Cationic cyclization of keto-epoxides mediated by zirconium(IV) tetrachloride: diastereoselective synthesis of cis-decalinols
摘要:
10-Methyl-cis-9-decalinols are important motifs in several natural products and key intermediates in total synthesis. Herein, we wish to describe a highly chemo- and diastereoselective cyclization of ketoepoxides leading to 10-methyl-cis-9-decalinols. This method based on the use of zirconium(IV) tetrachloride permits the access to a wide variety of cis-decalinols in good to excellent yields. The cationic cyclization could also be performed with chiral keto-epoxide with complete control of the diastereoselectivity affording cis-bicyclic tertiary alcohol with good enantiomeric excess. The chemo- and the diastereoselectivity are assumed to result from the ability of Zr(IV) to generate highly stable bidentic complexes with alpha-hydroxy-ketone intermediates. (C) 2011 Elsevier Ltd. All rights reserved.
TMSOTf, triggering the cationic 6-endo-trig cyclization, and closes 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
10-Methyl-cis-9-decalinols are important motifs in several natural products and key intermediates in total synthesis. Herein, we wish to describe a highly chemo- and diastereoselective cyclization of ketoepoxides leading to 10-methyl-cis-9-decalinols. This method based on the use of zirconium(IV) tetrachloride permits the access to a wide variety of cis-decalinols in good to excellent yields. The cationic cyclization could also be performed with chiral keto-epoxide with complete control of the diastereoselectivity affording cis-bicyclic tertiary alcohol with good enantiomeric excess. The chemo- and the diastereoselectivity are assumed to result from the ability of Zr(IV) to generate highly stable bidentic complexes with alpha-hydroxy-ketone intermediates. (C) 2011 Elsevier Ltd. All rights reserved.