Chelation-controlled protocol for the diastereoselective reduction of ketones

Sarko, Christopher R.; Guch, I. C.; DiMare, Marcello

doi:10.1021/jo00083a004

Cited by 40 publications

(28 citation statements)

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“…The configuration of the product is consistent with hydride addition to the less hindered position predicted using the Felkin model [21]. Chelation-controlled reduction [22] of β-substituted enone 14 with Zn(BH 4 ) 2 provided syn-allylic alcohol 22 in excellent yield and diastereoselectivity. The configuration obtained can be rationalized by considering hydride addition to the less hindered axial position in a six-membered chelated-intermediate.…”

Section: Enantioselective Intermolecular Hydroacylation Reactions Empsupporting

confidence: 69%

Rhodium-catalyzed enantioselective intermolecular hydroacylation reactions

González-Rodrı́guez

Willis

2011

Pure and Applied Chemistry

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Rhodium-catalyzed enantioselective hydroacylation reactions allow rapid access to chiral substituted ketones. However, due to the low reactivity of disubstituted alkenes in intermolecular versions of this process, only a small number of asymmetric intermolecular reactions have been described. Strategies employed to avoid reactivity issues include the use of norbornadienes, linear dienes, acrylamides, and allenes as the alkene components. In addition, our laboratory has recently reported the rhodium-catalyzed enantioselective intermolecular alkyne hydroacylation reaction, leading to the formation of enone products via a kinetic resolution procedure.Scheme 1 An alkene hydroacylation reaction and the undesired decarbonylation process.Over the last several years, our laboratory has developed the use of β-S-chelating aldehydes as substrates for rhodium-catalyzed alkene and alkyne hydroacylation reactions (Scheme 2) [5]. The use of a β-sulfide group leads to the formation of a stabilized five-membered intermediate II, allowing hydroacylation reactions to proceed without decarbonylation under mild conditions and in high yields. The methodology has also been extended to include thioacetal-substituted aldehydes [6]. ENANTIOSELECTIVE INTERMOLECULAR HYDROACYLATION REACTIONSAlthough a number of achiral intermolecular hydroacylation reactions have now been described, reports of asymmetric reactions are still limited. This is in contrast to the intramolecular variant of the reaction, for which a number of highly efficient and selective reactions have been developed [7]. The first examples of these highly enantioselective cyclizations were described by both Sakai and Bosnich for the conversion of 4-pentenals (1) to give cyclopentanone products (2), catalyzed by chiral cationic rhodium complexes (Scheme 3) [8]. C. GONZÁLEZ-RODRÍGUEZ AND M. C. WILLIS © 2011, IUPAC 578 Scheme 2 Intermolecular Rh-catalyzed hydroacylation reactions using β-S-chelating aldehydes. Scheme 3 Asymmetric intramolecular alkene and alkyne hydroacylation reactions.

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Section: Enantioselective Intermolecular Hydroacylation Reactions Empsupporting

confidence: 69%

Rhodium-catalyzed enantioselective intermolecular hydroacylation reactions

González-Rodrı́guez

Willis

2011

Pure and Applied Chemistry

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“…This was then diastereoselectively reduced with borane/pyridine complex. [22] The obtained syn-diol was directly converted into its acetonide (+)-23 under standard conditions. Interestingly, treatment of (+)-23 with LiEt 3 BH in THF at -78°C allowed the selective reduction of its acetate moiety, with slower reduction of the enol isobutyrate moiety, leading to the alcohol (+)-24 in 75 % yield.…”

Section: Resultsmentioning

confidence: 99%

Efficient Asymmetric Synthesis of Long‐Chain Polyketides Containing up to Ten Contiguous Stereogenic Centres by Double Chain Elongation

et al. 2011

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The 2,3-anti-3,4-syn-stereotriad (1Z,2S,3R,4S)-1-ethylidene-2,4-dimethyl-3-[(1S)-1-phenylethoxy]-5-oxopent-1-yl isobutyrate {(-)-8, obtained in a one-pot operation from the trimethylsilyl (Z)-enol ether derived from pentan-3-one and (1E,3Z)-1[(1S)-phenylethoxy]-2-methylpenta-1,3-dien-3-yl isobutyrate through SO 2 umpolung} contains an ethyl ketone moiety that undergoes diastereoselective cross-aldol reactions with acetaldehyde. After subsequent reductions, various diastereomeric stereohexads (polypropionate fragments containing six contiguous stereogenic centres) in which the

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“…[14] Compounds 8 a ± e were synthesized by a standard procedure. [15] Compounds 8 f ± g were prepared according to standard methodology. [16] anti-b-Hydroxy ketones 11, 14, 17, and 20 were prepared in excellent diastereomeric purity (> 99 %) following the procedure reported by Brown.…”

Section: Resultsmentioning

confidence: 99%

The Role of theα-Stereogenic Center in the Control of Stereoselection in the Reduction ofα-Alkyl-β-hydroxy Ketones: A Highly Diastereoselective Protocol for the Synthesis of 1,2-syn-2-Alkyl-1,3-diols

et al. 2000

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Accurate investigations on the role played by an alpha-stereogenic center in controlling the reduction of various classes of beta-hydroxy ketones allowed us to set up a general and highly diastereoselective protocol for the synthesis of 2-alkyl-1,3-diols with 1,2-syn relationship. This methodology is based on the conversion of a beta-hydroxy ketone into the corresponding titanium alcoholate that permits us to organize the substrate in a stable and rigid structure, which stereofacially favors attacking hydride ions. The use of THF as solvent makes available a variety of hydride donors that cover a large spectrum of steric demand: the choice of the more appropriate one depends on the conformational stability of the cyclic intermediate. Excellent results are obtained also in the presence of an additional stereogenic center in the beta-position, even if it exerts a concordant or an opposite steric effect with respect to the alpha-substituent.

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Chelation-controlled protocol for the diastereoselective reduction of ketones

Cited by 40 publications

References 0 publications

Rhodium-catalyzed enantioselective intermolecular hydroacylation reactions

Rhodium-catalyzed enantioselective intermolecular hydroacylation reactions

Efficient Asymmetric Synthesis of Long‐Chain Polyketides Containing up to Ten Contiguous Stereogenic Centres by Double Chain Elongation

The Role of theα-Stereogenic Center in the Control of Stereoselection in the Reduction ofα-Alkyl-β-hydroxy Ketones: A Highly Diastereoselective Protocol for the Synthesis of 1,2-syn-2-Alkyl-1,3-diols

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