Chiral Silanes via Asymmetric Hydrosilylation with Catalytic CuH

Lipshutz, Bruce H.; Tanaka, Naoki; Taft, Benjamin R.; Lee, Ching-Tien

doi:10.1021/ol0529593

Cited by 89 publications

(20 citation statements)

References 24 publications

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“…For example, we have previously demonstrated that nonracemically ligated copper hydride can reduce E or Z b-silylenoates to afford chiral bsilanes with excellent enantioselectivity. [31] Alternatively, these substrates can be used to construct stereochemically pure vinyl iodides. DIBAL-H reduction of 12 afforded the corresponding b-silyl allylic alcohol (82 %; Scheme 5).…”

Section: Methodsmentioning

confidence: 99%

Stereoselective Silylcupration of Conjugated Alkynes in Water at Room Temperature

et al. 2014

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Micellar catalysis enables copper-catalyzed silylcupration of a variety of electron-deficient alkynes, thereby providing access to isomerically pure E- or Z-β-silyl-substituted carbonyl derivatives. These reactions take place in minutes, afford high yields and stereoselectivity, and are especially tolerant of functional groups present in the substrates. The aqueous reaction medium has been successfully recycled several times, and a substrate/catalyst ratio of 10,000:1 has been documented for this methodology.

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Section: Methodsmentioning

confidence: 99%

Stereoselective Silylcupration of Conjugated Alkynes in Water at Room Temperature

et al. 2014

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“…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).…”

mentioning

confidence: 99%

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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“…By contrast, the SEGPHOS analogue (184) gave inferior results. 233 A highly enantioselective synthesis of α-dehydroamino acids (186) with a stereogenic centre at the γ -position has been developed, which employs a copper-catalysed ee asymmetric conjugate addition of diethylzinc to α,β-unsaturated imines (185) with the TADDOL-derived phosphoramidite (187) as a chiral ligand. 234 The reaction of allyl carbamates (189) with activated enones (188) catalysed by (Ph 3 P) 4 Pd in THF proceeded smoothly at room temperature to give the corresponding α,β-bis-adducts (190) in high yields.…”

Section: Mementioning

confidence: 99%

Addition Reactions: Polar Addition

Kočovský

2010

Organic Reaction Mechanisms · 2006

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Chiral Silanes via Asymmetric Hydrosilylation with Catalytic CuH

Cited by 89 publications

References 24 publications

Stereoselective Silylcupration of Conjugated Alkynes in Water at Room Temperature

Stereoselective Silylcupration of Conjugated Alkynes in Water at Room Temperature

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

Addition Reactions: Polar Addition

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