Stereoselective Free Radical Cycloaddition-macrocyclization in Facile Synthesis of trans-cyclohexano-fused 12-membered Crown Thioethers
Homolytic cycloaddition of dithiols 1,2 derived from trans- and eis-1,2-cyclohexanediols to alkynes, induced by Pr3B-O2, 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 on molecular mechanics calculations the stereoselectivity is rationalized as a result of entropy favored pathway of macrocyclization.
Troyansky, Emmanuil I.; Ismagilov, Rustem F.; Samoshin, Vyacheslav V.; Strelenko, Yury A.; Demchuk, Dmitry V.; Nikishin, Gennady I.; Lindeman, Sergey V.; Khrustalyov, Viktor N.; and Struchkov, Yury T., "Stereoselective Free Radical Cycloaddition-macrocyclization in Facile Synthesis of trans-cyclohexano-fused 12-membered Crown Thioethers" (1995). Chemistry Faculty Research and Publications. 640.