Chelates as intermediates in nucleophilic additions to alkoxy ketones according to Cram's rule (cyclic model)

Chen, Xiangning; Hortelano, Edwin R.; Eliel, Ernest L.; Frye, Stephen V.

doi:10.1021/ja00031a036

Cited by 170 publications

(131 citation statements)

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“…R1 corresponds with the addition of ( ) CH MgCl to 2-hydroxypropanal while R2 is associated with the reaction of CH Mg plus Cl Mg and 2-hydroxypropanal. 3 …”

Section: ý ýmentioning

confidence: 97%

“…ture of CH MgCl, CH Mg, and Cl Mg, all of 3 3 2 2 which can react with chiral ␣-alkoxy carbonyl compounds, we have considered the addition with Ž . CH Mg q Cl Mg.…”

Section: ý ýmentioning

confidence: 99%

“…In the case of the addition of two equivalents of CH MgCl to the carbonyl group of the 2-hydroxy- 3 propanal, the barrier heights are predicted to be Ž lower than in the 1:1 stoichiometry case 3᎐9 . kcalrmol , the anti attack on the anti chelate being the most favorable pathway.…”

mentioning

confidence: 95%

“…more powerful quelant agent than is the CH Mg system. Therefore, the reaction 3 2 pathway associated to the nucleophilic attack of CH MgCl q 2-hydroxypropanal presents 3 …”

mentioning

confidence: 99%

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Understanding the mechanism of the addition of organomagnesium reagents to 2-hydroxypropanal: An ab initio molecular orbital analysis

Oliva¹,

Safont²,

Andrés³

et al. 1997

Int. J. Quant. Chem.

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ABSTRACT:The molecular mechanism for the gas-phase addition of Ž . Ž . organomagnesium reagents: CH MgCl, 2CH MgCl, CH Mg, and CH Mg plus Cl Mg, to 2-hydroxypropanal as a model of chiral ␣-alkoxy carbonyl compounds is 2 investigated at the 6-31G* basis-set level of calculation. An extensive exploration of the reactive potential energy surface was carried out in order to locate and characterize the stationary points. The geometry of stationary points and the harmonic vibrational frequencies, transition vectors, and electronic structure of the transition structures were obtained. The theoretical results are analyzed, discussed, and compared with previous theoretical and available experimental data. The first step corresponds to the exothermic formation of the chelate complexes without an energy barrier. These stationary points correspond to puckered five-membered rings, determining the stereochemistry of the global process, which is retained throughout the reaction pathway. For the reactions of w Ž . x one equivalent of an organomagnesium compound CH MgCl or CH Mg , the second 3 3 2 step for the intramolecular mechanism is associated to the C-C bond formation via 1,3-migration of the nucleophilic methyl group from the organomagnesium compound to the carbonyl carbon and the corresponding transition structure can be described as a four-membered ring, the anti attack being the most favorable pathway. CH MgCl is a 3 Ž . more powerful quelant agent than is the CH Mg system. Therefore, the reaction Cl Mg systems yields an intermolecular mechanism, the barrier height decreases, and 2Correspondence to: M. Oliva.

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“…R1 corresponds with the addition of ( ) CH MgCl to 2-hydroxypropanal while R2 is associated with the reaction of CH Mg plus Cl Mg and 2-hydroxypropanal. 3 …”

Section: ý ýmentioning

confidence: 97%

“…ture of CH MgCl, CH Mg, and Cl Mg, all of 3 3 2 2 which can react with chiral ␣-alkoxy carbonyl compounds, we have considered the addition with Ž . CH Mg q Cl Mg.…”

Section: ý ýmentioning

confidence: 99%

mentioning

confidence: 95%

“…more powerful quelant agent than is the CH Mg system. Therefore, the reaction 3 2 pathway associated to the nucleophilic attack of CH MgCl q 2-hydroxypropanal presents 3 …”

mentioning

confidence: 99%

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Understanding the mechanism of the addition of organomagnesium reagents to 2-hydroxypropanal: An ab initio molecular orbital analysis

Oliva¹,

Safont²,

Andrés³

et al. 1997

Int. J. Quant. Chem.

