Radical cyclization in heterocycle synthesis. 11.(1) A novel synthesis of alpha,beta-disubstituted gamma-lactones via sulfanyl radical addition-cyclization using hydroximates as a tether
A combination of sulfanyl radical addition-cyclization of dienes connected with hydroximates and subsequent conversion of the resulting cyclic hydroximate to the lactones provides a novel method for the construction of alpha,beta-disubstituted gamma-lactones. Upon treatment with thiophenol in the presence of AIBN, dienes connected with hydroximates smoothly underwent sulfanyl radical addition-cyclization to give cyclic cis- and trans-hydroximates. Hydrolysis of cyclic hydroximates gave the desired cis- and trans-lactones in high yield. This method was successfully applied to the practical synthesis of (+/-)-oxo-parabenzlactone.
Miyata
O
Kobe Pharmaceutical University, Motoyamakita, Higashinada, Kobe 658-8558, Japan, and Analytical Research Laboratory, Tanabe Seiyaku, Co. Ltd., Kashima, Yodogawa, Osaka 532-0031, Japan.
Nishiguchi
A
Ninomiya
I
Aoe
K
Okamura
K
Naito
T