Methylenevinylcyclopropane

Shields, T. C.; Billups, W. E.; Lepley, Arthur R.

doi:10.1021/ja01019a056

Cited by 54 publications

(11 citation statements)

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“…Another hypothesis (45) has been put forward to explain the observed variations with temperature of the shifts of protons involved in hydrogen bonds that does not involve the rupture (43,46) of these bonds but depends on the degree of excitation of the hydrogen-bondstretching-vibrational modes. Applying this theory to peptides in a hydrogen-bond promoting solvent such as CDCl3, any hydrogenbonded amide protons will be expected to display a higher temperature coefficient than free amide protons, not because of the rupture of the hydrogen bonds but because of their of "-methylamides and the tripeptide methyl bonds (48)(49)(50)(51)(52). The ratio of the integrated intensities of the hydrogen bonded to free NH groups (AH/AF) (53, 54) was 1.4 kO.1 for the dipeptide and tripeptide methyl ester and 2.1 f 0.2 for the tripeptide methylamide over the concentration range studied.…”

Section: Assignment Of Nh Resonancesmentioning

confidence: 99%

Solution conformations of oligomers of α ‐aminoisobutyric acid°

Paterson

Stimson

Evans

et al. 1982

International Journal of Peptide and Protein Research

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The N‐acetyl(Aib)nN' ‐methylamides (with n= 1, 2 and 3) and the N‐acetyl‐(Aib)3 methyl ester have been synthesized using an oxazolone procedure. An experimental conformational analysis of this series of oligomers has been carried out in water, DMSO‐d6 and CDCI3 using n.m.r. techniques, and in chloroform using i.r. spectroscopy. Deuterium exchange rates of amide protons in DMSO‐d6 and the rates of change of these proton chemical shifts with temperature in water, DMSO‐d6 and CDCI3 indicate that the oligomeric N'‐methylamides adopt conformations that have no hydrogen bonds when n = 1, one hydrogen bond when n = 2, and two hydrogen bonds when n = 3, and that Ac(Aib)3OMe has a conformation with one hydrogen bond. An analysis of the N‐H stretching region of the i.r. spectra of these compounds in CHCI3 also suggests the existence of these conformational states. These data imply that the peptides adopt the 310‐helical and not the α‐helical conformation in solution. This conclusion supports the hypothesis that the Aib residue has asymmetric geometry at the Cα atom in solution, similar to that reported in the literature for the crystalline state.

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Section: Assignment Of Nh Resonancesmentioning

confidence: 99%

Solution conformations of oligomers of α ‐aminoisobutyric acid°

Paterson

Stimson

Evans

et al. 1982

International Journal of Peptide and Protein Research

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“…Replacement of halogen by alkoxy and alkylthio groups has been achieved in some cases but is frequently accompanied by elimination. They are also formed by treatment of some halocyclopropanes with base, probably by way of cyclopropene intermediates (197)(198)(199) They are also formed by treatment of some halocyclopropanes with base, probably by way of cyclopropene intermediates (197)(198)(199) …”

Section: >=< + :Cxymentioning

confidence: 99%

Addition to Alkenes

Kirmse

1971

Carbene Chemistry

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“…thermal ring-opening, [1Ϫ4] allene formation, [5Ϫ8] and reductive dehalogenation, [9Ϫ11] whereas other transformations are more sensitive to the interplay between the reaction conditions and the chemical reactivity of the molecule. [26Ϫ33] Such prototropic reactions occur, for example, when alkylsubstituted 1,1-dichlorocyclopropanes [29,30] and bicyclic compounds possessing a gem-dichlorocyclopropane moiety [31Ϫ33] are exposed to potassium tert-butoxide in dimethyl sulfoxide. When such cyclopropanes contain one or more cyclopropyl hydrogen atoms, the primary reaction is usually β elimination to furnish the corresponding cyclopropene, [12Ϫ22] a reaction which is facilitated by electron-withdrawing substituents on the ring.…”

Section: Introductionmentioning

confidence: 99%

Formation of Acetylenes by Ring-Opening of 1,1,2-Trihalocyclopropanes

Sydnes¹

2000

Eur. J. Org. Chem.

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This review describes studies into the conversion of substituted 1,1,2-trihalocyclopropanes into acetylenic acetals and acetylenic ketals by application of alcohols or alkoxides under basic conditions. The acetal/ketal ratio turned out to depend both on the substituents attached to the ring and on the reaction conditions prevailing during the reaction. Under the right conditions, however, completely regioselective ringopening occurs to give either acetylenic acetals or acetylenic [a] . His main research interest is synthetic chemistry, with particular emphasis on the application of cyclopropanes as starting materials and photochemical transformations as a means to incorporate particular structural features into molecules with regiochemical and stereochemical control. He is also involved in studies of oxidation reactions; these are applied to investigation of the degradation of anthropogenic organic compounds in the laboratory as well as under natural conditions in the marine environment.MICROREVIEWS: This feature introduces the readers to the authors' research through a concise overview of the selected topic. Reference to important work from others in the field is included. 3511ketals, with formation of either no or only minor amounts of other products. The reactions are thought to involve cyclopropene intermediates, which are consumed by nucleophilic attack of alcohol or alkoxide. In some cases, the cyclopropene intermediates rearrange to the corresponding vinyl carbenes, which undergo insertion reactions with protic species present in the reaction mixture and give various 2-propenal derivatives as by-products.

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Methylenevinylcyclopropane

Cited by 54 publications

References 1 publication

Solution conformations of oligomers of α ‐aminoisobutyric acid°

Solution conformations of oligomers of α ‐aminoisobutyric acid°

Addition to Alkenes

Formation of Acetylenes by Ring-Opening of 1,1,2-Trihalocyclopropanes

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