Aktivierung von Bor‐ und Siliciumreagentien bei stereokontrollierten Allylierungen

Kennedy, Jason W. J.; Hall, Dennis G.

doi:10.1002/ange.200301632

Cited by 75 publications

(18 citation statements)

References 36 publications

(24 reference statements)

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“…[161,196] The reaction was discovered in 1976, but only ten years later was the asymmetric multicomponent version published (Scheme 62). The first example used the complex formed by reaction of titanium [104] tetrachloride with two equivalents of lithium phenethyl alcoholate {129: Ar= Ph, R 2 = Me, X = Ti[(S)-OCHMePh]Cl 2 ).…”

Section: Asymmetric Sakurai Multicomponent Allylation Processmentioning

confidence: 99%

Asymmetric Multicomponent Reactions (AMCRs): The New Frontier

2005

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Asymmetric multicomponent reactions involve the preparation of chiral compounds by the reaction of three or more reagents added simultaneously. This kind of addition and reaction has some advantages over classic divergent reaction strategies, such as lower costs, time, and energy, as well as environmentally friendlier aspects. All these advantages, together with the high level of stereoselectivity attained in some of these reactions, will force chemists in industry as in academia to adopt this new strategy of synthesis, or at least to consider it as a viable option. The positive aspects as well as the drawbacks of this strategy are discussed in this Review.

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Section: Asymmetric Sakurai Multicomponent Allylation Processmentioning

confidence: 99%

Asymmetric Multicomponent Reactions (AMCRs): The New Frontier

2005

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“…A brief screening of Lewis acids revealed that SnA C H T U N G T R E N N U N G (OTf) 2 (Tf = triflate) at 50 mol % loading provided the best yields and diastereoselectivities. [14] The reaction offers a diverse substrate scope: as well as representative aromatic aldehydes 4 (Table 2, entries [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15], it also proved to work well with aliphatic (Table 2, entries 16, 17 and 20) and a,b-unsaturated aldehydes (Table 2, entry 18 and 19). …”

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confidence: 99%

“…[1] The resulting homoallylic alcohols 3 are popular building blocks in targetoriented synthesis. However, in contrast to the more widely known and better-developed boron analogues, the synthetic applications of allyltrichlorosilanes are currently limited to simple alkyl homologues (R 2 = alkyl).…”

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confidence: 99%

A Novel Bifunctional Allyldisilane as a Triple Allylation Reagent in the Stereoselective Synthesis of Trisubstituted Tetrahydrofurans

Malkov

Kysilka

Edgar

et al. 2011

Chemistry A European J

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Dedicated to Professor František Tureček on the occasion of his 60th birthdayLewis base catalysed enantioselective allylation of aldehydes 1 with allyltrichlorosilanes 2 (Scheme 1) has become an efficient tool for C À C bond formation, thereby providing a robust alternative to the use of allylboranes carrying stoichiometric amounts of chiral auxiliaries.[1] The resulting homoallylic alcohols 3 are popular building blocks in targetoriented synthesis. However, in contrast to the more widely known and better-developed boron analogues, the synthetic applications of allyltrichlorosilanes are currently limited to simple alkyl homologues (R 2 = alkyl). Recently, we have demonstrated that alcohols 3, resulting from the addition of g-substituted allylsilanes 2, can themselves serve as efficient allylating reagents for aldehydes 4, which has broadened the scope of the method considerably.[2] A further advancement can be achieved by attaching additional functionality to allylsilane 2, and thus to the resulting alcohol 3, that will enable further synthetic development.[3] Herein, we introduce the new bifunctional allyldisilane 6 and demonstrate its applicability in a highly stereoselective triple allylation of aldehydes, resulting in a stereocontrolled construction of trisubstituted tetrahydrofurans 8 (Scheme 2).The synthesis of allyldisilane 6 started from tetrahydropyranyl (THP)-protected propargyl alcohol 9 (Scheme 3), for which deprotonation with nBuLi, followed by alkylation with iodomethyltrimethylsilane, afforded trimethylsilyl (TMS) derivative 10 (83 %). After deprotection, the resulting alcohol was reduced with lithium aluminium hydride to give (E)-4-trimethylsilylbutenol 11 (47 % over two steps) as a pure stereoisomer. The conversion of alcohol 11 into the corresponding chloride 12 required a great deal of optimisation and the protocol employing N-chlorosuccinimide with triphenylphosphine turned out to be the most efficient, as it preserved the regio-and stereo-integrity and afforded the required allylic chloride 12 in good yield (80 %).[4] Finally, a CuCl-mediated coupling of 12 with trichlorosilane in the presence of an equimolar amount of the Hünig base [5] afforded the required allyldisilane (E)-6 (60 %) as a liquid, which can be used in situ or isolated by distillation.With the geometrically pure (E)-allyldisilane 6 in hand, we first explored a racemic variant of the allylation of aldehydes 1, employing DMF as the Lewis base activator (1-3 equiv). The reaction proceeded readily, producing ex- [a] O.

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“…[8a] The authors of the study have shown that aryl boronic acids may be accessed directly from aryl chloride substrates, and either isolated or derivatized further in situ to easy-to-handle trifluoroborate salts [9] 4 or corresponding boronate esters, such as 5 or 6 (Scheme 1). Thus, by slight variation of the reaction conditions different boronates (3)(4)(5) can be obtained for Suzuki-Miyaura coupling reactions, [2] and if necessary, the boronate group can be protected as a MIDA boronate [10] (6; MIDA = N-methyliminodiacetic acid) too.…”

mentioning

confidence: 99%

“…[3] Accordingly, the development of synthetic methods for the generation of organoboron species has attracted considerable interest. Several excellent and important approaches to this challenge have emerged, including the palladium-catalyzed borylation of haloarenes [4] and iridium-catalyzed aryl C À H borylation.…”

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confidence: 99%

Palladium‐Catalyzed Direct Synthesis of Organoboronic Acids

Pilarski

Szabó

2011

Angew Chem Int Ed

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Diboronic acid in the spotlight: Molander et al. have developed an excellent method for the direct synthesis of aryl boronic acids from aryl chlorides (see scheme). In this palladium‐catalyzed procedure, diboronic acid, a notably underutilized reagent, was used as the boron source. The boronic acid products can be isolated from the procedure, or used in one‐pot reactions to give a wide range of boronates and biaryls.

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Aktivierung von Bor‐ und Siliciumreagentien bei stereokontrollierten Allylierungen

Cited by 75 publications

References 36 publications

Asymmetric Multicomponent Reactions (AMCRs): The New Frontier

Asymmetric Multicomponent Reactions (AMCRs): The New Frontier

A Novel Bifunctional Allyldisilane as a Triple Allylation Reagent in the Stereoselective Synthesis of Trisubstituted Tetrahydrofurans

Palladium‐Catalyzed Direct Synthesis of Organoboronic Acids

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