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

Abstract

The reaction of dianions 2 , derived from the reductive opening of phthalan ( 1a ) or isochroman ( 1b ) with lithium and a catalytic amount of 4,4′-di- tert-butylbiphenyl (DTBB) at 0°C, with several epoxides 3 at the same temperature gave, after hydrolysis, 1,6- and 1,7-diols, respectively. Dehydration of 1,6-diols by treatment with BF 3·OEt 2 in dichloromethane at temperatures ranging from −30 to 20°C gave tetrahydrobenzoxepines 5 in very good yields. Under the same reaction conditions 1,7-diols 4 did not undergo dehydration.