Bicycloheptane and Bicyclo-octane Derivatives

Bicycloheptane and Bicyclo-octane Derivatives.—Relative positional reactivities in nitration of benzonorbornene, benzonorbornadiene, (727), and the endo-isomer of (727) have been determined for the ipso-, a-, and /S-positions. The lower a-reactivity of (727) as compared to its endo-isomer is explained by the buttressed fused ortho effect , arising in (727) because steric hindrance between bridge and cyclopropane methylene hydrogens is sufficient to cause bridge bending, thus moving the sy -H 

respectively.The radical (730), formed by thermolysis of the tricyclo-octene-carboxylic acid t-butyl perester, is found to be more stable toward ring cleavage than the analogous saturated radical or the endo-isomer of (730) hyperconjugative stabilization of (730) is therefore suggested.  

Numerous new examples of cyclopentenone synthesis from acetylenehexacarbonyl-dicobalt complexes and norbornene derivatives have been disclosed there is evidence of steric control, and the bulky trimethylsilyl group can be employed as a removable direction-determining group to allow synthesis of 3- instead of 2-sub-stituted cyclopentenones. Reaction of (731) with sodamide in toluene gave the new octahydro-2,5-methanoazulene system (732 R = CONHj) successive hydrolysis, reduction, and esterification converted (732 R = CONHj) into (732 R = CHjOTs) which, on solvolysis, gave the homoprotoadamantane derivative (733 X = H, R R = CH2) in high yield.The carboxylic acid (732 R = COjH) underwent spontaneous Friedel-Crafts intramolecular acylation on conversion into its acid chloride to give (733 XX = O R R = CHj) and (733 XX = O, R = Cl, R = Me). Reaction of methyl a-bromocrotonate (mixture of E- and Z-isomers) with the enolates of cyclohex-2-enone affords a mixture of stereoisomeric tricyclo-[3,2,l,0 ]octan-6-ones (734 R —R are variously H or alkyl) in moderate yield. The reaction involves double Michael addition and subsequent substitution. 

A detailed study of the effectiveness of new reagents for the inter- and intramolecular pinacolic coupling of aldehydes and ketones has been published,  

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