New Method for Introduction of a Silyl Group into α,β-Enones Using a Disilane Catalyzed by a Copper(I) Salt<sup>1</sup>

Ito, Hajime; Ishizuka, Tomoko; Tateiwa, Jun-ichi; Sonoda, Motohiro; Hosomi, Akíra

doi:10.1021/ja9822557

Cited by 65 publications

(28 citation statements)

References 18 publications

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Section: Resultsmentioning

confidence: 99%

“…Given the low price of phenanthroline, it was selected as the ligand of choice. Finally, the influence of the solvent was found to be crucial to activate the disilane, [5] and we were delighted to observe that, among the aprotic polar solvents tested, N,NЈ-dimethyl-N,NЈ-propylene urea (DMPU; Diphenyltetramethyldisilane (1a) was subjected to the previously optimized cleavage conditions by using Cu I salts [(CuOTf) 2 ·C 6 H 6 (5 mol-%), phenanthroline (7 mol-%), in DMPU at 100°C, overnight, followed by acidic workup using p-toluenesulfonic acid in water] to generate a nucleophilic silicon species, which was then trapped with several 1,4-acceptors such as sulfono, cyano, amido, and phosphonato groups ( Interestingly, the designed conditions could be extended to the use of alkynes, leading to a new route for the preparation of vinylsilanes (Table 3). [17] Hence, phenylbutynone allowed the formation of the corresponding silylated compound 6a in 74 % yield ( Table 3, Entry 1).…”

Section: Resultsmentioning

confidence: 99%

“…[1] Among the different methods, the metal-mediated conjugate addition of nucleophilic silicon is particularly attractive, because it leads to the formation of functionalized –-silyl carbonyl compounds. [2] Although the use of commercially available disilanes has been studied, the generation of nucleophilic silicon by activation of a Si–Si bond [3] from disilanes is limited to Pd- [4] and Cu-catalyzed [5] conjugate silylation of enones and enals. More recently, Scheidt reported an extension of this method to α,β-unsaturated esters, but that study was restricted to the case of highly electrophilic alkylidene malonates.…”

Section: Introductionmentioning

confidence: 99%

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Activation of Si–Si Bonds for Copper(I)‐Catalyzed Conjugate Silylation

Iannazzo

Molander

2012

Eur J Org Chem

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Several alkyl- and vinylsilanes were prepared through the copper(I)-catalyzed conjugate silylation of α,β-unsaturated compounds. Optimal reaction conditions were first investigated to realize the conjugate addition of a nucleophilic silicon species to poorly electrophilic acceptors such as phenylvinyl sulfone by cleavage of the Si–Si bond of a disilane reagent. The scope of this reaction was extended to various electrophiles bearing different electron-withdrawing groups and afforded the desired substituted alkyl- and vinylsilanes. Among the wide range of commercially available disilanes, the reactivities of alkyl-, aryl-, and ethoxydisilane were also examined.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Activation of Si–Si Bonds for Copper(I)‐Catalyzed Conjugate Silylation

Iannazzo

Molander

2012

Eur J Org Chem

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“…[7] Copper-catalyzed conjugate silyl transfer of disilanes has also been reported, but again only for a racemic series. [8] To date, the palladium-catalyzed enantioselective 1,4-disilylation [9] of acyclic enones using disilanes has remained the sole example (B!A, Scheme 1). [10] The importance of b-silyl carbonyl compound A (either as a masked aldol itself or as a functionalized precursor for the preparation of a-chiral silanes) [2b] has resulted in the development of alternative catalyst-controlled routes towards A.…”

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Rhodium‐Catalyzed Enantioselective Conjugate Silyl Transfer: 1,4‐Addition of Silyl Boronic Esters to Cyclic Enones and Lactones

