Organocatalytic Michael Addition of Malonates to Isatylidene‐3‐acetaldehydes: Application to the Total Synthesis of (−)‐Debromoflustramine E

Liu, Renrong; Zhang, Junliang

doi:10.1002/chem.201300977

Cited by 45 publications

(12 citation statements)

References 110 publications

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“…Although the X‐ray crystallographic analyses provided the solid‐state structures of the iminium ions 3 , 4 and of the enamine 5 , and taking into account some preliminary calculations and previously published NMR analyses,10 the detailed overall conformational space and dynamic behaviors of these species still remain unclear. There are a couple of reports with diphenylmethyl silyl ether 2 as a catalyst: Zhang and Liu12 and Pihko et al 13. reported moderate enantioselectivity in the Michael reaction of malonate and isatylidene‐3‐acetaldehyde, and in the Mukaiyama–Michael reaction of methacrolein and 5‐methylsiloxyfuran, respectively, whereas Melchiorre and co‐workers14 obtained excellent enantioselectivity in the γ‐alkylation of a branched enal.…”

Section: Introductionmentioning

confidence: 99%

A Theoretical and Experimental Study of the Effects of Silyl Substituents in Enantioselective Reactions Catalyzed by Diphenylprolinol Silyl Ether

Hayashi

Okamura

Yamazaki

et al. 2014

Chemistry A European J

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The effect of silyl substituents in diphenylprolinol silyl ether catalysts was investigated. Mechanistically, reactions catalyzed by diphenylprolinol silyl ether can be categorized into three types: two that involve an iminium ion intermediate, such as for the Michael-type reaction (type A) and the cycloaddition reaction (type B), and one that proceeds via an enamine intermediate (type C). In the Michael-type reaction via iminium ions (type A), excellent enantioselectivity is realized when the catalyst with a bulky silyl moiety is employed, in which efficient shielding of a diastereotopic face of the iminium ion is directed by the bulky silyl moiety. In the cycloaddition reaction of iminium ions (type B) and reactions via enamines (type C), excellent enantioselectivity is obtained even when the silyl group is less bulky and, in this case, too much bulk reduces the reaction rate. In other cases, the yield increases when diphenylprolinol silyl ethers with bulky substituents are employed, presumably by suppressing side reactions between the nucleophilic catalyst and the reagent. The conformational behaviors of the iminium and enamine species have been determined by theoretical calculations. These data explain the effect of the bulkiness of the silyl substituent on the enantioselectivity and reactivity of the catalysts.

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Section: Introductionmentioning

confidence: 99%

A Theoretical and Experimental Study of the Effects of Silyl Substituents in Enantioselective Reactions Catalyzed by Diphenylprolinol Silyl Ether

Hayashi

Okamura

Yamazaki

et al. 2014

Chemistry A European J

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“…With this in mind, we wondered whether the combination of isatin-derived enals [7] and NHC-catalysis [8] together with aza-o-quinone methides or azoalkenes,w hich can be readily generated in situ from N-(ortho-chloromethyl)aryl amides [9] or a-halogeno hydrazones, [6g, 10] respectively,can open adirect [3+ +4] annulation entry for the asymmetric synthesis of spirobenzazepinones and spiro-1,2-diazepinones bearing an oxindole moiety connected through the spirocenter. Herein, we report the first procedure for the NHC-catalyzed enantioand atroposelective synthesis of the title spiro heterocycles.…”

mentioning

confidence: 99%

Asymmetric Synthesis of Spirobenzazepinones with Atroposelectivity and Spiro‐1,2‐Diazepinones by NHC‐Catalyzed [3+4] Annulation Reactions

et al. 2016

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A strategy for the NHC-catalyzed asymmetric synthesis of spirobenzazepinones, spiro-1,2-diazepinones, and spiro-1,2-oxazepinones has been developed via [3+4]-cycloaddition reactions of isatin-derived enals (3C component) with in-situ-generated aza-o-quinone methides, azoalkenes, and nitrosoalkenes (4atom components). The [3+4] annulation strategy leads to the seven-membered target spiro heterocycles bearing an oxindole moiety in high yields and excellent enantioselectivities with a wide variety of substrates. Notably, the benzazepinone synthesis is atroposelective and an all-carbon spiro stereocenter is generated.

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“…Communications 8518 www.angewandte.org and investigated the effect of the configuration of 1a on the reaction with 2a.Interestingly,the reaction of pure (Z)-1a [14] and pure (E)-1a [14] led to the spirocyclicp roduct 4a with comparable results and only aslight impact in terms of yield and enantioselectivity was observed (Scheme 2). Consequently,as elective synthesis of the enal 1 is not necessary as areadily available E/Z mixture is sufficient.…”

Section: Angewandte Chemiementioning

confidence: 88%

Switchable Access to Different Spirocyclopentane Oxindoles by N‐Heterocyclic Carbene Catalyzed Reactions of Isatin‐Derived Enals and N‐Sulfonyl Ketimines

et al. 2017

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Anovel NHC-catalyzed annulation protocol for the asymmetric synthesis of biologically important b-lactam fused spirocyclopentane oxindoles with four contiguous stereocenters,i ncluding two quaternary carbon centers,w as developed. Alternatively,s pirocyclopentane oxindoles containing an enaminone moiety can be achieved using the same starting materials,isatin-derived enals,and N-sulfonyl ketimines,inthe presence of as lightly different NHC catalytic system. This switchable annulation strategy enables the selective assembly of both heterocyclic scaffolds with good yields and excellent enantioselectivities for abroad range of substrates. AngewandteChemie Communications Scheme 2. The effect of the double-bondconfiguration of the isatinderived enal 1a on the synthesis of the spirocyclopentane oxindole 4a. DCE = 1,2-dichloroethane. Scheme 3. Synthetic transformations of the related spiroheterocycles 3a and 4a.T HF = tetrahydrofuran.Scheme 4. Postulated mechanism for the switchable asymmetric NHCcatalyzed reaction. (Ar = 2,6-Et 2 C 6 H 3 ).

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Organocatalytic Michael Addition of Malonates to Isatylidene‐3‐acetaldehydes: Application to the Total Synthesis of (−)‐Debromoflustramine E

Cited by 45 publications

References 110 publications

A Theoretical and Experimental Study of the Effects of Silyl Substituents in Enantioselective Reactions Catalyzed by Diphenylprolinol Silyl Ether

A Theoretical and Experimental Study of the Effects of Silyl Substituents in Enantioselective Reactions Catalyzed by Diphenylprolinol Silyl Ether

Asymmetric Synthesis of Spirobenzazepinones with Atroposelectivity and Spiro‐1,2‐Diazepinones by NHC‐Catalyzed [3+4] Annulation Reactions

Switchable Access to Different Spirocyclopentane Oxindoles by N‐Heterocyclic Carbene Catalyzed Reactions of Isatin‐Derived Enals and N‐Sulfonyl Ketimines

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