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.
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.