Stereoselective free radical cycloaddition-macrocyclization in facile synthesis of trans-cyclohexano-fused 12-membered crown thioethers
摘要:
Homolytic cycloaddition of dithiols 1,2 derived from trans- and cis-1,2-cyclohexanediols to alkynes, induced by Pr3B-O-2, offers an extremely simple approach to trans- and cis-cyclohexano-fused 12-membered crown thialactones 4a-c-7a-c. The reaction of trans-1 proceeds with pronounced remote 1,6-asymmetric induction to give predominantly (IS*, 6R*, 12S*)-4a-c, while cis-2 reacts nonstereoselectively. Basing an molecular mechanics calculations the stereoselectivity is rationalized as a result of entropy favored pathway of macrocyclization.
Remote asymmetric induction in free radical cycloaddition leading to trans-cyclohexano-fused 12-membered crown thioethers
作者:Emmanuil I. Troyansky、Rustem F. Ismagilov、Yury A. Strelenko、Vyacheslav V. Samoshin、Dmitry V. Demchuk、Gennady I. Nikishin、Sergey V. Lindeman、Viktor V. Khrustalyov、Yury T. Struchkov
DOI:10.1016/0040-4039(95)00287-5
日期:1995.3
Homolytic cycloaddition of dithiol 1, derived from trans-1,2-cyclohexanediol, to alkynes induced by Pr3BO2 occurs with 1,6-asymmetric induction to afford predominantly (1S∗, 6R∗, 12S∗)-trans-cyclohexano-fused 12-membered crown thialactones 4a-c. No pronounced diasteroselectivity was found in the corresponding reactions of dithiol 2, derived from cis-1,2-cyclohexanediol.