Cyclization reactions of acylium and thioacylium ions with isocyanates and isothiocyanates: Gas phase synthesis of 3,4-dihydro-2,4-dioxo-2H-1,3,5-oxadiazinium ions

Meurer, Eduardo C.; Sparrapan, Regina; Tomazela, Daniela M.; Eberlin, Marcos N.; Augusti, Rodinei

doi:10.1016/j.jasms.2005.05.011

Cited by 8 publications

(6 citation statements)

References 43 publications

(35 reference statements)

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“…With this dienophile, 1 • + also reacts promptly by electron abstraction to form ionized phenyl isocyanate of m / z 119 (Table , entry 13), but the expected polar [3 + 2] cycloaddition occurs competitively, thus yielding the product ion of m / z 239, that is, probably the ionized molecule of 3-phenylbenzo[ e ][1,3]oxazine-2,4-dione (Scheme ). Double addition of a phenyl isocyanate molecule was not observed, which seems to indicate that cycloaddition precludes formation of 3,4-dihydro-2,4-dioxo-2 H -1,3,5-oxadiazinium ions upon reactions at CO + . Dissociation of this cycloadduct occurs predominantly by retroaddition (Table ).…”

Section: Resultsmentioning

confidence: 95%

Intrinsic Gas-Phase Reactivity of Ionized 6-(Oxomethylene)cyclohexa-2,4-dienone: Evidence Pointing to Its Neutral α-Oxoketene Counterpart as a Proper Precursor of Various Benzopyran-4-ones and Analogues

et al. 2007

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Despite its unique structure and potential use as an important building block in organic synthesis, the title alpha-oxoketene 1 has been formed mostly under very special conditions as a short-lived species. The reactivity of 1 is, therefore, nearly unexplored. In great contrast, it seemed that its ionized gaseous form 1*+ is stable and easily accessible. In this study, we used multiple-stage pentaquadrupole mass spectrometry to probe the formation of gaseous 1*+ and explore its stability and intrinsic reactivity. With water and methanol, gaseous 1*+ was found to react similarly to solvated 1, which indicates that there is a close parallel between their reactivities. Gaseous 1*+ was also found to react promptly via polar [3 + 2] cycloadditons with various dienophiles including alkenes, alkynes, isocyanates, ketones and esters, thus forming a series of benzopyran-4-ones (flavones, 4-chromanones, 4-chromenones, benzo[1,3]dioxin-4-ones, and analogues) that are common structural units in many natural products. The present availability of 1 at room temperature and the gas-phase findings reported herein for gaseous 1*+ indicate that solvated 1 should undergo many [4 + 2] cycloadditions and functions as a versatile precursor of a variety of biologically active molecules.

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Section: Resultsmentioning

confidence: 95%

Intrinsic Gas-Phase Reactivity of Ionized 6-(Oxomethylene)cyclohexa-2,4-dienone: Evidence Pointing to Its Neutral α-Oxoketene Counterpart as a Proper Precursor of Various Benzopyran-4-ones and Analogues

et al. 2007

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“…7 Cyclization reactions of acylium and thioacylium ions with isothiocyanates have recently been observed also in the gas phase. 8 In the synthesis of carbocyclic and heterocyclic fused quinolines by cascade radical annulations of unsaturated N-aryl thiocarbamates, the thiocarbamate precursors are prepared by treatment of aryl isothiocyanates with homopropargyl alcohols. 9 Many of these behavioral phenomena are undoubtedly related to their electronic structures and, in particular, to their ability to accept electrons.…”

