Enantioselective synthesis of α-bromo acid derivatives and bromohydrins † from tartrate derived bromoacetals

Boyes, Scott A.; Hewson, Alan T.

doi:10.1039/b002106g

Cited by 12 publications

(6 citation statements)

References 13 publications

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“…In particular, we considered that oxidation of the C aryl −C carbonyl bond would provide a broader selection of 1,4-dicarbonyl compounds with more flexibility for subsequent manipulation. Such Baeyer−Villiger reactions of (methoxyphenyl)ketones in conjunction with asymmetric synthesis are well-documented. − Indeed, exposure of 12a and 12j to m -chloroperbenzoic acid ( m -CPBA) in chloroform resulted in oxidation of the ketones to the derived p -methoxyphenyl (PMP) esters 13a and 13j , respectively (eq 3). As expected, no loss in optical purity was observed for the ester products.…”

Section: Resultsmentioning

confidence: 99%

Metallophosphite-Catalyzed Asymmetric Acylation of α,β-Unsaturated Amides

et al. 2006

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The l-menthone-derived TADDOL phosphite 6b catalyzes highly enantioselective conjugate additions of acyl silanes to α,β-unsaturated amides. p-Methoxybenzoyl cyclohexyldimethylsilane adds to a variety of N,N-dimethyl acrylamide derivatives in the presence of the lithium salt of 6b. In many instances the α-silyl-γ-ketoamide product undergoes facile enantioenrichment (to 97-99% ee) upon recrystallization. Desilylation with HF·pyr affords the formal Stetter addition products. BaeyerVilliger oxidation of the desilylated γ-ketoamides affords useful ester products. An X-ray diffraction study of 6b reveals that the isopropyl group of the menthone ketal influences the position of the synpseudoaxial phenyl group in the TADDOL structure. Through a crossover experiment, the silicon migration step in the reaction mechanism is shown to be strictly intramolecular.

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Section: Resultsmentioning

confidence: 99%

Metallophosphite-Catalyzed Asymmetric Acylation of α,β-Unsaturated Amides

et al. 2006

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“…The DPM group was easily removed with TiCl 4 (20 min, CH 2 Cl 2 , −78°, 91%) to give hydroxy ketone 13 . Alternatives to m -CPBA ( m- chloroperbenzoic acid), the standard reagent for Baeyer−Villiger oxidation, were investigated for the formation of the aryl ester. It was important to use conditions that would not give epoxidation of alkene-containing substrates.…”

Section: Resultsmentioning

confidence: 99%

Asymmetric Phase-Transfer Catalyzed Glycolate Alkylation, Investigation of the Scope, and Application to the Synthesis of (−)-Ragaglitazar

et al. 2005

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[Reaction: see text]. Asymmetric glycolate alkylation using a protected acetophenone surrogate under solid-liquid phase-transfer conditions is a new approach to the synthesis of 2-hydroxy esters and acids. Diphenylmethyloxy-2,5-dimethoxyacetophenone 1 with a trifluorobenzyl cinchonidinium bromide catalyst 9 (10 mol %) and cesium hydroxide provided S-alkylation products 2 at -35 degrees C in high yield (80-99%) and with excellent enantioselectivities using a wide range of electrophiles (80-90% ee). Alkylated products were elaborated to useful alpha-hydroxy intermediates 3 using bis-TMS peroxide Baeyer-Villiger conditions and selective transesterification reactions. The ester products have been enantioenriched by simple recrystallization from ether to give a single isomer (99% ee). A tight ion-pair model is proposed for the observed S-stereoinduction that includes van der Waals contacts between the extended enolate and the isoquinoline of the catalyst. To demonstrate the utility of the new methodology, the anti-diabetes drug (-)-ragaglitazar 24 was synthesized in six steps from a key 2-alkoxy-3-p-phenoxypropionic acid 26 that was made using PTC glycolate alkylation.

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“…The acid‐catalyzed esterification of 1,3‐dibromopropanol19 gave only low yields (<5 %). More recently, Boyes and Hewson have reported20 the esterification of similar compounds by using N , N ‐dicyclohexylcarbodiimide (DCC) and 4‐dimethylaminopyridine (DMAP). After several trials, we managed to find reaction conditions, which gave an ester derivative 2 of 1,3‐dibromopropan‐2‐ol in reasonable yields.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of an Amino‐Functionalized Model of the Fe‐Only Hydrogenase Active Site

Sályi

Kritikos

Åkermark

et al. 2003

Chemistry A European J

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A dinuclear 2Fe2S mimic 6 of the active site of the Fe-only hydrogenases has been synthesized. Complex 6 contains a free amino group which enables linkage to a protein backbone or to a redox active species for the study of electron transfer processes in proteins or in supramolecular systems. The structures of the complex 6 and its Boc-protected precursor 5 could be verified by X-ray crystallography.

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Enantioselective synthesis of α-bromo acid derivatives and bromohydrins † from tartrate derived bromoacetals

Cited by 12 publications

References 13 publications

Metallophosphite-Catalyzed Asymmetric Acylation of α,β-Unsaturated Amides

Metallophosphite-Catalyzed Asymmetric Acylation of α,β-Unsaturated Amides

Asymmetric Phase-Transfer Catalyzed Glycolate Alkylation, Investigation of the Scope, and Application to the Synthesis of (−)-Ragaglitazar

Synthesis of an Amino‐Functionalized Model of the Fe‐Only Hydrogenase Active Site

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