Disubstituted-bicyclooctanes

The decomposition of adducts of 1,5-cyclooctadiene to give 3.3.0-octanes has precedent. Thus, Anderson and Burreson (5) decomposed the oxymetallation adduct by light to give an unsaturated bicyclooctane, whereas Takahashi and Tsuji (253) used strong base to produce a disubstituted bicyclooctane. Both reactions must also occur by addition of Pd(II)-C bonds across the second olefinic bond as in Eqs. (205) and (206). 

These effects can occur when the active site at which a measurable phenomenon occurs is in close proximity to the substituent. Among the many systems exhibiting direct steric effects are ortho-substituted benzenes, 1, cis-substituted ethylenes, 2, and the ortho- (1,2-, 2,1- and 2,3-) and peri- (1,8-) substituted naphthalenes, 3, 4, 5 and 6, respectively. Other examples are d.v-1,2-disubstiUited cyclopropanes, c/ s-2,3-disubstituted norbornanes and ci.s-2,3-disubstituted [2.2.2]-bicyclooctanes, 7, 8 and 9, respectively. Some systems generally do not show steric effects. Vicinally substituted systems such as disubstituted methanes, 10, and 1,1-disubstituted ethenes, 11, are examples, 2,3-Disubstituted heteroarenes with five-membered rings such as thiophenes and selenophenes... 

In Charton s work pKa data for 4-X-substituted-bicyclo[2.2.2.]octane-l-carboxylic acids in 50% w/w EtOH-H20 are the basis for primary molecular skeleton, the substituent is somewhat remote from the acidic centre and the geometry for 4-X and 1-COOH closely resembles that for groups in a 1,4-disubstituted benzene)81. However, the pKa value for the vinyl-substituted acid in this solvent was not available, so the 07 value for the vinyl group was calculated by substituting the pKa value for vinylacetic acid in water at 25 °C (4.352) in the regression equation 10 ... 

---