Cyanosilylation Of Ketones Research Articles

Lewis Acid Rather than Brønsted Acid Sites of Montmorillonite K10 Act as a Powerful and Reusable Green Heterogeneous Catalyst for Rapid Cyanosilylation of Ketones

A practical green protocol was developed for highly efficient cyanosilylation of various ketones catalyzed by commercial montmorillonite K10, with excellent isolated yields (91–99%). The catalyst can be used as received, and its catalytic strength can be easily restored without loss of activity. Investigations of catalyst recycling and of the active catalytic sites indicated that Lewis acid sites were mainly responsible for the cyanosilylation of ketones.

ChemInform Abstract: Me2(CH2Cl)SiCN: Bifunctional Cyanating Reagent for the Synthesis of Tertiary Alcohols with a Chloromethyl Ketone Moiety via Ketone Cyanosilylation.

AbstractA novel bifunctional silyl reagent is introduced for highly enantioselective cyanosilylation of ketones.

Me2(CH2Cl)SiCN: Bifunctional Cyanating Reagent for the Synthesis of Tertiary Alcohols with a Chloromethyl Ketone Moiety via Ketone Cyanosilylation.

We report a novel bifunctional cyanating reagent, Me2(CH2Cl)SiCN, which paves the way to a one-pot sequential synthesis of tertiary alcohols featuring a chloromethyl ketone moiety via enantioselective ketone cyanosilylation. This method contributes to gram-scale enantioselective total synthesis of the aggregation pheromone of the Colorado potato beetle, (S)-CPB.

ChemInform Abstract: Enantioselective Cyanosilylation of Ketones with Lithium(I) Dicyanotrimethylsilicate(IV) Catalyzed by a Chiral Lithium(I) Phosphoryl Phenoxide.

A highly enantioselective cyanosilylation of ketones was developed by using a chiral lithium(I) phosphoryl phenoxide aqua complex as an acid/base cooperative catalyst. The pentacoordinate silicate generated in situ from Me3SiCN/LiCN acts as an extremely reactive cyano reagent. Described is a 30 gram scale reaction and the synthesis of the key precursor to (+)-13-hydroxyisocyclocelabenzine.

ChemInform Abstract: Activation of Chiral (Salen)AlCl Complex by Phosphorane for Highly Enantioselective Cyanosilylation of Ketones and Enones.

AbstractThe high efficiency of this reaction relies on orthogonal activation of the AlCl(salen) complex and Tms—CN by the phosphorane and POPh3, respectively.

Enantioselective Cyanosilylation of Ketones with Lithium(I) Dicyanotrimethylsilicate(IV) Catalyzed by a Chiral Lithium(I) Phosphoryl Phenoxide

AbstractA highly enantioselective cyanosilylation of ketones was developed by using a chiral lithium(I) phosphoryl phenoxide aqua complex as an acid/base cooperative catalyst. The pentacoordinate silicate generated in situ from Me3SiCN/LiCN acts as an extremely reactive cyano reagent. Described is a 30 gram scale reaction and the synthesis of the key precursor to (+)‐13‐hydroxyisocyclocelabenzine.

Enantioselective Cyanosilylation of Ketones with Lithium(I) Dicyanotrimethylsilicate(IV) Catalyzed by a Chiral Lithium(I) Phosphoryl Phenoxide.

A highly enantioselective cyanosilylation of ketones was developed by using a chiral lithium(I) phosphoryl phenoxide aqua complex as an acid/base cooperative catalyst. The pentacoordinate silicate generated in situ from Me3SiCN/LiCN acts as an extremely reactive cyano reagent. Described is a 30 gram scale reaction and the synthesis of the key precursor to (+)-13-hydroxyisocyclocelabenzine.

Activation of Chiral (Salen)AlCl Complex by Phosphorane for Highly Enantioselective Cyanosilylation of Ketones and Enones.

Phosphoranes 2 are identified as a class of effective Lewis bases to activate chiral (salen)AlCl complex 1 to enhance its electrophilicity. Accordingly, a three-component catalyst system consisting of complex 1, phosphorane 2e, and Ph3PO is developed as a powerful tool for asymmetric ketone cyanosilylation. In particular, an unprecedented highly enantioselective cyanosilylation of linear aliphatic ketones is achieved. A tandem Wittig-cyanosilylation sequence starting from phosphorane 2a and enals 10 is further achieved, which internally utilizes the Ph3PO byproduct and remaining phosphorane 2a as cocatalysts for cyanosilylation of α,β,γ,δ-unsaturated enones, providing atom-efficient access to valuable chiral conjugated dienes and enynes. The high efficiency of the cyanosilylation originates from orthogonal activation of both (salen)AlCl complex 1 and cyanotrimethylsilane by the phosphorane and Ph3PO, respectively. This mechanistic insight is supported by NMR, MS, and ReactIR analyses and DFT calculations. Furthermore, the formation of charged complexes through the activation of chiral complex 1 by phosphorane 2a is confirmed by electrical conductivity experiments.

