REGIOCONTROLLED HYDROGENOLYSIS OF STRAINED SIGMA-BONDS - APPLICATION TO THE SYNTHESIS OF SYN-TRICYCLO[4.2.1.2,5]DECANE AND ANTI-TRICYCLO[4.2.1.12,5]DECANE AND 2 ELUSIVE CYCLOPENTADIENE DIMERS

Catalytic hydrogenation of hypostrophene over palladium on charcoal resulted in regiospecific σ bond hydrogenolysis to give syn-tricyclo[4.2.1.12, 5]decane (4). Similar treatment of the exo-8-hydroxy derivative furnished syntricyclo[4.2.1.12, 5]decan-exo-3-ol (13a). The latter compound served as precursor to both syn-and anti-tricyclo[4.2.1.12, 5]-dec-3-enes. When pentacyclo[5.3.0.02, 5.03, 904, 8]decane-6, 10-diol (18) was hydrogenated, thedihydro derivative 19a resulted. By a sequence of reactions involving mesylation, displacement by iodide ion, and reductive deiodination, 19a was transformed into in-tricyclo[4.2.1.12, 5]deca-3, 7-diene (1). Warming of 1 to 55-80 °C promotes efficient Cope rearrangement to cis, -sys, cis-tricyclo[5.3.0.02, 6]deca-3, 8-diene (3). Lastly, the behavior of 4 under electrophilic and strongly acidic conditions is described. That neither the bromination of 4 nor its isomerization to adamantane can be effected readily is taken as an indication that this exceptionally highly strained molecule cannot ionize readily and transform itself into more thermodynamically stable cations capable of controlled Wagner-Meerwein shifts. © 1979, American Chemical Society. All rights reserved.