Enantioselective Iodine(III)-Mediated Synthesis of α-Tosyloxy Ketones: Breaking the Selectivity Barrier

Basdevant, Benoit; Legault, Claude Y.

doi:10.1021/acs.orglett.5b02501

Cited by 63 publications

(33 citation statements)

References 55 publications

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“…While free propiophenone 48 provided almost racemic material, the use of the preformed acetyl enol ether 50 under closely related conditions generated a synthetically useful enantiomeric excess (Scheme ). An even more useful catalytic protocol was developed by the use of the iodine catalyst 11a , which provided 49 with enantiomeric excesses of up to 90% …”

Section: Enantioselective Catalysismentioning

confidence: 99%

Enantioselective Iodine(I/III) Catalysis in Organic Synthesis

et al. 2018

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Chiral aryliodine(III)r eagents have provided an advancedc oncept for enantioselective synthesis and catalysis.W ith the advent of chiral iodine(I/III) catalysis,m anyd ifferent structures have been explored in the area. Thec urrently most prominent catalyst design is based on ar esorcinol core and the attachment of two lactic side chainsb earing ester or amide groups.T his enables ap rivileged modular catalyst synthesis,i nw hich fine-tuning with respect to the specificr eaction requirement is straightforward. Thep resent overview summarizes the structural variation and optimization of such chiral aryliodine catalysts andd iscusses structural properties of the active iodine(III) catalyst states.T he status quo of enantioselective iodine(I/III) oxidation catalysis with respect to intramolecular and intermolecular reaction control is reviewed, and specific aspects of the individual catalytic cycles are discussed. 1I ntroduction 2C hiral Aryliodine Catalysts 3E nantioselective Catalysis 3.1 Catalytic DearomatizationReactions 3.2 Formal C(sp 3 )Functionalization 3.3 Difunctionalization of Alkenes 4C onclusionScheme 14. Aryliodine-catalyzede nantioselective intermolecular para-dearomatization of phenols and aniline.Scheme15. Aryliodine-catalyzed enantioselective intermolecular para-dearomatization by Maruoka.Scheme30. Catalytic enantioselective version of the aminofluorination reaction.Scheme 28. Enantioselectiveo xidative cyclization of w-alkenylcarboxylic acids.Scheme29. Catalytic intramolecular diaminationo fa lkenes.

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Section: Enantioselective Catalysismentioning

confidence: 99%

Enantioselective Iodine(I/III) Catalysis in Organic Synthesis

et al. 2018

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“…Following these promising results, stoichiometric and catalytic enantioselective conditions were developed to convert acetyl enol esters to their corresponding chiral non‐racemic α‐tosyloxy ketones . This development enabled our group to obtain these useful chiral building blocks with unprecedented enantioselectivities (Scheme ).…”

Section: Enol Substratesmentioning

confidence: 99%

Enol and Ynol Surrogates: Promising Substrates for Hypervalent Iodine Chemistry

Lauriers

Legault

2016

Asian J Org Chem

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This reviewisd edicated to Prof. Jean Lessard on the occasion of his 80th birthday Asian Abstract: In numerous iodine(III)-mediated methodologies that involve ketone compounds, the enol tautomer is expected to be the reactive species. In this context,t he exploration of enol and ynol surrogates as substrates is of great interest. Activated p-systems have been shown to exhibit interesting and highly exploitable behavior towardh ypervalent iodine reagents. This has led to the development of nu-merousu seful oxidativet ransformations. Enamines, enamides, enol derivatives, haloalkenes, and haloalkynes are all enol or ynol surrogates that are reactivet owards the most populari odanes and iodonium salts. This Focus Review will describep ast and on-going research involving these substrates to gain insighti nto the similarities and disparities observed in their reactivity profiles.The ORCID identification number(s) for the author(s) of this articlecan be found under http://dx.Scheme4.Proposed mechanism to explain 2 H-arizine formation and acetoxylation.Scheme5.Synthesis of 2-trifluoromethyloxazoles developed by Du, Zhao, and co-workers.Scheme6.Dichlorination of enaminesd evelopedbyZ hao, Du, and co-workers.Scheme7.Optimizedreductive conditionst oconvertthe dihaloimines to their corresponding enamines.

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“…Hence, ap ractical methodh as been developed by Legault et al,w ho converted enol acetates into a-oxytosyl ketonesw ith high enantioselectivities( up to 90 % ee). [13] However,t his protocol requires an excess of chiral iodoarene 1f,w hich is ad rawback from ap ractical and economic point of view.W hile enantioselective a-oxytosylations of carbonyl compounds are extensively described,e nantioselective a-oxygenations including other nucleophiles remain scarce in the literature. [7b] Surprisingly,t he a-acetoxylation of ketones is one of the least described a-oxygenation reactions although it is the oldesto fa ll hypervalent iodine(III)-mediated a-oxygenation reactions.…”

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confidence: 99%

“…Based on previous mechanisticp roposals, ac atalytic cycle for the iodine(III)-mediated preparation of compounds was suggested (Scheme 3). [13,15,18] Chiral iodoarene 7b (Ar*I)i so xidised with mCPBA to the active catalyst 6h,w hichi sa ctivated by boron trifluoridee therate. [19] The activation enables ar eaction with enol ether 4 to generate a-C-bound intermediate 8, followed by an S N 2r eaction to form the final product (R)-5 and to regenerate catalyst 7b.T he high enantioselectivities compared to the corresponding ketone 2 derives from the inaccessibility of an enolate-type oxygen-bound iodine(III) intermediate, in whichalong distance between the stereocentre of Ar* and the a-carbon does not allow an efficient stereoinduction.…”

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confidence: 99%

Hypervalent Iodine(III)‐Catalysed Enantioselective α‐Acetoxylation of Ketones

Wirth

Hokamp

2020

Chemistry A European J

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An enantioselective catalytic synthesis of α‐acetoxylated ketones through I(I)/I(III) catalysis using a resorcinol/lactamide‐based chiral iodoarene is reported. Catalyst turnover by in situ generation of the active iodine(III) derivative is achieved by oxidation with mCPBA in the presence of acetic acid. The prior transformation of ketones to easily accessible acetyl enol ethers is beneficial and yields up to 97 % with enantioselectivities up to 88 % ee are obtained using only low catalyst loadings of only 5 mol % under mild reaction conditions.

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Enantioselective Iodine(III)-Mediated Synthesis of α-Tosyloxy Ketones: Breaking the Selectivity Barrier

Cited by 63 publications

References 55 publications

Enantioselective Iodine(I/III) Catalysis in Organic Synthesis

Enantioselective Iodine(I/III) Catalysis in Organic Synthesis

Enol and Ynol Surrogates: Promising Substrates for Hypervalent Iodine Chemistry

Hypervalent Iodine(III)‐Catalysed Enantioselective α‐Acetoxylation of Ketones

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