Toward understanding the structure–catalyst activity relationship of new indium MOFs as catalysts for solvent-free ketone cyanosilylation

The evidence of highly reactive behavior of four new recyclable and environmental benign indium metal–organic frameworks, MOFs, as Lewis acid catalysts in the solvent-free cyanosilylation of carbonyl compounds.

Synthesis, Characterization, and Reactivity of Lanthanide Amides Incorporating Neutral Pyrrole Ligand. Isolation and Characterization of Active Catalyst for Cyanosilylation of Ketones

A series of lanthanide amido complexes incorporating a neutral pyrrole ligand were synthesized and characterized, and their catalytic activities were studied. Treatment of [(Me3Si)2N]3Ln(μ-Cl)Li(THF)3 with 1 equiv of [(2,5-Me2C4H2N)CH2CH2] 2NH (1) in toluene afforded the corresponding lanthanide amides with the formula [η5:η1-(2,5-Me2C4H2N)CH2CH2]2NLn[N(SiMe3)2]2 (Ln = La (2), Nd (3)). Reaction of 2 or 3 with N,N′-dicyclohexylcarbodiimide (CyN═C═NCy) gave the carbodiimide selectively inserted into the appended Ln–N bond products formulated as CyNC{[N,N-(2,5-Me2C4H2N)CH2CH2]2N}NCyLn[N(SiMe3)2]2 (Ln = La (4), Nd (5)). Reactions of the lanthanide amides with Me3SiCN were also examined. A mixed reaction of [(Me3Si)2N]3La(μ-Cl)Li(THF)3, [(2,5-Me2C4H2N)CH2CH2]2NH (1), and Me3SiCN in toluene at room temperature produced the novel cyano bridged dinuclear lanthanum complex η5:η1:η3-[(2,5- Me2C4H2NCH2CH2)2N]La[N(SiMe3)2](μ-CN)La[N(SiMe3)2]3 (6). The stoichiometric reactions of lanthanide amides 2 or 3 with Me3SiCN produced the novel trinuclear lanthanum and neodymium complexes {(η5:η1-[(2,5-Me2C4H2NCH2CH2)2N]Ln[N(SiMe3)2](μ-CN)}3 (Ln = La (7), Nd (8)) through selective σ-bond metathesis reaction of the terminal Ln–N (N(SiMe3)2) bond with the Si–C bond of Me3SiCN. On the basis of the stoichiometric reactions of complexes 2, or 3 with Me3SiCN, complexes 2, 3, 4, 5, 7, and 8 as catalysts for cyanosilylation of ketones were investigated. Results indicated that these complexes displayed a high catalytic activity on addition of Me3SiCN to ketones, and the activity of the complexes has the order of 7 ∼ 8 > 2 ∼ 3 ∼ 4 ∼ 5. Thus, complex 7 or 8 was proposed as the active catalyst in the catalytic reaction for the precatalysts of 2 and 3.

Asymmetric synthesis of the C(6–18) bis(tetrahydropyran)spiroacetal fragment of the lituarines

We describe efforts to achieve a multigram synthesis of the tricyclic spiroacetal core of the lituarines based on the addition of acyl anion equivalent to 4-(2-furyl)butan-2-one ( 18). We report the first cases of chemoselective Achmatowicz reaction in the presence of a second furan ring that lacks an α-hydroxyl group. The use of lithiated methoxyallene provides an efficient one-step conversion of ketone 18 into a tricyclic Diels–Alder adduct ( 27). In the final route, asymmetric cyanosilylation of ketone 29 achieved the construction of the stereogenic C(12) 3°-alcohol centre. Subsequent butenylation, diastereoselective reduction of keto-alcohol (+)- 33 and alkene cross metathesis set up an oxy-Michael reaction to close the C(8–12) tetrahydropyran ring. The second ring-closure, which completed the route, was achieved by oxidative spirocyclisation following our earlier work.

ChemInform Abstract: Asymmetric Cyanosilylation of Ketones Catalyzed by Recyclable Polymer‐Supported Copper(II) Salen Complexes.

AbstractThe application of soluble and insoluble polymer‐supported Cu(salen) complexes as catalysts in asymmetric cyanosilylation reactions is reported.

