7557-11-1Relevant academic research and scientific papers
Mechanism of the Cyclopropane "Walk" Rearrangement: Syntheses and Properties of 2-Diazopropane-Arene Adducts; a Regiospecific N2 Elimination
Klaerner, Frank-Gerrit,Glock, Volker,Hemmes, Jan-Luiken
, p. 1869 - 1879 (2007/10/02)
The synthesis and the thermal and photochemical behavior of 2-diazopropane adducts of toluene 1a, m-xylene 1b,c, and Dewar benzene 2a,b are reported.At 60 deg C the thermal N2 elimination of the specifically deuterated compound 1c proceeds regiospecifically leading to 1,7,7-trimethyl-5-(trideuteriomethyl)-1,3,5-cycloheptatriene (12c), whereas the photolysis of 1c sensitized by benzophenone yields both regioisomeric cycloheptatrienes 12c and 13c in a 51:49 ratio.This finding excludes the symmetrical diradical 3c as an intermediate in the thermal N2 elimination of 1c and suggests a novel pericyclic process for it.The formation of both regioisomeric cycloheptatrienes 25b and 25c in a 74:26 ratio in the thermolysis of the diazopropane-tetradeuterio Dewar benzene adduct 2b indicates that in this case a multi-step N2 elimination passing through the diradical intermediate 3e competes with the concerted process.According to force-field calculations the course of the N2 elimination in 1a-e might be controlled by the conformational equilibrium A B.
A Convenient Preparation of 7,7-Dimethyl-1,3,5-cycloheptatriene
Rigby, James H.,Bellemin, Anne-Roberte
, p. 188 - 189 (2007/10/02)
Described is a four-step synthesis of 7,7-dimethyl-1,3,5-cycloheptatriene, which starts from readily available 1,4-cyclohexadiene.Monocyclopropanation of this compound with dibromocarbene followed by replacement of the halogens with methyl groups using a higher order cuprate reagent provides the corresponding norcarene which is subjected to a bromination-dehydrobromination sequence to give the title compound.
Stereochemistry and Product Distribution in the Singlet Oxygen Cycloaddition with 7,7-Disubstituted 1,3,5-Cycloheptatrienes
Adam, Waldemar,Adamsky, Friedhelm,Klaerner, Frank-Gerrit,Peters, Eva-Maria,Peters, Karl,et al.
, p. 1848 - 1859 (2007/10/02)
The photosensitized singlet oxygenation of 7,7-dimethyl-(1a), 7-(methoxycarbonyl)-7-methyl- (1b), 7-methyl-7-phenyl- (1c), and 7--7-methyl- (1d) 1,3,5-cycloheptatrienes has been investigated.While 1b - 1d give only the respective norcaradiene endoperoxides 2b-N - 2d-N, the dimethyl derivative 1a affords a 60 : 40 mixture of tropilidene (2a-T) and norcaradiene (2a-N) endoperoxides.In addition to full spectral characterization, the norcaradiene endoperoxides 2b-N - 2d-N were thermally isomerized to their diepoxides 3b - 3d.X-ray analysis confirmed that for 3b the stereochemistry of the substituents is 7-endo-methyl and 7-exo-methoxycarbonyl and for 3c it is 7-endo-phenyl and 7-exo-methyl, showing that the steric size of the substituents in the cycloheptatrienes is Ph Me CO2Me.While the tropilidene endoperoxide 2a-T was a stable compound and could be fully characterized, the norcaradiene derivative 2a-N was too labile and had to be reduced with diimide to the saturated endoperoxide 4a to enable complete characterization.It is shown that the cycloaddition of singlet oxygen is a useful method to assess qualitatively the substituent effects on the tropilidene-norcaradiene valence isomerization, especially for those cycloheptatrienes in which the N/T ratio is too low for measurement by dynamic NMR methods.Stabilization of the norcaradiene isomer by 7-methyl substitution is rationalized in terms of steric effects.
