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Synthesis of Long Oxahelicenes by Polycyclization in a Flow Reactor
Author(s) -
Nejedlý Jindřich,
Šámal Michal,
Rybáček Jiří,
Tobrmanová Miroslava,
Szydlo Florence,
Coudret Christophe,
Neumeier Maria,
Vacek Jaroslav,
Vacek Chocholoušová Jana,
Buděšínský Miloš,
Šaman David,
Bednárová Lucie,
Sieger Ladislav,
Stará Irena G.,
Starý Ivo
Publication year - 2017
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201700341
Subject(s) - process engineering , engineering
A series of oxahelicenes composed of ortho / meta ‐annulated benzene/pyridine and 2 H ‐pyran rings were synthesized on the basis of the cobalt(I)‐mediated (or rhodium(I)‐ or nickel(0)‐mediated) double, triple, or quadruple [2+2+2] cycloisomerization of branched aromatic hexa‐, nona‐, or dodecaynes, thus allowing the construction of 6, 9, or 12 rings in a single operation. The use of a flow reactor was found to be beneficial for the multicyclization reactions. The stereogenic centers present in some of the oligoynes steered the helical folding in such a way that the final oxa[9]‐, [13]‐, [17]‐ and [19]helicenes were obtained in both enantiomerically and diastereomerically pure form. Specifically, the oxa[19]helicenes beat the current record in the length of a helicene backbone. Single‐molecule conductivity was studied by the mechanically controllable break‐junction method with a pyridooxa[9]helicene.