Asymmetric cyanosilylation of ketones catalyzed by recyclable polymer-supported copper(II) salen complexes

Various ketones have undergone asymmetric trimethylsilylcyanation at room temperature with (CH 3) 3SiCN (TMSCN) in the presence of a chiral-supported Cu(salen) complex and Ph 3PO as the catalyst. Aromatic, aliphatic, and heterocyclic ketones have been converted into the corresponding cyanohydrin trimethylsilyl ethers in 83−96% yields with 52−84% ee. Several factors concerning the reactivity and enantioselectivity have been discussed. A double activation where Cu(salen) plays the role of Lewis acid and Ph 3PO acts as a Lewis base is reported. Poly(ethylene glycol) monomethyl ether (MeO-PEG) has been used as a soluble support while Janda Jel (JJ) and Merrifield (MF) resins served as insoluble supports. Each polymer is linked to the salen catalyst through a glutarate spacer. The soluble catalysts were recovered by precipitation with a suitable solvent while the insoluble catalysts were simply filtered from the reaction mixture. The Janda Jel-attached Cu(salen) catalyst could be used for five cycles with the retention of efficiency and the Merrifield-bound Cu(salen) catalyst was found to loose activity with each use.

Understanding the role of the bifunctional titanium catalyst in cyanosilylation of ketones: A computational study

The molecular mechanism of the reaction of 2-heptanone and trimethylsilyl cyanide (TMSCN) catalyzed by the bifunctional titanium catalyst (to produce cyanohydrin) has been investigated using density functional theory calculations. With the bifunctional titanium catalyst, the reaction is likely to proceed through the following steps sequentially: (1) the isomerization of the cyano group into the isocyano group at the Si center of TMSCN; (2) the addition of the isocyano group to the ketone; (3) the silylation of the cyanoalkoxyl group to give the product. Our calculations reveal that the phosphine oxide group (as the Lewis base) and the titanium atom (as the Lewis acid) in the catalyst work cooperatively to promote the nucleophilic addition of the isocyano group to the ketone, and the silylation of the resulting cyanoalkoxyl group to form the product, respectively.

ChemInform Abstract: Chiral Lithium Salts of Phosphoric Acids as Lewis Acid—Base Conjugate Catalysts for the Enantioselective Cyanosilylation of Ketones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Chiral Lithium Salts of Phosphoric Acids as Lewis Acid–Base Conjugate Catalysts for the Enantioselective Cyanosilylation of Ketones

AbstractThe catalytic enantioselective cyanosilylation of aromatic ketones was developed by using chiral lithium salts of (R)‐BINOL‐ or (S)‐BINAM‐derived phosphoric acid compounds. In the presence of 10 mol% of chiral conjugate lithium salts, the corresponding tertiary cyanohydrins were obtained in high yields with moderate to high enantioselectivities. This is the first efficient example of asymmetric catalysis using lithium salts of synthetically useful chiral phosphoric acid compounds. A possible catalytic mechanism and transition states are also discussed as a preliminary working hypothesis.

ChemInform Abstract: Discrete verus in situ‐Generated Aluminum‐Salen Catalysts in Enantioselective Cyanosilylation of Ketones: Role of Achiral Ligands.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Enantioselective cyanosilylation of ketones catalyzed by recyclable polymeric and dimeric MN(III) salen complexes at room temperature

Recyclable polymeric 1 and dimeric 2 chiral Mn(III) salen complexes catalyzed enantioselective cyanosilylation of various ketones in the presence of triphenylphosphine oxide as an additive proceeded smoothly at room temperature, providing excellent yields (up to 98%) and enantiomeric excess (up to 86%) of respective cyanohydrin trimethylsilyl ether. For most of the substrates, the Catalyst 1 showed slightly better reactivity and enantioselecitivity than the Catalyst 2 nevertheless both the catalysts were easily recovered and reused four times with the retention of their efficiency.

ChemInform Abstract: Highly Enantioselective Cyanosilylation of Ketones Catalyzed by a Bifunctional Ti(IV) Complex.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Discrete versus In Situ‐Generated Aluminum‐Salen Catalysts in Enantioselective Cyanosilylation of Ketones: Role of Achiral Ligands

AbstractThe monometallic species {Salen}AlX (X=Me, 2a,b; X=Cl, 4a,b; O‐i‐Pr, 5a,b) and open bimetallic species {Salen}[AlMe2]2 (3a,b) that result from binary combinations between an aluminum precursor [trimethylaluminum, dimethylaluminum chloride, aluminum tris(isopropoxide)] and a diprotio {Salen}H2 pro‐ligand 1a,b (a=1R,2R‐cyclohexyl‐salen; b=1R,2R‐diphenylethylene‐salen) have been isolated. The crystal structures of 3b, 4b and of μ‐oxo species [{diphenylethylene‐salen}Al]2O (6b) are reported. The discrete species 2–5a,b have been individually evaluated in the asymmetric cyanosilylation of acetophenone. It is shown that, in several cases, these discrete catalysts display dramatically different performances than the catalyst systems in situ‐generated from the binary combinations. The influence of the achiral ligand X on both the enantioselectivity and activity of the cyanosilylation reaction has been investigated, resulting in the definition of a highly active and productive hexafluoro‐2‐propoxide‐based catalyst for a variety of aryl alkyl ketones (TON up to 470, TOF up to 140 h−1 at −20 °C for acetophenone).