2001 Elsevier Science Ltd. All rights reserved.
Chiral Chromium Salen@rGO as Multipurpose and Recyclable Heterogeneous Catalyst
作者:Mariam Abd El Sater、Mohamed Mellah、Diana Dragoe、Emilie Kolodziej、Nada Jaber、Emmanuelle Schulz
DOI:10.1002/chem.202101003
日期:2021.6.25
to promote asymmetric catalysis in repeated cycles, without loss of activity or enantioselectivity. This specific behavior was demonstrated in two different catalytic reactions (up to ten reuses) promoted by chromium salen complexes, the cyclohexene oxide ring-opening reaction and the hetero-Diels-Alder cycloaddition between various aldehydes and Danishefsky's diene. Furthermore, the chiral chromium
A Highly Enantioselective Hetero-Diels−Alder Reaction of Aldehydes with Danishefsky's Diene Catalyzed by Chiral Titanium(IV) 5,5‘,6,6‘,7,7‘,8,8‘-Octahydro-1,1‘-bi-2-naphthol Complexes
products with very high enantioselectivity (up to 99% ee) and yield (92%). The hetero-Diels-Alder reaction of other aldehydes with 1 under the catalysis of TiHBOL is a general reaction which proceeds well with very high enantioselectivity and isolated yield for various aldehydes at 0 degrees C to room temperature. Based on the experimental results, the proposed mechanism of the hetero-Diels-Alder reaction
A process for performing a catalytic Diels-Alder reaction by reacting a diene with a dienophile in the presence of a heterogeneous catalyst comprising a zeolitic material exchanged or impregnated with ions of a Lewis acidic metal is described. The catalyst, for example, copper-exchanged zeolite Y, may be treated with chiral bis(imine) compounds to direct the chirality of the reaction products. The catalyst can be separated from the reaction mixture and re-used in further Diels Alder reactions.
Highly efficient enantioselective synthesis of optically active dihydropyrones by chiral titanium(iv) (5,5′,6,6′,7,7′,8,8′-octahydro-1,1′-bi-2-naphthol) complexes
The asymmetric hetero-Diels–Alder reaction of Danishefsky’s diene and an aldehyde catalyzed by 20 mol% chiral H8-BINOL–Ti(IV) affords the corresponding 2-substitutent-2,3-dihydro-4H-pyran-4-one with ees of up to 99% under mild reaction conditions.
Optically active 3-oxobutylideneaminatocobalt(III) complexes were developed as effective catalysts for the enantioselective hetero Diels–Alder reaction of aromatic and aliphatic aldehydes with 3-(t-butyldimethylsilyloxy)-1-methoxy-1,3-butadiene. In the presence of the highly active cationic cobalt(III) complex, the hetero Diels–Alder reactions proceeded to afford the corresponding dihydropyran-4-ones