Bio-organic synthesis of optically active cyanohydrins and acyloins

Brussee, Johannes; Roos, Eric C.; Gen, A. Van Der

doi:10.1016/s0040-4039(00)80529-8

Cited by 109 publications

(26 citation statements)

References 14 publications

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“…Spectroscopic data of the product were identical to that previously reported in the literature [14]. The absolute configuration was assigned by means of optical rotation [15]. Crystals of 1-Zr(O t Bu) 2 were prepared as follows: Zr(O t Bu) 4 (25 lL, 0.064 mmol) was added to a suspension of ligand 1 (22.5 mg, 0.054 mmol) in dry benzene (0.5 mL) at 70°C under an Ar atmosphere.…”

Section: 3supporting

confidence: 75%

Chiral bispyridylamide metal complexes as catalysts for the enantioselective addition of TMSCN to aldehydes

Belda

Duquesne

Fischer³

et al. 2004

Journal of Organometallic Chemistry

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Section: 3supporting

confidence: 75%

Chiral bispyridylamide metal complexes as catalysts for the enantioselective addition of TMSCN to aldehydes

Belda

Duquesne

Fischer³

et al. 2004

Journal of Organometallic Chemistry

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“…[b] Determined by chiral GC analysis of the cyanohydrin acetate unless stated otherwise. [c] Determined by comparison of the specific rotation with literature data 27. [d] Determined by 1 H NMR spectroscopy in the presence of ( R )‐mandelic acid and dimethylaminopyridine (DMAP).…”

Section: Resultsmentioning

confidence: 99%

“…The enantiomeric excesses of the cyanohydrin trimethylsilyl ethers were again found to always be > 50 %, [23] confirming that the reaction being monitored was the catalysed rather than uncatalysed reaction. [27] [d] Determined by 1 H NMR spectroscopy in the presence of (R)-mandelic acid and dimethylaminopyridine (DMAP). Table 1.…”

Section: Resultsmentioning

confidence: 99%

“…Table 4 presents the kinetic data obtained for the asymmetric trimethylsilylcyanation of fifteen aldehydes by using 2 mol % of the aluminiumbased catalyst 5 and 10 mol % of triphenylphosphine oxide as catalysts. These reactions all obeyed first-order kinetics, [23] [27] [d] Determined by 1 H NMR spectroscopy in the presence of (R)-mandelic acid and DMAP. Table 3.…”

Section: Resultsmentioning

confidence: 99%

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Investigation of Lewis Acid versus Lewis Base Catalysis in Asymmetric Cyanohydrin Synthesis

North

Omedes-Pujol

Williamson

2010

Chemistry A European J

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The asymmetric addition of trimethylsilyl cyanide to aldehydes can be catalysed by Lewis acids and/or Lewis bases, which activate the aldehyde and trimethylsilyl cyanide, respectively. It is not always apparent from the structure of the catalyst whether Lewis acid or Lewis base catalysis predominates. To investigate this in the context of using salen complexes of titanium, vanadium and aluminium as catalysts, a Hammett analysis of asymmetric cyanohydrin synthesis was undertaken. When Lewis acid catalysis is dominant, a significantly positive reaction constant is observed, whereas reactions dominated by Lewis base catalysis give much smaller reaction constants. [{Ti(salen)O}(2)] was found to show the highest degree of Lewis acid catalysis, whereas two [VO(salen)X] (X=EtOSO(3) or NCS) complexes both displayed lower degrees of Lewis acid catalysis. In the case of reactions catalysed by [{Al(salen)}(2)O] and triphenylphosphine oxide, a non-linear Hammett plot was observed, which is indicative of a change in mechanism with increasing Lewis base catalysis as the carbonyl compound becomes more electron-deficient. These results suggested that the aluminium complex/triphenylphosphine oxide catalyst system should also catalyse the asymmetric addition of trimethylsilyl cyanide to ketones and this was found to be the case.

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“…The absolute config uration was determined by a comparison of the sign of the op tical rotation angle of the obtained product with the litera ture data. 16 This work was financially supported by the Russian …”

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confidence: 99%

Lithium salts of chiral metallocomplex anions as catalysts for asymmetric trimethylsilylcyanation of aldehydes

et al. 2010

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A series of the anionic Co III complexes based on optically active amino acids containing the lithium cation in the external sphere of the complex was synthesized. The synthesized com pounds were used as catalysts in the asymmetric addition of trimethylsilyl cyanide to aldehydes. The influence of the temperature, catalyst concentration, and modification of the chiral anion structure on the enantioselectivity of catalysis was studied.In vast majority of the cases, metal complexes with chirality in the cationic part are used in asymmetric catal ysis. 1 An alternative strategy, which involved the com pounds bearing the chiral anion responsible for stereodif ferentiation as catalysts, is very rare. 2 A specific feature of these catalytic systems is that the negative charge is delo calized inside rather bulky fragment and, hence, the charge of the outer sphere cation is compensated to a less extent. Therefore, the cation is a stronger Lewis acid than the same ion chelated by chiral ligands. Thus, even alkali metal cations can be "transformed" into efficient Lewis acids.Only several examples of asymmetric reactions catalyzed by the ion pairs [alkali metal cation] + [chiral anion] -were described. 3-7 A family of heterobimetallic cata lysts representing rare earth metal complexes with chiral binaphthol and alkali metal cations in the outer sphere of the complex has previously 3 been synthesized. They were used in the aldol reaction and the Michael asym metric addition. Binaphthol monolithium salt was used in the asymmetric trimethylsilylcyanation of aldehydes. 4The influence of water additives on the enantioselectivity of this reaction was studied. 5 The cyanosilylation of ketones in the presence of lithium salts of phosphoric ac ids based on binaphthol was studied. 6 3,3´ Dichlorobi naphthol dilithium salt was used in the asymmetric aldol reaction. 7 It is considered that among alkali metals the lithium cation possesses the highest Lewis acidity. 8 It was shown 9 that a solution of lithium salt of permethylated icosahe dral monocarbadodecaborate LiCB 11 Me 12 in benzene is an efficient catalyst for pericyclic reactions. It seems prac tically important to use LiCB 11 Me 12 as a catalyst of alk ene radical polymerization. 10 In the previous work, 11 we used the chiral anionic com plexes of Λ and Δ bis[N salicylidene (S) aminoacidato] cobaltates 12 with potassium, sodium, and silver cations as Lewis acids in the asymmetric trimethylsilylcyanation of aldehydes and in the Mukayama reaction. We assumed that the rate of benzaldehyde trimethylsilylcyanation should increase with stronger Lewis acids, viz., complexes containing the lithium ion in the outer sphere. Indeed, it turned out that the half conversion time of the addition of trimethylsilyl cyanide (TMSCN) to benzaldehyde (Scheme 1) catalyzed by the complex Li + [Δ 1] -(the struc ture of the complex is shown in Scheme 2) is 1.3 min and the enantioselectivity reaches 23%, whereas for the com plexes Na + [Δ 1] -and K + [Δ 1] -the half conversion peri od is 5 and 6 min, res...

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Bio-organic synthesis of optically active cyanohydrins and acyloins

Cited by 109 publications

References 14 publications

Chiral bispyridylamide metal complexes as catalysts for the enantioselective addition of TMSCN to aldehydes

Chiral bispyridylamide metal complexes as catalysts for the enantioselective addition of TMSCN to aldehydes

Investigation of Lewis Acid versus Lewis Base Catalysis in Asymmetric Cyanohydrin Synthesis

Lithium salts of chiral metallocomplex anions as catalysts for asymmetric trimethylsilylcyanation of aldehydes

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