Catalytic asymmetric synthesis of O-acetyl cyanohydrins from KCN, Ac2O and aldehydes

Belokoń, Yuri N.; Gutnov, Andrey; Москаленко, М. А.; Yashkina, L. V.; Lesovoy, Denis E.; Ikonnikov, N. S.; Larichev, Vladimir; North, Michael

doi:10.1039/b110335k

Cited by 74 publications

(27 citation statements)

References 8 publications

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“…This paper reports the asymmetric synthesis of O-acetylcyanohydrins by the reaction of KCN, acetic anhydride (Ac 2 O), and aldehydes catalyzed by complexes 1 (Scheme 1) and the analogously built V IV and V V complexes (R)-2 and (R)-3, respectively. A preliminary report of some of these results was published earlier [6].…”

mentioning

confidence: 94%

Catalytic Asymmetric Synthesis of O-Acetylcyanohydrins from Potassium Cyanide, Acetic Anhydride, and Aldehydes, Promoted by Chiral Salen Complexes of Titanium(IV) and Vanadium(V)

Belokoń

Carta

Gutnov

et al. 2002

HCA

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108

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Dedicated to Professor Dieter Seebach on the occasion of his 65th birthdayThe utility of the chiral [Ti(m-O)(salen)] 2 complexes (R)-and (S)-1 (H 2 salen was prepared from (R,R)-or (S,S)-cyclohexane-1,2-diamine and 3,5-di(tert-butyl)-2-hydroxybenzaldehyde) as catalysts for the asymmetric addition of KCN and Ac 2 O to aldehydes to produce O-acetylcyanohydrins was investigated. It was shown that the complexes were active at a substrate/catalyst ratio of 100 : 1 and produced the O-protected cyanohydrins with ee in the range of 60 ± 92% at À 408. Other complexes, [Ti 2 (AcO) 2 (m-O)(salen) 2 ] ((R)-4) and [Ti(CF 3 COO) 2 (salen)] ((R)-5), were prepared from (R)-1 by treatment with different amounts of Ac 2 O and (CF 3 CO) 2 O, and their catalytic activities were tested under the same conditions. The efficiency of (R)-4 was found to be even greater than that of (R)-1, whereas (R)-5 was inactive. The synthesis of the corresponding salen complexes of V IV and V V ,, was elaborated, and their X-ray crystal structures were determined. The efficiency of (R)-3 was sufficient to produce O-acetyl derivatives of aromatic cyanohydrins with ee in the range of 80 ± 91% at À 408.Introduction. ± As enantiomerically pure cyanohydrins are versatile intermediates in organic synthesis, many synthetic approaches to their syntheses are being vigorously pursued [1]. The catalytic ways of making this class of compounds rely upon the asymmetric addition of a cyanide source to the carbonyl group of aldehydes, as catalyzed by enzymes [2] or purely chemical chiral catalysts [3]. Enantiomerically enriched O-protected cyanohydrins are customarily made by the reaction of aldehydes with Me 3 SiCN usually catalyzed by chiral Lewis acids [1]. We recently reported an efficient catalysis of this reaction by the chiral binuclear [Ti IV (salen)] complex 1 (Fig. 1), active at a ratio of substrate/catalyst as high as 1000 : 1 and promoting the addition at room temperature with ee in the range of 80 ± 92% [4]. Very efficient catalysts based on bifunctional complexes of Al III and Ti IV have also been developed by Shibasaki and co-workers, giving O-(trimethylsilyl) derivatives of cyanohydrins with ee as high as 90 ± 99% at À 428 [5].Unfortunately, Me 3 SiCN is an expensive material, and HCN is extremely toxic. Evidently, there is a need to find cheaper and safer initial materials for the synthesis of enantiomerically pure O-protected cyanohydrins. This paper reports the asymmetric synthesis of O-acetylcyanohydrins by the reaction of KCN, acetic anhydride (Ac 2 O),

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confidence: 94%

Catalytic Asymmetric Synthesis of O-Acetylcyanohydrins from Potassium Cyanide, Acetic Anhydride, and Aldehydes, Promoted by Chiral Salen Complexes of Titanium(IV) and Vanadium(V)

