- Small Rings, 89. - An Alternative Synthesis of Tetra-tert-butyltetrahedrane
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Cyclopropenyldiazomethane 3 is an ideal precursor for tetra-tert-butyltetrahedrane (6).Both, photochemical and thermal decomposition of 3 lead to cyclobutadiene 7, which can be photoisomerized to tetrahedrane 6.Tetra-tert-butyltetrahedrane (6) is also formed directly by a cheletropic cycloaddition of the carbenic center to the cyclopropene double bond in carbene 4.This is the first example for the synthesis of a tetrahedrane, which does not occur via the corresponding cyclobutadiene.The formation of pyridazine 10 dominates the thermolysis of 3.Azete 12 is obtained both by photolysis as well as by thermolysis of Dewar-pyridazine 11, the irradiation product of 10. - Key Words: Cyclobutadiene / Tetrahedrane / Azete / Cyclopropenyldiazomethane / Valence isomers of pyridazine
- Maier, Guenther,Fleischer, Frank
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p. 169 - 172
(2007/10/02)
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- Small Rings, 78. - Tri-tert-butyl(trimethylsilyl)cyclobutadiene and Tri-tert-butyl(trimethylsilyl)tetrahedrane
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The chemistry of diazo(1,2,3-tri-tert-butylcyclopropenyl)(trimethylsilyl)methane (6) is unexpectedly diverse.Upon irradiation it fragments exclusively into the acetylenes 7 and 8.Flash thermolysis, on the other hand, gives - aside from the two acetylenes - tri-tert-butylazete (10) and trimethylsilyl cyanide (11).Upon heating 6 presumbaly isomerizes via betaine 17 to Dewar-diazabenzene 13 - which is split into 10 and 11 - and diazabenzvalene 18.This reaction course is supported by the isolation of the carbonyliron complexes 15 and 16. - The CuCl-catalyzed thermal decomposition again follows a different route.Under these conditions tri-tert-butyl(trimethylsilyl)cyclobutadiene (5) is formed, probably as a weak CuCl complex.Only after addition of ethylenebis(diphenylphosphane) free cyclobutadiene 5 can be isolated.Upon irradiation of 5 a quantitative isomerization to tri-tert-butyl(trimethylsilyl)tetrahedrane (29) occurs.This second, spectroscopically unequivocally confirmed tetrahedrane melts at 179 deg C.In solution the isomerization to cyclobutadiene 5 starts at about 160 deg C.That means, it is thermally even more stable than tetra-tert-butyltetrahedrane. - Key Words: Diazo compounds / Transition-metal complexes / Photoisomerization / Homocyclopropenylium ions
- Maier, Guenther,Born, Dieter,Bauer, Ines,Wolf, Reinhard,Boese, Roland,Cremer, Dieter
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p. 173 - 190
(2007/10/02)
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Diazocompound 1 turns out to be the ideal photochemical precursor for tetrahedrane 3. Upon thermolysis Dewarpyridazine 6 is fragmented quantitatively into tri-tert-butylazete 8 and pivalonitrile 9.
- Maier, Guenther,Fleischer, Frank
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