Brønsted Acid-Promoted Cyclizations of Siloxyalkynes with Arenes and Alkenes
Liming Zhang and Sergey A. Kozmin*
*Department of Chemistry, University of Chicago, 5735 South Ellis Avenue,
Chicago, Illinois 60637, Email: skozmin
uchicago.edu
L. Zhang, S. A. Kozmin, J. Am. Chem. Soc., 2004, 126, 10204-10205.
DOI: 10.1021/ja046586x
see article for more reactions
Abstract
Brønsted acid-mediated cyclizations of siloxyalkynes with simple arenes and alkenes afforded substituted tetralone and cyclohexenone derivatives. A wide range of substrates can be employed in these carbocyclizations.
see article for more examples
Details
This document reports the first Brønsted acid-mediated cyclizations of siloxyalkynes with simple arenes and alkenes, leading to substituted tetralone and cyclohexenone derivatives. The process involves generating a highly electrophilic ketenium ion from siloxyalkyne, which is then trapped by a nucleophile. Various catalysts were tested, with HNTf2 (trifluoromethanesulfonimide) proving most effective, yielding silyl enol ether efficiently. The reaction mechanism suggests an electrophilic aromatic substitution, supported by experiments with enantiomerically enriched alkynes. The study also explored enyne cyclizations, finding that a stoichiometric amount of HNTf2 is required for efficient carbocyclization. The research highlights the unique reactivity of siloxyalkynes and the importance of the NTf2- anion in facilitating the formation and interception of reactive intermediates. The findings open new avenues for synthesizing carbocyclic and heterocyclic compounds without needing electron-rich arenes and alkenes. The work was supported by various foundations and awards, with detailed experimental procedures and compound characterizations available online.
Key Words
ID: J48-Y2004-1680