Belokoń

Carta

Gutnov

et al. 2002

HCA

Self Cite

108

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“…[7] A more convenient one-pot procedure which, however, required large excess of reagents, was described, whereby enantioselective cyanation of aldehydes using KCN was performed in the presence of acetic anhydride. [8] Another one-pot procedure based on dynamic kinetic resolution of in situ obtained racemic cyanohydrins using lipase B from Candida antarctica in the presence of an acylating agent, led to slow formation of enantioenriched cyanohydrin esters. [9] Procedures for direct additions of a-ketonitriles to prochiral aldehydes, avoiding the formation of accompanying products, are attractive due to their simplicity and atom economy.…”

Section: Introductionmentioning

confidence: 99%

Lewis Acid–Lewis Base‐Catalysed Enantioselective Addition of α‐Ketonitriles to Aldehydes

Lundgren¹,

Wingstrand²,

Moberg³

2007

Adv Synth Catal

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Additions of structurally diverse a-ketonitriles to aromatic and aliphatic prochiral aldehydes yielding highly enantioenriched acylated cyanohydrins were achieved using a combination of a titanium salen dimer and an achiral or chiral Lewis base. In most cases high yields and high enantioselectivities were observed. The ee was moderate in the initial part of the reaction but increased over time. This could be avoided, and higher ees obtained, by keeping the titanium complex, in the presence or absence of aldehyde and ketonitrile, at À40 8C prior to the addition of the Lewis base. A mechanism initiated by nucleophilic attack of the tertiary amine at the carbonyl carbon atom of the ketonitile is supported by 13 C labelling experiments.

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“…We also extended this cyanoformylation protocol to these substrates using monomeric V(V) salen complex 2 as catalyst which showed comparable yields and enantioselectivities. However, the reaction took longer time when compared with the use of polymeric V(V) salen complex 1 as catalyst (Table 2, Entries 2, 4,6,8,10,12,14,16,18,22,24,26,28,30,32). Moreover, in the case of monomeric complex 2, the catalyst was not recoverable though the hydrotalcite was recovered and recycled at the end of the catalytic run, whereas in the case of polymeric catalyst both catalyst and hydrotalcite were recoverable and recyclable.…”

Section: Typical Experimental Procedures For the Enantioselective Cyanmentioning

confidence: 71%

Enantioselective cyanoformylation of aldehydes catalyzed with solid base mediated chiral V(V) salen complexes

et al. 2009

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Polymeric and monomeric V(V) chiral salen complexes-catalyzed enantioselective ethyl cyanoformylation of aldehydes using ethyl cyanoformate as a source of cyanide was accomplished in the presence of several basic cocatalysts viz., NaOH, KOH, basic Al2O3 and hydrotalcite. Excellent yield (>95%) of chiral ethyl cyanohydrincarbonate with high enantioselectivity up to 94% was achieved in 24-36 h when hydrotalcite was used as an additive. The polymeric catalyst 1 is more reactive than the monomeric catalyst 2 to produce chiral ethyl cyanohydrincarbonate in high optical purity. The chiral polymeric catalyst 1 and cocatalysts hydrotalcite and basic alumina used in this study were recoverable and recyclable several times with retention of its performance.

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Catalytic asymmetric synthesis of O-acetyl cyanohydrins from KCN, Ac2O and aldehydes

Cited by 74 publications

References 8 publications

Catalytic Asymmetric Synthesis of O-Acetylcyanohydrins from Potassium Cyanide, Acetic Anhydride, and Aldehydes, Promoted by Chiral Salen Complexes of Titanium(IV) and Vanadium(V)

Catalytic Asymmetric Synthesis of O-Acetylcyanohydrins from Potassium Cyanide, Acetic Anhydride, and Aldehydes, Promoted by Chiral Salen Complexes of Titanium(IV) and Vanadium(V)

Lewis Acid–Lewis Base‐Catalysed Enantioselective Addition of α‐Ketonitriles to Aldehydes

Enantioselective cyanoformylation of aldehydes catalyzed with solid base mediated chiral V(V) salen complexes

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