Photochemical Chlorocarbonylation of HCTD by Oxalyl Chloride. Carbocation-Mediated Rearrangement of HCTD Derivatives to Novel, Substituted Heptacyclopentadecanes

Photochemical chlorocarbonylation of heptacyclo[6.6.0.0.^2,60.^3,130.^4,110^5,9.0^10,14]tetradecane (“HCTD”, 1), performed by irradiating a solution of oxalyl chloride and 1 in benzene, followed by reaction of the crude reaction product with methanol, afforded a mixture of methyl 1- and 7-(HCTD)carboxylates (i.e., 2 and 3, product ratio 2/3 = 3:1). Reduction of the mixture of cage esters thereby obtained with LiAlH₄ afforded the corresponding cage alcohols (4 and 5, respectively), which could be separated via column chromatographic methods. Subsequently, 4 and 5 were converted into the corresponding cage tosylates (i.e., 7 and 13, respectively). Reaction of 7 with CF₃CO₂H−CHCl₃ resulted in solvolysis with concomitant skeletal rearrangement, thereby affording 8a. The corresponding reaction performed by starting with cage tosylate 13 also resulted in solvolysis with accompanying skeletal rearrangement, thereby affording 18a.