Pyrolytic Cis Eliminations.

DePuy, Charles H.; King, Roy W.

doi:10.1021/cr60207a001

Cited by 423 publications

(174 citation statements)

References 88 publications

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“…A rho value of -0.66 measured for the pyrolysis of the 1-arylethylacetates at 327° (following o-"*" relationship) (85) and a rate acceleration by electronegatlvely substituted aryl esters (86) indicates a small degree of charge separation on the alpha-carbon. This Is in agreement with the \ / (9) \ R relative pyrolytic rates (3° > 2° > 1°) of substituted esters (83).…”

Section: H-c-c+supporting

confidence: 89%

“…This tran sition state is consistent with the observed first order kinetics, the large negative entropy of activation, the absence of induction periods and of any effect by free radical Inhibitors, and the identity of the product olefins formed (84). Isotope effects Indicate a large amount of carbon-hydrogen bond breaking in the transition state (83), whereas the rho value (0.3) for the 2-arylethylacetates at 377° Indicates a small amount of negative charge buildup on the beta-carbon atom (85). A rho value of -0.66 measured for the pyrolysis of the 1-arylethylacetates at 327° (following o-"*" relationship) (85) and a rate acceleration by electronegatlvely substituted aryl esters (86) indicates a small degree of charge separation on the alpha-carbon.…”

Section: H-c-c+supporting

confidence: 84%

“…Pyrolytlc eliminations have been extensively Investigated using four groups of compounds---esters, xanthates, amine oxides, halldes and to a lesser extent using vinyl ethers, amides, carbonates, sulfoxides and alcohols. The predominant sterlc course of this reaction has been shown to be els by a number of Investigators (83). The transition state In volves a cyclic Intermediate In which the beta-hydrogen Is abstracted by the carbonyl oxygen of the ester as the C-0 bond Is breaking and some double-bond character Is developing between the carbon atoms.…”

Section: H-c-c+mentioning

confidence: 99%

“…These are (a) the number of available hydrogen atoms on each adjacent carbon atom (statistical ef fect), (b) the repulsive interactions of groups in the transition state (steric effects), (c) the relative stability of the olefinic products formed (thermodynamic effects), and (d) the relative acidity of the hydro gen atom removed-this may become important in esters with especially activated hydrogen atoms (83).…”

Section: H-c-c+mentioning

confidence: 99%

“…Extensive work has been published on the pyrolyses of allcylic com pounds (38,83,89) and the more highly substituted olefin usually pre dominates by a small amount in the absence of conformational effects.…”

Section: -T-butylcyclohexyl Acetates (91)mentioning

confidence: 99%

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Syntheses and eliminations of cyclopentyl derivatives

Rausch

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Section: H-c-c+supporting

confidence: 89%

Section: H-c-c+supporting

confidence: 84%

Section: H-c-c+mentioning

confidence: 99%

Section: H-c-c+mentioning

confidence: 99%

Section: -T-butylcyclohexyl Acetates (91)mentioning

confidence: 99%

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Syntheses and eliminations of cyclopentyl derivatives

Rausch

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Does side chain water loss from protonated threonine yield N-protonated dehydroamino-2-butyric acid?

O’Hair

Reid

1998

Rapid Commun. Mass Spectrom.

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Electrospray ionization tandem mass spectrometry (ESI-MS/MS) of protonated threonine, isotopically labelled threonine and threonine methyl ester, suggests that side chain water loss occurs via a neighbouring group participation reaction in which the free amino group displaces water from HO-protonated threonine. Ab initio calculations show that the resultant [M H À H 2 O]product ion is a protonated aziridine, which is in contrast to previously published results, which suggested N-protonated dehydroamino-2-butyric acid as the likely structure. # 1998 John Wiley & Sons, Ltd. Received 11 May 1998; Revised 10 June 1998; Accepted 12 June 1998 Tandem mass spectrometry is rapidly becoming an indispensible tool for the structural characterization of proteins, peptides, carbohydrates and oligonucleotides. While the common fragmentation pathways of such compounds have been examined, a more detailed understanding of the complex gas phase reactivities of these compounds (for example, the influence of potentially reactive side chains on 'sequence' ion versus 'non-sequence' ion formation) is required in order to facilitate the elucidation of unknown sequences. As part of our ongoing work into probing the gas phase reactions of biomolecules, we have recently examined both the bimolecular reactivity 1 as well as the collision induced dissociation (CID) reactions of several model peptide systems. 2 In the former studies we demonstrated that the various functional groups present in simple amino acids such as glycine and cysteine can act as intermolecular nucleophiles in gas phase bimolecular alkylation reactions.

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