Section: Introductionmentioning

confidence: 99%

Temporary Anion States and Dissociative Electron Attachment to Isothiocyanates

Modelli

Jones

2006

J. Phys. Chem. A

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The temporary anion states of isothiocyanates CH3CH2=C=S (and CH3CH2N=C=O for comparison), C6H5CH2N=C=S, and C6H5N=C=S are characterized experimentally in the gas phase for the first time by means of electron transmission spectroscopy (ETS). The measured vertical electron attachment energies (VAEs) are compared with the virtual orbital energies of the neutral-state molecules supplied by MP2 and B3LYP calculations with the 6-31G* basis set. The calculated energies, scaled with empirical equations, reproduce satisfactorily the experimental VAEs. The first VAE is also closely reproduced as the total energy difference between the anion and neutral states calculated at the B3LYP/6-31+G* level. Due to mixing between the ring and N=C=S pi-systems, C6H5N=C=S possesses the best electron-acceptor properties, and its lowest-lying anion state is largely localized at the benzene ring. The anion states with mainly pi*C=S and pi*N=C character lie at higher energy than the corresponding anion states of noncumulated pi-systems. However, the electron-acceptor properties of isothiocyanates are found to be notably larger than those of the corresponding oxygen analogues (isocyanates). The dissociative electron attachment (DEA) spectra show peaks close to zero energy and at 0.6 eV, essentially due to NCS- negative fragments. In spite of the energy proximity of the first anion state in phenyl isothiocyanate to the DEA peak, the zero-energy anion current in the benzyl derivative is about 1 order of magnitude larger.

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“…This result demonstrates that the separation of anthocyanidins can be achieved in a much smaller period of time (1.30 min) when compared to the conventional high pressure liquid chromatography (HPLC) runs, which are the most used for this purpose, with analytical runs of approximately 20 to 60 min. 11,[13][14][15] The spectra of fragmentation and product ion spectra obtained by direct infusion of analytical standards of anthocyanidins delphinidin, cyanidin and pelargonidin are shown in Supplementary Information. The mass/charge ratio (m/z) values of these compounds, as well as the fragments resulting from electrospray ionization, were subsequently used in the quantification of these compounds in the samples.…”

Section: Resultsmentioning

confidence: 99%

“…This kind of structure usually fragments into acylium ions. 13 All the structures are rigid, and will need high amounts of energy to be cleaved, especially the closed shell [M + H] + cation fragments obtained by hydrogen rearrangements and induced by charge dissociation. The first proposed dissociation mechanism pathway (I), present the ion of m/z 69 as common for all structures and it is proposed as a stable acylium ion.…”

Section: Resultsmentioning

confidence: 99%

Simple and Fast Method for Identification and Quantification of Anthocyanidins in Berries by Ultra Performance Liquid Chromatography-Mass Spectrometry

Vagula

Sinosaki

Ribeiro

et al. 2017

J. Braz. Chem. Soc.

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The objective was identifying three different anthocyanidins and to quantify them in six different berries. Results from the conventional method (using extraction with hydrochloric acid) were compared with data from the proposed method (without acid extraction). The following figures of merit were used: linearity, accuracy, linear range, limits of detection and quantification, using an ultra performance liquid chromatography (UPLC) coupled to a triple quadrupole mass spectrometer equipped with an electrospray ionization source. The separation of anthocyanidins can be achieved in a much smaller period of time (1.30 min) and the cyanidin from Morus nigra L., Rubus idaeus L. and Vaccinium myrtillus L. was found in higher amounts in extracts obtained from the proposed method. Proposed mechanisms of mass spectrometry (MS/MS) collisional induced dissociation for pelargonidin, cyanidin and delphinidin were obtained and this is the first time that concentrations of anthocyanidins present in fruits of Solanum americanum Mill. were reported.

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Cyclization reactions of acylium and thioacylium ions with isocyanates and isothiocyanates: Gas phase synthesis of 3,4-dihydro-2,4-dioxo-2H-1,3,5-oxadiazinium ions

Cited by 8 publications

References 43 publications

Intrinsic Gas-Phase Reactivity of Ionized 6-(Oxomethylene)cyclohexa-2,4-dienone: Evidence Pointing to Its Neutral α-Oxoketene Counterpart as a Proper Precursor of Various Benzopyran-4-ones and Analogues

Intrinsic Gas-Phase Reactivity of Ionized 6-(Oxomethylene)cyclohexa-2,4-dienone: Evidence Pointing to Its Neutral α-Oxoketene Counterpart as a Proper Precursor of Various Benzopyran-4-ones and Analogues

Temporary Anion States and Dissociative Electron Attachment to Isothiocyanates

Simple and Fast Method for Identification and Quantification of Anthocyanidins in Berries by Ultra Performance Liquid Chromatography-Mass Spectrometry

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