The direction of platinum-catalysed hydrogenation of an unsymmetrical anhydride in the norbornane series

Abstract

The products of hydrogenation of 2-exo-methylbicyclo[2,2,1]hept-5-ene-2,3-endo-dicarboxylic anhydride (VI) have been shown to be the hemiacylal (VII) and the lactone (IX), both formed by reduction of the less hindered carbonyl group. These structures were assigned by consideration of the N.M.R. spectra of the hemiacylal (VII) and of its ring-opened anion (XI) formed with alkali in water or deuterium oxide. The anion (XI) has been shown to undergo slow base-catalysed isomerization (accompanied, in deuterium oxide, by deuteration at C 3) to give an equilibrium mixture from which has been isolated the trans-isomer, 3-exo-formyl-2-exo-methylbicyclo-2,2,1,heptane-2-endo-carboxylic acid (XIII).