- Mechanism of the Cyclopropane "Walk" Rearrangement: Syntheses and Properties of 2-Diazopropane-Arene Adducts; a Regiospecific N2 Elimination
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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.
- Klaerner, Frank-Gerrit,Glock, Volker,Hemmes, Jan-Luiken
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p. 1869 - 1879
(2007/10/02)
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