- Asymmetric Catalytic Vinylogous Addition Reactions Initiated by Meinwald Rearrangement of Vinyl Epoxides
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The first catalytic asymmetric multiple vinylogous addition reactions initiated by Meinwald rearrangement of vinyl epoxides were realized by employing chiral N,N′-dioxide/ScIII complex catalysts. The vinyl epoxides, as masked β,γ-unsaturated aldehydes, via direct vinylogous additions with isatins, 2-alkenoylpyridines or methyleneindolinones, provided a facile and efficient way for the synthesis of chiral 3-hydroxy-3-substituted oxindoles, α,β-unsaturated aldehydes and spiro-cyclohexene indolinones, respectively with high efficiency and stereoselectivity. The control experiments and kinetic studies revealed that the Lewis acid acted as dual-tasking catalyst, controlling the initial rearrangement to match subsequent enantioselective vinylogous addition reactions. A catalytic cycle with a possible transition model was proposed to illustrate the reaction mechanism.
- Dong, Shunxi,Feng, Xiaoming,He, Jun,Lin, Lili,Song, Yanji,Xu, Jinxiu
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- Catalytic Friedel-Crafts Reactions on Saturated Heterocycles and Small Rings for sp3-sp2 Coupling of Medicinally Relevant Fragments
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gem-Diarylheterocycles display a wide range of biological activity. Here we present a systematic study into the formation of 4- to 6-membered O- and N-heterocycles and cyclobutanes bearing the diaryl motif through a catalytic Friedel–Crafts reaction from the corresponding benzylic alcohols. 3,3-Diaryltetrahydrofurans, 4,4-diaryltetrahydropyrans, 3,3-diarylpyrrolidines, 4,4-diaryl-piperidines, as well as diarylcyclobutanes are examined, with results for 3,3-diaryloxetanes and 3,3-diarylazetidines presented for comparison. Three catalytic systems are investigated for each substrate [Ca(II), Li(I) and Fe(III)], across preinstalled aromatic groups of differing electronic character. In most cases examined, the diaryl product is obtained directly from the alcohol with good yields using the most appropriate catalyst system. In the absence of a nucleophile, the olefins from the 5- and 6-membered substrates by elimination of water are obtained under the same reaction conditions.
- Croft, Rosemary A.,Dubois, Maryne A. J.,Boddy, Alexander J.,Denis, Camille,Lazaridou, Anna,Voisin-Chiret, Anne Sophie,Bureau, Ronan,Choi, Chulho,Mousseau, James J.,Bull, James A.
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p. 5385 - 5395
(2019/06/24)
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- New synthesis of 3-aryl-2,5-dihydrofurans
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We present a straightforward synthesis of 3-aryl-2,5-dihydrofurans by ring contraction of 4-aryl-3,6-dihydro-2H-pyrans with the repeated treatment of MCPBA and BF3-OEt2. The building block 3-aryltetrahydrofuran-3-carboxylic acid with
- Chang, Meng-Yang,Lin, Chun-Yu,Pai, Chun-Li
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p. 1941 - 1948
(2007/10/03)
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- Improvement in Olefin Metathesis Using a New Generation of Ruthenium Catalyst Bearing an Imidazolylidene Ligand: Synthesis of Heterocycles
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(Equation Presented) A number of heterocycles have been prepared in very good yields using 1,3-dimesitylimidazol-2-ylidene ruthenium benzylidene 1. This catalyst displays increased activity for ring-closing metathesis of some hindered heterodienes which d
- Briot, Anne,Bujard, Murielle,Gouverneur, Véronique,Nolan, Steven P.,Mioskowski, Charles
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p. 1517 - 1519
(2007/10/03)
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- Ring closing metathesis of phenyl-substituted dienes
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A series of phenyl-substituted heterodienes 2a-f and 6 was prepared and subjected to ring closing metathesis (RCM) to give differently phenyl- substituted dihydropyrroles and dihydrofuran.
- Bujard,Briot,Gouverneur,Mioskowski
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p. 8785 - 8788
(2007/10/03)
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