2006

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Silicon connected to a stereogenic carbon atom is an important functional group in asymmetric synthesis. The synthetic equivalence of silicon and oxygen, which is achieved by the stereospecific oxidative degradation of a C À Si bond, [1] as well as several stereoselective C À C bond-forming reactions involving a-chiral silanes [2] underscore the synthetic potential of silicon. Conversely, the number of effective methods for the direct enantioselective formation of CÀSi bonds is limited [3] and, therefore, novel asymmetric transition-metalcatalyzed reactions will certainly plug a "synthetic hole".The 1,4-addition of stoichiometric amounts of siliconbased cuprate reagents to prochiral a,b-unsaturated carbonyl compounds is one of the standard C À Si bond-forming reactions.[4] Although copper-catalyzed variants are available today, [5,6] their extension to chirally modified catalysts has so far failed. [7] Copper-catalyzed conjugate silyl transfer of disilanes has also been reported, but again only for a racemic series.[8] To date, the palladium-catalyzed enantioselective 1,4-disilylation [9] of acyclic enones using disilanes has remained the sole example (B!A, Scheme 1).[10] The importance of b-silyl carbonyl compound A (either as a masked aldol itself or as a functionalized precursor for the preparation of a-chiral silanes) [2b] has resulted in the development of alternative catalyst-controlled routes towards A. These approaches, however, rely on the more established rhodiumcatalyzed enantioselective formation of CÀC bonds [11] (C!A, Scheme 1) and copper-catalyzed enantioselective formation of CÀH bonds [12] (D!A, Scheme 1).[13]Inspired by the rhodium-catalyzed 1,4-addition of aryl boronic acids, [14] and aware of the diverse transition-metalcatalyzed chemistry of Si À B compounds, [15] we envisioned a rhodium-catalyzed (asymmetric) conjugate silyl transfer through the use of silyl boronic esters as the silyl anion source.[16] Herein we report an unprecedented conjugate CÀSi bond-forming reaction, which, for the first time, enables the catalytic asymmetric 1,4-addition of nucleophilic silicon to cyclic a,b-unsaturated carbonyl compounds with excellent levels of stereoinduction.Our search for catalysts that would facilitate silyl transfer from pinacol-derived silyl boronic ester 11[17] to 2-cyclohexenone (2) commenced with a systematic screening of rhodium (pre)catalysts (Scheme 2 and Table 1). For this, typical reaction conditions for the rhodium-catalyzed 1,4-addition of aryl boronic acids served as a reasonable reference point (1,4-dioxane/H 2 O solvent mixtures at elevated reaction temperatures).[14] Two crucial observations emerged from these initial investigations: Both the presence of a base and the absence of strongly coordinating counterions were critical for product formation. Replacement of chloride by weakly or noncoordinating perchlorate led to the achiral cationic catalyst [(dppp)Rh(cod)]ClO 4 . [18] We were pleased to find that a combination of this catalyst (5.0 mol %) and an equimolar amount of the...

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“…[7] Der kupferkatalysierte konjugierte Silyltransfer ausgehend von Disilanen wurde ebenfalls nur für den racemischen Fall verwirklicht. [8] Noch immer ist die palladiumkatalysierte enantioselektive 1,4-Disilylierung [9] von acyclischen Enonen unter der Verwendung von Disilanen ein Einzelfall (B!A, Schema 1). [10] Vor dem Hintergrund der Bedeutung b-silylierter Carbonylverbindungen A…”

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Rhodiumkatalysierter enantioselektiver konjugierter Silyltransfer: 1,4‐Addition von Silylboronsäureestern an cyclische Enone und Lactone

2006

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New Method for Introduction of a Silyl Group into α,β-Enones Using a Disilane Catalyzed by a Copper(I) Salt¹

Cited by 65 publications

References 18 publications

Activation of Si–Si Bonds for Copper(I)‐Catalyzed Conjugate Silylation

Activation of Si–Si Bonds for Copper(I)‐Catalyzed Conjugate Silylation

Rhodium‐Catalyzed Enantioselective Conjugate Silyl Transfer: 1,4‐Addition of Silyl Boronic Esters to Cyclic Enones and Lactones

Rhodiumkatalysierter enantioselektiver konjugierter Silyltransfer: 1,4‐Addition von Silylboronsäureestern an cyclische Enone und Lactone

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New Method for Introduction of a Silyl Group into α,β-Enones Using a Disilane Catalyzed by a Copper(I) Salt1

Cited by 65 publications

References 18 publications

Activation of Si–Si Bonds for Copper(I)‐Catalyzed Conjugate Silylation

Activation of Si–Si Bonds for Copper(I)‐Catalyzed Conjugate Silylation

Rhodium‐Catalyzed Enantioselective Conjugate Silyl Transfer: 1,4‐Addition of Silyl Boronic Esters to Cyclic Enones and Lactones

Rhodiumkatalysierter enantioselektiver konjugierter Silyltransfer: 1,4‐Addition von Silylboronsäureestern an cyclische Enone und Lactone

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New Method for Introduction of a Silyl Group into α,β-Enones Using a Disilane Catalyzed by a Copper(I) Salt¹