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“…It is well known that coexisting metal halides, such as lithium chloride and magnesium bromide, play an important role in the stereochemical outcome of the nucleophilic addition of an organometallic to α-and β-oxycarbonyl compounds through cyclic chelation models. 21, 22 The results have been rationalized in terms of the chelation mechanism by lithium, an alkali metal, and magnesium, an alkaline earth metal.…”

mentioning

confidence: 99%

Studies on High-energy Collision-induced Dissociation of Endogenous Cannabinoids: 2-Arachidonoylglycerol and N-Arachidonoylethanolamide in FAB–Mass Spectrometry

2006

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Both 2-AG (1) and anandamide (2) exhibit cannabimimetic activities and act as endogenous ligands for cannabinoid receptors in various mammalian tissues. 1 2-AG is known to be an intrinsic natural ligand for the cannabinoid receptors, while anandamide was shown to be a weak partial agonist. 2,3 MS is an important technique for analyzing these endogenous ligands. Gas chromatography-MS (GC-MS) 4,5 and liquid chromatography-MS (LC-MS) 6,7 have been used as methods for detecting these compounds.FAB ionization is applicable in LC-FAB-MS(/MS) systems, and has been widely used to identify biologically active compounds, e.g., dinucleotide, 8 acetylcholine, 9 and dextromethorphan, 10 or natural products, e.g., cytokinin 11 and oligosaccharide derivative. 12The FAB-MS/MS technique was applied in the characterization of naturally occurring compounds, e.g., terpene or glycoside 13 and phenolic constituents. 14 High-energy collision activation of ions that contain a stable charge-site results in decompositions that occur remote from the site of charge, i.e., CRF, and has been shown to provide a technique for determining the positions of double bonds, branch points, and other functional groups in a large variety of biological and other molecules. 15,16 A stable charge-site is either anionic, as in carboxylate, sulfate, and sulfonate anions, or cationic, as in protonated quaternary amines, sulfonium, and phosphonium cations, as well as in molecules that have been cationized with metal ions. CRF by CID-MS/MS has been used for determining the double-bond positions in long alkenyl chains, e.g., polyhydroxypolyene 17 from marine sources, and alkenylresorcinol, 18 or alkenylsalicylic acid 19 from natural plants. In our previous study, 20 analyses of anandamide (2) and endocannabinoid-like compounds using high-energy CID-MS/MS in FAB-MS were performed. The CID-MS/MS spectra of lithium-adduct [M+Li] + ions were rich in structurally informative CRF patterns, which provided information on the locations of double bonds in the hydrocarbon chain, which is useful for determining the structure.As a part of research work relating to the high-energy CID-MS/MS reactions of endogenous cannabinoids and several endocannabinoid-like compounds, in the present paper we describe the optimal measurement conditions for the analysis of 2-AG (1) using the CID-MS/MS technique in FAB-MS, focusing on adduct metals, i.e., alkali metals (group 1 elements) and alkaline earth metals (group 2 elements), and matrices. The ability of alkali and alkaline earth metal cations to form a stable charge-site to provide structurally informative CRF ions in the CID-MS/MS measurement is examined. Since 2-AG contains a 1,3-dihydroxyl moiety, the formation of cyclic β-chelation between 2-AG and alkaline earth metal could be expected to give the tightly localized charge-site necessary for CRF. It is well known that coexisting metal halides, such as lithium chloride and magnesium bromide, play an important role in the stereochemical outcome of the nucleophilic addition of an o...

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Asymmetrized Tris(hydroxymethyl)methane and Related Synthons: Enantioselective Preparation and Synthetic Applications

Banfi¹,

Guanti²

1998

Eur. J. Org. Chem.

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Asymmetrized tris(hydroxymethyl)methane (THYM*) is a new chiral building block easily accessible in both enantiomeric forms by a chemoenzymatic methodology. The presence of three synthetically equivalent masked hydroxymethyl groups and a high degree of latent symmetry (C3v) makes this synthon very versatile in synthetic applications. This review describes its preparation and a series of elaborations (with particular enphasis on the diastereoselective generation of additional chiral centers) leading to advanced intermediated for the preparation of biologically active compounds.

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Chelates as intermediates in nucleophilic additions to alkoxy ketones according to Cram's rule (cyclic model)

Cited by 170 publications

References 2 publications

Understanding the mechanism of the addition of organomagnesium reagents to 2-hydroxypropanal: An ab initio molecular orbital analysis

Understanding the mechanism of the addition of organomagnesium reagents to 2-hydroxypropanal: An ab initio molecular orbital analysis

Studies on High-energy Collision-induced Dissociation of Endogenous Cannabinoids: 2-Arachidonoylglycerol and N-Arachidonoylethanolamide in FAB–Mass Spectrometry

Asymmetrized Tris(hydroxymethyl)methane and Related Synthons: Enantioselective Preparation and Synthetic Applications

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