Reaction of functionalized organolithium compounds with substituted oxiranes: useful methodology for 1,6- and 1,7-diols, and tetrahydrobenzoxepines

The reaction of dianions , derived from the reductive opening of phthalan () or isochroman () with lithium and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB) at 0°C, with several epoxides at the same temperature gave, after hydrolysis, 1,6- and 1,7-diols, respectively. Dehydration of 1,6-diols by treatment with BF3·OEt2 in dichloromethane at temperatures ranging from −30 to 20°C gave tetrahydrobenzoxepines in very good yields. Under the same reaction conditions 1,7-diols did not undergo dehydration.