On the origin of π-facial diastereoselectivity in nucleophilic additions to chiral carbonyl compounds. 1. Rotational profiles of propionaldehyde 1, chloroacetaldehyde 2, and 2-chloropropionaldehyde 3.

Frenking, Gernot; Köhler, Klaus; Reetz, Manfred T.

doi:10.1016/s0040-4020(01)86504-2

Cited by 33 publications

(19 citation statements)

References 33 publications

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“…The axial and diaxial isomers have greater calculated stabilities than the mono and diequatorial derivatives of 1. The calculated difference between axial 6 and equatorial 2 is 1.7 kcallmol, which agrees well with that recently calculated for the two rotamers of 2-chloropropionaldehyde, which have almost identical stereochemistry (16). The difference in stability was attributed mainly to a difference in the dipolar interactions as previously seen for 2-chlorocyclohexanone (17).…”

Section: Molecl~lar Mechanics Calculations Using MMXsupporting

confidence: 90%

An X-ray and conformational study of the α-chloro derivatives of 5,7-dihydro-1,11-dimethyl-6H-dibenzo[a,c]cyclohepten-6-one

Fraser¹,

Bensimon²,

Faibish³

et al. 1994

Can. J. Chem.

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. The crystal structures for four a-chloro derivatives 2-5 of the titled ketone 1 have been determined, confirming their earlier assignments of stereochemistry. Variations in the conformations of 2-5 suggested some flexibility in the central seven-membered ring. Molecular mechanics calculations of the changes in energy as a function of the internal torsional angles at the carbonyl of these chloro derivatives indicated the ring flexibility to be comparable to that of cyclohexanone. In the three compounds containing an axial chlorine the distance between the chlorine atom and two of the carbon atoms of the more remote benzene ring was 3.2 + 0.1 A, suggesting the value for the thickness of a benzene ring may be significantly smaller than the accepted value when it is interacting with a single atom.ROBERT R. FRASER, CORINNE BENSIMON, NEIL C. FAIBISH et FANZUO KONG. Can. J. Chem. 72, 148 1 (1994). On a dCterminC les structures cristallines des quatre dCrivCs a-chlorks 2-5 de la cCtone 1 mentionnCe dans le titre et on a ainsi confirm6 les attributions de stCrCochimie faites antCrieurement. Les variations dans les structures des composCs 2-5 suggkrent l'existence d'une certaine flexibilitk dans le cycle central B sept chainons. Des calculs de mCcanique molCculaire des changements d'Cnergie en fonctions des angles de torsion internes au niveau du carbonyle de ces dCrivCs chlorCs indiquent que la flexibilitC du cycle est comparable B celle de la cyclohexanone. Dans les trois composCs contenant un atome de chlode axial, la distance entre l'atome de chlore et deux des atomes de carbone du noyau benzCnique le plus Cloignt est de 3,2 + 0, I A; ceci suggbre que la valeur pour 1'Cpaisseur d'un noyau benzCnique interagissant avec un seul atome est peut-&tre beaucoup plus faible que la valeur gCnCralement acceptCe.[Traduit par la RCdaction]The bridged biaryl ketone, 5.7-dihydro-1, 11-dimethyl-6H- through its central ring giving rise to two possible orientations a to the carbonyl, either "axial" or "equatorial" on the basis of their similarity to the geometry at the a positions of cyclohexanone (see Fig. 1). The ring was considered by Mislow to possess a single rigid conformation as indicated by molecular models and supported by its proton nrnr spectra (2). We have used this ketone in a variety of studies involving the effects of stereochemistry on reactivity since it offered certain advantages over cyclohexanone as a model. One example involves a study of the hydrogen-deuterium exchange reaction for the axial and equatorial protons a to the carbonyl (3). In another, measurement of the variation in rates of addition of nucleophiles to 1 as a function of the stereochemistry of its a methyl and chloro derivatives provided evidence for the primary importance of torsional interactions as contributors to the antiperiplanar effect (4). The validity of the assumption of rigidity of 1, and thus its ability as a model to provide derivatives of known fixed stereochemistry, was examined for 3 and its methyl derivatives using X-ray crystallo...

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Section: Molecl~lar Mechanics Calculations Using MMXsupporting

confidence: 90%

An X-ray and conformational study of the α-chloro derivatives of 5,7-dihydro-1,11-dimethyl-6H-dibenzo[a,c]cyclohepten-6-one

Fraser¹,

Bensimon²,

Faibish³

et al. 1994

Can. J. Chem.

