<i>Ortho</i> effects in organic molecules on electron impact: 18—Novel hydrogen transfer from the methoxy group to acetylenic carbon in 2‐methoxyphenylacetylene and 2‐methoxydiphenylacetylenes

Ramana, D. V.; Krishna, Nunna V.

doi:10.1002/oms.1210240505

Cited by 11 publications

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References 20 publications

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“…Changing the alkyl groups, a slightly better transformation was recorded with 4-ethyl phenylacetylene (Table 2, entry 1f). The inert and difficult-to-activate molecules such as 4-methoxy and 2-methoxy substituted phenylacetylene showed efficient transformations of 87% and 84% for the desired product (Table 2, entries 1g and 1h) [64][65][66]. The halides, 4-fluoro, 4-chloro, and 4-bromophenylacetylene also reacted and showed 86, 80, and 74% transformations of the respective keto products (Table 2, entries 1i-1k).…”

Section: Resultsmentioning

confidence: 99%

Facile Photochemical/Thermal Assisted Hydration of Alkynes Catalysed under Aqueous Media by a Chalcogen Stabilized, Robust, Economical, and Reusable Fe3Se2(CO)9 Cluster

et al. 2023

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In this report, the catalytic potential of chalcogen-stabilized iron carbonyl clusters [Fe3E2(CO)9 (E = S, Se, Te)] for the photolytic hydration of alkynes has been explored. The iron chalcogenide clusters bring excellent transformations of terminal and internal alkynes to their respective keto products in just 25 min photolysis at −5 °C in inert free and aqueous conditions. After the completion of the reaction, the product can be extracted from organic solvent, and due to the lower solubility of the catalyst in water, it can also be isolated and further reused several times prior to any activation. The catalyst was also found to be active in thermal conditions and bring about the desired transformations with average to good catalytic efficiency. Moreover, during the thermal reaction, the catalyst decomposed and formed the nanoparticles of iron selenides, which worked as a single-source precursor for FeSe nanomaterials. The presented photolysis methodology was found to be most feasible, economical, instantly produce the desired product, and work for a wide range of internal and terminal alkynes; hence, all these features made this method superior to the other reported ones. This report also serves as the first catalytic report of chalcogen-stabilized iron carbonyl clusters for alkyne hydrations.

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Section: Resultsmentioning

confidence: 99%

Facile Photochemical/Thermal Assisted Hydration of Alkynes Catalysed under Aqueous Media by a Chalcogen Stabilized, Robust, Economical, and Reusable Fe3Se2(CO)9 Cluster

et al. 2023

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Comparison of gas‐phase basicities and ion–molecule reactions of aminobenzoic acids

et al. 1995

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Functional group interactions and substituent effects of o-, m-and p-aminobenzoic acids were examined in a quadruple ion trap by evaluation of proton-transfer a d methylene substitution reactions. An electron-withdrawing carboxylic acid group can enhance or reduce the gas-phase basicity of aniline depending on its location and ability to participate directly in proton bridging. In fact, the gas-phase basicity of o-aminobenzoic acid is enhanced by -7 kcal mol-' relative to the metu and para isomers in which the substituents do not have cooperative functional group interactions. Collisionally activated dissociation studies of deuterium-labeled ions provide evidence of proton migration from the amino group to the carboxylic acid group prior to fragmentation. Results of semi-empirical molecular orbital calculations provided structures for the various protonated aminobenzoic acids. For oaminobenzoic acid, the proton bridges between the acid and amine groups. I N T R O D U C T I O NHydrogen bonding is among the most important types of interactions in organic and biological chemistry. '-'Numerous recent studies have begun to address the significance of hydrogen bonding interactions in gas-phase ions, especially with respect to the influence on gasphase basicities, cluster formation and s~l v a t i o n .~~~' The evaluation of intramolecular hydrogen bonds has become increasingly common recently owing to the advent of electrospray ionization and the formation of multiply protonated molecules, such as proteins. Studies have shown that when two or more functional groups coexist in a compound, the interaction among neighboring functional groups affects the physical properties and chemical rea~tivities,''-'~ such as in the well known ortho effect.' 9-25 Therefore, it is reasonable to predict that the basicity of a compound depends not only on the nature of the functional groups, but also on the relative positions and orientations of the groups within the compound. For example, it is well accepted that diamines typically have greater gas-phase basicities than amines because of the ability of a protonated diamine to undergo cyclization via proton bridging between the two amine groups7 It has been found that the strain energy in cyclic protonated diamines ranges from 2.5 to 10.4 kcal mol-I (1 kcal = 4.184 kJ) depending on the ring size, whereas the formation of the intramolecular hydrogen bonds can stabilize the ions by up to 20 kcal mol-'." Another group reported the cyclization enthalpy resulting from proton bridging between two interacting amine groups to range from -5 to -17 kcal mol-' depending on the geometry of the hydrogen bond. l 6 Additionally, from measurements on the proton-transfer equilibria of a series of polyethers, it was found that basic molecules that could participate in multi-coordination of a proton have enhanced proton affinities but suffer a decrease in entropy owing to the enforced organization of the polyether structures." For instance, the enthalpy of the intramolecular hydrogen bond in protonated poly...

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Intramolecular aromatic substitution and amino‐Claisen rearrangement in substituted N‐(2‐propynyl)anilines on electron impact

Ramana

Sudha

1995

J. Mass Spectrom.

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N-(2-Propynyl)anilines undergo amino-Claisen rearrangement to a minor extent in the ion source, losing a molecule of HCN under electron impact conditions. However, metastable molecular ions with energies closer to threshold undergo Claisen rearrangement giving rise to more abundant [ M -HCN I +' ions in the first field-free region.Loss of a hydrogen from the molecular ion gives rise to the base peak in the mass spectrum of N42-propyny1)aniline. The hydrogen that is expelled for the formation of the [ M -HI+ ion is observed to be from the amino nitrogen, propargylic carbon and the ortho-carbon of the ring. The last process leads to a cyclic fragment involving intramolecular aromatic !substitution. Double oxygen migration from the nitro group to the triple bond, due to the ortho effect, yields an abundant ion a t m/z 105 in N-(2-propynyl)-o-nitroaniline. The proposed fragmentation pathways and ion structures are substantiated by high-resolution data, B/E and B2/E linked-scan spectra, collisionally activated dissociation-,B/E linked-scan spectra and deuterium isotopic labelling.

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Ortho effects in organic molecules on electron impact: 18—Novel hydrogen transfer from the methoxy group to acetylenic carbon in 2‐methoxyphenylacetylene and 2‐methoxydiphenylacetylenes

Cited by 11 publications

References 20 publications

Facile Photochemical/Thermal Assisted Hydration of Alkynes Catalysed under Aqueous Media by a Chalcogen Stabilized, Robust, Economical, and Reusable Fe3Se2(CO)9 Cluster

Facile Photochemical/Thermal Assisted Hydration of Alkynes Catalysed under Aqueous Media by a Chalcogen Stabilized, Robust, Economical, and Reusable Fe3Se2(CO)9 Cluster

Comparison of gas‐phase basicities and ion–molecule reactions of aminobenzoic acids

Intramolecular aromatic substitution and amino‐Claisen rearrangement in substituted N‐(2‐propynyl)anilines on electron impact

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