ISOMERIZATION-REACTIONS OF DICYCLOPENTADIENE DERIVATIVES - PREPARATION OF AMIDES AND CARBOXYLIC-ACIDS

The dicyclopentadiene (DPD) derivatives 8,9-endo-dihydro-DPD (1), 8-exp-hydroxy-exo-tetrahydro-DPD (2) and 2-hydroxy-endo-tetrahydro-DPD (3) have been reacted with acetonitrile in sulfuric acid. Reaction for 6 h at 30-degrees-C gave an 82% yield of N-(2-exo-tetrahydro-DPD-yl)acetamide (5a). Reaction of 3 for 1 min at 20-degrees-C gave N-(2-endo-tetrahydro-DPD-yl)acetamide (4a, 95% yield) and reaction of 2 with acetonitrile and boron trifluoride in sulfur dioxide gave a 95% yield of N-(exo-8-exo-tetrahydro-DPD-yl)acetamide (6a). The reactions of 3 with benzonitrile and substituted benzonitriles were monitored by H-1 NMR spectroscopy. The observed rate constants could be correlated by the Hammett sigma- constants with a rho constant of 1.00 (R2 = 0.987). These results were in accordance with a reaction scheme in which the isomerisations proceed via carbocations in equilibria with nitrile adducts. Reaction of 8-exo-chloro-exo-tetrahydro-DPD (13) with carbon monoxide and antimony pentafluoride in sulfur dioxide gave 2-carboxy-endo-tetrahydro-DPD (15) at -78-degrees-C and 2-carboxy-exo-2-tetrahydro-DPD (17) at 20-degrees-C.