Highly Enantioselective Catalytic Ketone Allylation with Sn(CH2CH=CH2)4/RSn(CH2CH=CH2)3 Mixtures (R = Et, Bu)

Cunningham, Anthony; Woodward, Simon

doi:10.1055/s-2002-19323

Cited by 47 publications

(19 citation statements)

References 2 publications

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“…Under optimized condition with a 3/1/2 ratio of 101/ketone/(R)-BINOL and 2 equiv of MeOH, the allylation product 102 is obtained in high yield albeit modest enantioselectivity. Important improvements in enantioselectivity and chiral modifier loading are seen with the use of 1,1′-binaphthalen-2′-mercapto-2-ol 103 149 (Scheme 56). With 20 mol % of 103 and 40 mol % of water, a number of aryl ketones are allylated with a mixture of 101 and (triallyl)butylstannane (optimized ratio 7/3), to provide the adducts in high yields and enantioselectivities.…”

Section: Scheme 52mentioning

confidence: 99%

Catalytic Enantioselective Addition of Allylic Organometallic Reagents to Aldehydes and Ketones

2003

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Section: Scheme 52mentioning

confidence: 99%

Catalytic Enantioselective Addition of Allylic Organometallic Reagents to Aldehydes and Ketones

2003

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“…In fact, the allylation of different phenones using this chiral monothiol could be performed at room temperature and using substoichiometric amounts of the ligand without any further additive, the ee being up to 92% [113]. A mechanistic study showed the great impact of impurities on the enantioselectivity and as result of this study a tetrametallic species was postulated as the catalytic system.…”

Section: Allylation Processesmentioning

confidence: 84%

Alkylation of Ketones and Imines

Ramón

Yus

2005

Quaternary Stereocenters

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IntroductionAfter the disastrous incident of thalidomide, whose two enantiomers have totally different biological effects in humans [1], there is increasing public demand for the synthesis of chiral compounds. The responsibility of synthetic chemists is to prevent a repetition of this tragedy by providing highly efficient and reliable methods of asymmetric synthesis [2].All chiral compounds have at least one stereogenic element, which is usually a stereogenic center. Nowadays, the generation of tertiary carbon-atom stereocenters (carbon atoms bearing one hydrogen atom) can be easily achieved in most cases by using the appropriate chiral auxiliary, reagent or catalyst from the vast number of synthetic approaches. However, the related approach to complex compounds bearing quaternary stereocenters is still a challenge for synthetic organic chemistry, and every asymmetric procedure for the construction of a fully substituted carbon center is of great value [3]. In fact, the simple extension of methods from the preparation of tertiary stereocenters to the preparation of quaternary ones is not straightforward; in some cases, the interval between the two could be more than ten years, and the development may involve the use of new and different approaches.One of the most frequently occurring classes of compound in nature with a heterosubstituted quaternary center [4] is the corresponding tertiary alcohols and their related amine derivatives. Among the different approaches to the synthesis of this type of compound, such as kinetic resolution, asymmetric desymmetrization, oxidation processes, electrophilic alkylation and nucleophilic addition, those that involve stereoselective C-C bond formation are of particular interest, since one C-C bond and one stereoelement are created in a single synthetic step. In the case that engages our attention, the simplest conceptual approach for the preparation of chiral tertiary alcohols, and the relate amines, is the asymmetric 1,2-addition of organometallic reagents [5] to ketones, or to the corresponding imines. However, this approach has a central problem: the structural similarity between the two substituents around the electrophilic carbonyl group and therefore the Quaternary Stereocenters: Challenges and Solutions for Organic Synthesis. Edited

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“…up to 86%. 1 the COST-D24 Programme. We thank a referee for pointing out the possibility of catalysis by (MTB)Sn(allyl)R species.…”

Section: 2mentioning

confidence: 99%

“…In 2002 we identified an unusual asymmetric reaction where, in the presence of catalytic amounts of the chiral ligand MTBH 2 samples of tetraallyltin of 98% chemical purity ketones were allylated up to nine times more selectively than with completely pure Sn(CH 2 CH@CH 2 ) 4 (>99% purity gives <35% ee for PhC(O)Me) (Scheme 1) [1]. Subsequent careful work revealed the selective catalyst is formed from trace amounts of EtSnCl(CH 2 CH@CH 2 ) 2 (3) derived from incomplete reaction of the SnCl 4 and the presence of EtBr (used for Grignard preparation) [2].…”

Section: Introductionmentioning

confidence: 99%

Enantioselective catalytic allylation of arylmethylketones using tetraallyltin and tin(IV) chloride mixtures

Prieto¹,

Woodward²

2006

Journal of Organometallic Chemistry

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Highly Enantioselective Catalytic Ketone Allylation with Sn(CH2CH=CH2)4/RSn(CH2CH=CH2)3 Mixtures (R = Et, Bu)

Abstract: In the presence of the monothiobinaphthol (MTB) ligand aryl ketones are allylated by mixtures of Sn(CH 2 CH=CH 2 ) 4 / RSn(CH 2 CH=CH 2 ) 3 (R = Et, Bu) in high e.e. The presence of water suppresses racemic background allylation.

Cited by 47 publications

References 2 publications

Catalytic Enantioselective Addition of Allylic Organometallic Reagents to Aldehydes and Ketones

Catalytic Enantioselective Addition of Allylic Organometallic Reagents to Aldehydes and Ketones

Alkylation of Ketones and Imines

Enantioselective catalytic allylation of arylmethylketones using tetraallyltin and tin(IV) chloride mixtures

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