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7664848 
Journal Article 
Efficient helicene synthesis: Friedel-Crafts-type cyclization of 1,1-difluoro-1-alkenes 
Ichikawa, J; Yokota, M; Kudo, T; Umezaki, S; , 
2008 
Yes 
Angewandte Chemie (International Edition)
ISSN: 1433-7851
EISSN: 1521-3773 
WILEY-V C H VERLAG GMBH 
WEINHEIM 
47 
26 
4870-4873 
English 
18506861 
WOS:000257040800015 
(Chemical Equation Presented) The unique properties of fluorine substituents, leaving groups that also stabilize an a 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). © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.