Mass spectrometry of negative ions and the stereochemistry of organic compounds. IV. Acetates of epimeric diterpene glycols

Summary 1. It has been established that the fragmentation of the molecular negative ions of the diacetates of sclareol and of 13-episclareol takes place with the splitting out of the fragments Ac, OAc, CH₂CO, AcOH, CH₃, and CH=CH₂ without skeletal rearrangements.2. The relative yields of the negative ions formed depend on the stereochemistry of the molecules of the compounds investigated.Institute of Chemistry, Bashkir Branch of the Academy of Sciences of the USSR, Ufa. Institute of Chemistry, Academy of Sciences of the Moldavian SSR, Kishinev. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 454–457, July–August, 1978.     

Fragmentation processes in phthalimide- and pyridine-2,3-dicarboimidoalkyl-α-diazoketones under resonant electron capture

Resonant electron capture (REC) mass spectra of phthalimide- and pyridine-2,3-dicarboimidoalkyl-α-diazoketones have been investigated. Based on calculations using the Hartree–Fock method and density functional theory with the B3LYP functional the structure of the negative ions (NIs) [M–N₂]^? and [M–N₂–C₃H₃RO]^? as well as the reactions leading to their formation have been proposed.     

Resonance capture of electrons by molecules of substituted pyrans

Negative-ion mass spectrometry in the mode of resonance capture of electrons and photoelectron spectroscopy in combination with quantum-chemical calculations showed that the formation of the resonance states of negative molecular ions in the reaction of electrons with molecules of the mechanism of intershell Feshbach resonance with the consecutive excitation of an electron from several higher occupied MO to one vacant MO. In a low-energy region, the resonance at 1.4 eV is a resonance of form and the resonance at 3–4 eV is the usual electron exciting Feshbach resonance with a parent triplet state (π.π*)³. The one and the same vacant π*_CC MO is “active” in all the resonances mentioned. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1892–1894, October, 1997.     

Features of mass-spectrometric fragmentation of racemic diptocarpidine and diptocarpiline

The mass-spectrometric fragmentation of the positive and negative molecular ions of diptocarpidine and diptocarpiline and of two model compounds have been studied, and it has been shown that the formation of the fragmentary ions takes place both by direct bond cleavage and with the involvement of complex skeletal rearrangements. The composition of the rearranged ions formed from M⁺ has been confirmed with the aid of high-resolution mass spectrometry. An intramolecular interaction of the this (sulfoxy) and urea groups as a consequence of the existance of the molecules under investigation in a folded conformation has been established.Institute of Chemistry Bashkir Branch USSR Academy of Sciences, Ufa. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 390–396, May–June, 1988.     

Negative-ion mass spectrum of some analogs of 11-deoxyprostaglandins E1

The results of a study of the mass spectra of the negative ions formed in the dissociative capture of electrons by the molecules of some analogs of 11-prostaglandins E₁ have shown that from the fragments of the compound under consideration it is possible to single out two centers of electron capture: R and the remaining fragment of the molecule. The presence of fragments characteristic for each group of processes and their simplicity and distinctness permit this method to be used successfully for determining the structures of compounds of the given class.Institute of Chemistry, Bashkir Branch, Academy of Sciences, Ufa. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 757–760, November–December, 1985.     

Resonance electron capture by the molecules of α- and β-C(14)-methoxy isomers of 10,12-dehydro-8,9-seco-8,9-dioxolappaconine and its oxo derivative

The formation of negative ions of some diterpene alkaloid molecules having conjugated π_С=С and π_С=О bonds in their structure by resonance electron capture has been studied. The mass spectra of these compounds are due to electron capture onto the lowest unoccupied molecular orbital (LUMO), which is π*-_С=С or π*-_С=О in nature. It has been found that the partial conversion of the test compound molecules into the enol form is possible on transferring into a gas phase; for this purpose, the appearance potentials of the ions (M–H)^– and (M–OCH₃)^– have been compared with the calculated thermodynamic thresholds of their appearance in the keto and enol forms.     

Synthesis of ethophenprox analogs

The synthesis of ethophenprox analogs was performed by condensation of alcohols with benzyl halides under conditions of the phase transfer catalysis. The ultrasonic irradiation was shown to accelerate the reaction and to increase the yield of ethers. The trends in fragmentation of new generation pyrethroids under the electron impact were established. Insecticidal activity of the compounds obtained was evaluated.