Collect. Czech. Chem. Commun. 2011, 76, 2005-2022
Published online 2012-02-02 12:09:31

Enantioselective [2+2+2] cycloisomerisation of alkynes in the synthesis of helicenes: The search for effective chiral ligands

Irena G. Staráa,*, Angelina Andronovaa, Adrian Kollároviča, Štěpán Vyskočilb, Sylvain Jugéc, Guy C. Lloyd-Jonesd, Patrick J. Guirye and Ivo Starýa,*

a Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nám. 2, 166 10 Prague 6, Czech Republic
b Department of Organic Chemistry, Charles University in Prague, Albertov 2030, 128 40 Prague 2, Czech Republic
c Université de Bourgogne, UFR Sciences et Techniques, ICMU-UMR 5260, 9 Avenue Alain Savary-BP 47870, 21078 Dijon Cedex, France
d The Bristol Centre for Organometallic Catalysis and Organic & Biological Chemistry Section, School of Chemistry, University of Bristol, Cantock’s Close, Bristol, BS8 1TS, United Kingdom
e Centre for Synthesis and Chemical Biology, UCD School of Chemistry and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland


The enantioselective [2+2+2] cycloisomerisation of the aromatic triynes under nickel(0) catalysis to afford nonracemic [6]- and [7]helicene derivatives has been systematically studied. A collection of mono- and bidentate phosphines, phosphites, phosphinites and phosphinous amides possessing stereogenic units such as chiral centre, axis or plane (or their combinations) has been tested and axially chiral binaphthyl-derived monodentate MOP-type phosphine ligands were the optimal class of ligands. Nickel complexes of these ligands afforded nonracemic tetrahydro[6]helicene in up to 64% ee in a model reaction.

Keywords: Helicenes; Alkynes; Cycloisomerisation; Nickel catalysis; Phosphorus ligands; Enantioselectivity; Chirality; Asymmetric catalysis.

References: 78 live references.