Cationic cyclization of 2-alkenyl-1,3-dithiolanes: DiastereoselectiveSynthesis of trans-decalins
2011 (English)In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 76, no 9, 3274-3285 p.Article in journal (Refereed) Published
An unprecedented and highly diastereoselective 6-endo-trig cyclization of 2-alkenyl-1,3-dithiolanes has beendeveloped yielding trans-decalins, an important scaffold present in numerous di- and triterpenes. The novelty of this 6-endo-trigc yclization stands in the stepwise mechanism involving 2-alkenyl-1,3-dithiolane, acting as a novel latent initiator. It is suggested that the thioketal opens temporarily under the influence of TMSOTf, triggering the cationic 6-endo-trig cyclization, andcloses after C−C bond formation and diastereoselective protonation to terminate the process. DFT calculations confirm this mechanistic proposal and provide a rationale for the observed diastereoselectivity. The reaction tolerates a wide range of functionalities and nucleophilic partners within the substrate. We have also shown that the one-pot 6-endo-trig cyclization followedby in situ 1,3-dithiolane deprotection afford directly the corresponding ketone. This improvement allowed the achievement of the shortest total synthesis of triptophenolide and the shortest formal synthesis of triptolide.
Place, publisher, year, edition, pages
American Chemical Society , 2011. Vol. 76, no 9, 3274-3285 p.
IdentifiersURN: urn:nbn:se:su:diva-59923DOI: 10.1021/jo2001116OAI: oai:DiVA.org:su-59923DiVA: diva2:432148
FunderSwedish Research Council