Cyclization of hindered fluorinated dichloro(5- and 6-)alkenyl radicals. Structural effects of olefins on the selective formation of 5-exo and 6-endo cyclization products

摘要

Reaction of 3-butenyl radicals generated by photolysis of variously substituted Barton esters (both open-chain 1a-d and cyclohexyl 1e-h) with CF_2=CCI_2 gave a mixture of cyclized products (cyclopentanes 6 and 8 and cyclophexanes 7 and 9) as well as noncyclized products (4 and 5) in various rations depending on the substitution pattern at the olefinic moiety. The products rations of [cyclization (6+7+8+9):noncyclization (5)] for 1 with more alkyl substituents on the CC double bond were greater than those for 1 with fewer substituents.