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“…The importance of CH 3 ⋅⋅⋅O hydrogen bonds has been suggested in the structures of the transition states for the nucleophilic reactions of propanal (Scheme 5 c and g),23, 25a 2‐ fluoropropanal (Scheme 5 d–f),24 2‐chloropropanal, 2‐methoxypropanal (Scheme 5 h and i),25 2‐ N , N ‐dimethylpropanal, 2‐silylpropanal, and 2‐trimethylsilylpropanal (Scheme 5 j) 26…”

Section: Resultsmentioning

confidence: 99%

Origin of the π‐Facial Stereoselectivity in the Addition of Nucleophilic Reagents to Chiral Aliphatic Ketones as Evidenced by High‐Level Ab Initio Molecular‐Orbital Calculations

Takahashi

Yamasaki

Kohno

et al. 2006

Chemistry An Asian Journal

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Ab initio molecular-orbital (MO) calculations were carried out, at the MP2/6-311++G(d,p)//MP2/6-31G(d) level, to investigate the conformational Gibbs energy of alkyl 1-cyclohexylethyl ketones, cyclo-C6H11CHCH3-CO-R (R = Me, Et, iPr, and tBu). In each case, one of the equatorial conformations was shown to be the most stable. Conformers with the axial CHCH3COR group were also shown to be present in an appreciable concentration. Short C-H...C=O and C-H...O=C distances were found in each stable conformation. The result was interpreted on the grounds of C-H...pi(C=O) and C-H...O hydrogen bonds, which stabilize the geometry of the molecule. The ratio of the diastereomeric secondary alcohols produced in the nucleophilic addition to cyclo-C6H11CHCH3-CO-R was estimated on the basis of the conformer distribution. The calculated result was consistent with the experimental data previously reported: the gradual increase in the product ratio (major/minor) along the series was followed by a drop at R = tBu. The energy of the diastereomeric transition states in the addition of LiH to cyclo-C6H11CHCH3-CO-R was also calculated for R = Me and tBu. The product ratio did not differ significantly in going from R = Me to tBu in the case of the aliphatic ketones. This is compatible with the above result calculated on the basis of the conformer distribution. Thus, the mechanism of the pi-facial selection can be explained in terms of the simple premise that the geometry of the transition state resembles the ground-state conformation of the substrates and that the nucleophilic reagent approaches from the less-hindered side of the carbonyl pi face.

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“…A few quantum chemical calculations were also performed13–16 on different conformers of Pr for varying values of the dihedral angle defining the torsion of the aldehydic group. Almost a decade ago, Kolandaivel et al 17 reported the molecular structure and conformational stability of the E and Z geometrical isomers of propionaldehyde oxime by using the ab initio and density functional theory (DFT) methods.…”

Section: Introductionmentioning

confidence: 99%

Self‐association and hydrogen bonding of propionaldehyde in binary mixtures with water and methanol investigated by concentration‐dependent polarized Raman study and DFT calculations

Singh

Srivastava

Schlücker

et al. 2010

J Raman Spectroscopy

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The Raman spectra of neat propionaldehyde [CH 3 CH 2 CHO or propanal (Pr)] and its binary mixtures with hydrogen-donor solvents, water (W) and methanol (M), [CH 3 CH 2 CHO + H 2 O]and CH 3 CH 2 CHO + CH 3 OH] with different mole fractions of the reference system, Pr varying from 0.1 to 0.9 at a regular interval of 0.1, were recorded in the ν(C O) stretching region, 1600-1800 cm −1 . The isotropic parts of the Raman spectra were analyzed for both the cases. The wavenumber positions and line widths of the component bands were determined by a rigorous line-shape analysis, and the peaks corresponding to self-associated and hydrogen-bonded species were identified. Raman peak at ∼1721 cm −1 in neat Pr, which has been attributed to the self-associated species, downshifts slightly (∼1 cm −1 ) in going from mole fraction 0.9 to 0.6 in (Pr + W) binary mixture, but on further dilution it shows a sudden downshift of ∼7 cm −1 . This has been attributed to the low solubility of Pr in W (∼30%), which does not permit a hydrogen-bonded network to form at higher concentrations of Pr. A significant decrease in the intensity of this peak in the Raman spectra of Pr in a nonpolar solvent, n-heptane, at high dilution (C = 0.05) further confirms that this peak corresponds to the self-associated species. In case of the (Pr + M) binary mixture, however, the spectral changes with concentration show a rather regular trend and no special features were observed.

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On the origin of π-facial diastereoselectivity in nucleophilic additions to chiral carbonyl compounds. 1. Rotational profiles of propionaldehyde 1, chloroacetaldehyde 2, and 2-chloropropionaldehyde 3.

Cited by 33 publications

References 33 publications

An X-ray and conformational study of the α-chloro derivatives of 5,7-dihydro-1,11-dimethyl-6H-dibenzo[a,c]cyclohepten-6-one

An X-ray and conformational study of the α-chloro derivatives of 5,7-dihydro-1,11-dimethyl-6H-dibenzo[a,c]cyclohepten-6-one

Origin of the π‐Facial Stereoselectivity in the Addition of Nucleophilic Reagents to Chiral Aliphatic Ketones as Evidenced by High‐Level Ab Initio Molecular‐Orbital Calculations

Self‐association and hydrogen bonding of propionaldehyde in binary mixtures with water and methanol investigated by concentration‐dependent polarized Raman study and DFT calculations

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