SMALL RINGS .89. AN ALTERNATIVE SYNTHESIS OF TETRA-TERT-BUTYLTETRAHEDRANE

Cyclopropenyldiazomethane 3 is an ideal precursor for tetra-tert-butyl tetrahedrane (6). Both, photochemical and thermal decomposition of 3 l ead to cyclobutadiene 7, which can be photoisomerized to tetrahedrane 6. Tetra-tert-butyltetrahedrane (6) is also formed directly by a chele tropic cycloaddition of the carbenic center to the cyclopropene double bond in carbene 4. This is the first example for the synthesis of a t etrahedrane, 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.