Donor–Acceptor Cyclopropanes as Three‐Carbon Components in a [4+3] Cycloaddition Reaction with 1,3‐Diphenylisobenzofuran

Dienophiles with a difference: 2-Aryl 1,1-bis(alkoxycarbonyl) cyclopropanes undergo the title reaction under the catalysis of ytterbium triflate (Yb(OTf)3) in excellent yield (see scheme). Under mild reaction conditions, the major product is the less stable exo isomer. At higher temperatures, the endo isomer is obtained exclusively, as the exo cycloadduct decomposes through cycloreversion. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2008/z704438_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.