Hydrogen bond directed epoxidation: diastereoselective olefinic oxidation of allylic alcohols and amines

Davies, Stephen G.; Fletcher, Ai M.; Thomson, James E.

doi:10.1039/c4ob00616j

Cited by 29 publications

(18 citation statements)

References 48 publications

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“…Actually, many transition-metal complexes (such as those of Re, W, V, Nb, etc.) promoted the epoxidation of allylic alcohols by following the mechanism of hydrogen bonding, where the metal complexes play the role of a hydrogen bonding acceptor and the OH group of allylic alcohols acts as a hydrogen bonding donor. − …”

Section: Resultsmentioning

confidence: 99%

Role of Organic Fluoride Salts in Stabilizing Niobium Oxo-Clusters Catalyzing Epoxidation

Zhou

Tang

et al. 2021

Langmuir

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We present here that easily available organic salts can stabilize/modify niobium (Nb) oxo-clusters. The as-synthesized Nb oxo-clusters have been characterized by various methods. These Nb oxo-clusters were catalytically active for the epoxidation of allylic alcohols and olefins with H2O2 as an oxidant. Notably, Nb-OC@TBAF-0.5 appeared as highly dispersed nanosized particles and showed the highest catalytic activity, which can be attributed to the following reasons on the basis of characterization. First, the strong coordination of fluorine ions with Nb sites and the steric protection with bulky organic cations led to high stabilization and dispersion of the oxo-clusters in the course of the reaction. Second, a hydrogen-bond interaction between the coordinated fluorine atom and the −OH group of allylic alcohol favored the epoxidation reaction. Third, the electron density of Nb sites decreased due to the strong electron-withdrawing ability of F– adjacent to Nb sites, thus promoting the electrophilic oxygen transfer to the CC bond.

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Section: Resultsmentioning

confidence: 99%

Role of Organic Fluoride Salts in Stabilizing Niobium Oxo-Clusters Catalyzing Epoxidation

Zhou

Tang

et al. 2021

Langmuir

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“…Treatment of 13 with m- CPBA at room temeprature in dichloromethane gave epoxide 14 in 83% yield as a single diastereoisomer, as a result of steering by hydrogen bonding by either of the two allylic alcohols (Scheme ). The relative configuration of 14 was confirmed by the observation of strong NOE correlations of H9 with each of the C8 methyl group, H3, H5, and H7.…”

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confidence: 85%

Synthesis of Bradyrhizose from d-Glucose

Ngoje

Crich

2019

Org. Lett.

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We describe the synthesis of the unusual bicyclic sugar bradyrhizose in 14 steps and 6% overall yield from D-glucose. The synthesis involves the elaboration of a trans-fused carbocyclic ring onto the pre-existing glucopyranose framework followed by adjustment of the oxidation levels. Key steps include radical extension of the glucopyranose side chain, ring closing metathesis, allylic oxidation, Luche reduction, hydroxy-directed epoxidation and acid-catalyzed epoxide opening at the more substituted position.

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“…We have recently reported the asymmetric synthesis of (À)-isoretronecanol and (À)-trachelantamidine by employing the diastereoselective conjugate addition 11 of enantiopure lithium (S)-N-benzyl-N-(a-methylbenzyl)amide to an a,b-unsaturated ester followed by enolate allylation as the key stereodefining steps. Olefinic oxidation 12, 13 and reduction with LiAlH 4 allowed construction of the pyrrolizidine motif via a two-step protocol involving oxidative cleavage of the resultant 1,2-diol followed by onepot hydrogenolysis and double reductive cyclisation of the corresponding aldehyde to give (À)-isoretronecanol and (À)-trachelantamidine as single diastereoisomers. 14,15 Following a related approach, we envisaged that 1-hydroxymethyl-7-hydroxy substituted pyrrolizidines 17 could be efficiently accessed via the double reductive cyclisation of bisaldehyde 16 (X¼CO 2 t Bu or CH 2 OH), which could be directly derived from olefinic oxidation (such as ozonoylsis) of diastereoisomerically pure dienyl b-amino ester 14 or the corresponding alcohol 15.…”

Section: Introductionmentioning

confidence: 99%

Asymmetric syntheses of (−)-hastanecine, (−)-turneforcidine and (−)-platynecine

et al. 2016

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a b s t r a c tConcise total asymmetric syntheses of three diastereoisomeric 1-hydroxymethyl-7-hydroxy substituted pyrrolizidines, (À)-hastanecine, (À)-turneforcidine and (À)-platynecine, are reported. The doubly diastereoselective conjugate additions of lithium (R)-or (S)-N-benzyl-N-(a-methylbenzyl)amide to tertbutyl (R,E)-4-(triethylsilyloxy)hepta-2,6-dienoate [which was prepared (in 96:4 e.r.) via Lewis acid mediated catalytic asymmetric allylation of tert-butyl (E)-4-oxobut-2-enoate] proceeded in both cases under the dominant control of the lithium amide reagent. Subsequent diastereoselective enolate allylations installed the required stereogenic centres, and the pyrrolizidine ring system was rapidly accessed by a two-step protocol (viz. ozonolysis and one-pot hydrogenolysis/double reductive cyclisation), to complete the asymmetric syntheses of (À)-hastanecine, (À)-turneforcidine and (À)-platynecine in 17, 8 and 24% overall yield, respectively, in eleven steps from commercially available 2,2-dimethoxyacetaldehyde in each case.

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Hydrogen bond directed epoxidation: diastereoselective olefinic oxidation of allylic alcohols and amines

Cited by 29 publications

References 48 publications

Role of Organic Fluoride Salts in Stabilizing Niobium Oxo-Clusters Catalyzing Epoxidation

Role of Organic Fluoride Salts in Stabilizing Niobium Oxo-Clusters Catalyzing Epoxidation

Synthesis of Bradyrhizose from d-Glucose

Asymmetric syntheses of (−)-hastanecine, (−)-turneforcidine and (−)-platynecine

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