Efficient Helicene Synthesis: Friedel–Crafts‐type Cyclization of 1,1‐Difluoro‐1‐alkenes

Abstract

The unique properties of fluorine substituents, leaving groups that also stabilize an α carbocation, are exploited in a high-yielding synthesis of substituted [4]- to [6]helicenes in three or four steps from commercially available compounds: Two fused benzene rings are constructed in the title reaction of readily prepared 1,1-difluoro-1-alkenes containing two aryl groups followed by dehydrogenation (see scheme). Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2008/z801396_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.