252922-00-2Relevant academic research and scientific papers
Thermal decomposition of strained spiro(1-pyrazoline-3,1'-cyclopropanes)
Tomilov, Yu. V.,Shulishov, E. V.,Yarygin, S. A.,Nefedov, O. M.
, p. 2109 - 2113 (1995)
Pyrolysis (320-370 deg C) of polycyclic 1-pyrazolines 1 and 2, obtained by 1,3-dipolar cycloaddition of diazocyclopropane to 3,3-dimethylcyclopropene and spirohex-1-ene, yields complex mixtures of isomeric hydrocarbons, substituted methylenecyclopropanes being the main components.Pyrolysis of 6-ethenyl- (4) and 6-methoxy-6-methylcarbonyl-4,5-diazaspirohept-4-enes (6) at 310-320 deg C proceeds unambiguously to give vinyl- (18) and 1-methoxy-1-methylcarbonylspiropentanes (20) in ca. 85 and 95 percent yields with respect to the transformed pyrazolines.Dediazotization of pyrazoline 3 obtained from diazocyclopropane and benzvalene requires more drastic conditions (-440 deg C) and produces indane. - Keywords: spiro(1-pyrazoline-3,1'-cyclopropanes; methylenecyclopropanes and spiropentanes; pyrolysis; isomerization; NMR spectra.
Notable effect of an electron-withdrawing group at C3 on the selective formation of alkylidenecyclobutanes in the thermal denitrogenation of 4-spirocyclopropane-1-pyrazolines. Nonstatistical dynamics effects in the denitrogenation reactions
Hamaguchi, Masashi,Nakaishi, Masahiro,Nagai, Toshikazu,Nakamura, Takeshi,Abe, Manabu
, p. 12981 - 12988 (2008/09/17)
A detailed study of the thermal denitrogenation of 3-carbomethoxy- substituted 4-spirocyclopropane-1-pyrazolines 6 was conducted. Alkylidenecyclobutane derivatives 7 were selectively formed in a stereospecific manner. Unrestricted density functional calculations for a 1-pyrazoline 10a indicated that the concerted cleavage of two C-N bonds is the energetically favored process for the denitrogenation reaction to give the 2-spirocyclopropyl 1,3-diyl, followed by a conrotatory ring-closure process, which was calculated to be the energy minimum pathway, to afford a spiropentane derivative. The calculated energy minimum pathway is largely inconsistent with the experimental results observed for the denitrogenation of 6 and 10a. The contradiction between the experimental and standard computational results was solved by considering nonstatistical dynamics effects in the concerted denitrogenation reactions. Although the energy minimum pathway from the transition states of the concerted denitrogenation of the 3-carboalkoxy-substituted 1-pyrazolines involves generation of the corresponding 1,3-diradicals, many trajectory calculations using the Bohn-Oppenheimer molecular dynamics model from the transition state for the concerted denitrogenation led directly to the formation of alkylidenecyclobutanes at the UB3LYP/6-31G(d) level of theory.
Formation and thermal decomposition of adducts of phthalimidonitrene with spiro(1-pyrazolinecyclopropanes)
Tomilov,Kostyuchenko,Shulishov,Averkiev,Antipin,Nefedov
, p. 1316 - 1322 (2007/10/03)
Oxidation of N-aminophthalimide with lead tetraacetate in the presence of spiro(1-pyrazolinecyclopropanes) at temperature from -20 °C to -30 °C resulted in the formal generation of phthalimidonitrene followed by its addition at the N=N bond of the pyrazoline ring to form 5(3)-substituted N-{spiro[1-pyrazolinio-3(5),1′-cyclopropane]}-N-phthalimidoamides (azimines), whose regioisomeric compositions were determined to a large extent by the nature of the substitueras in the pyrazoline ring. The structures of phthalimidoazimines were established based on the NMR spectra and X-ray diffraction data. Thermal conversions of the resulting adducts, which proceeded either with retention or with opening of the spiro-fused cyclopropane ring, were studied.
