Gold-Catalyzed Regiospecific Annulation of Unsymmetrically Substituted 1,5-Diynes for the Precise Synthesis of Bispentalenes |
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Authors: | Sara Tavakkolifard Dr Kohei Sekine Lisa Reichert Mina Ebrahimi Ketevan Museridz Elena Michel Dr Frank Rominger Rasool Babaahmadi Prof Alireza Ariafard Prof Brian F Yates Dr Matthias Rudolph Prof?Dr A Stephen K Hashmi |
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Institution: | 1. Organisch-Chemisches Institut, Heidelberg University, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
These authors contributed equally to this work.;2. Organisch-Chemisches Institut, Heidelberg University, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany;3. School of Physical Sciences (Chemistry), University of Tasmania, Private Bag 75, Hobart, TAS, 7001 Australia |
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Abstract: | Precise control of the selectivity in organic synthesis is important to access the desired molecules. We demonstrate a regiospecific annulation of unsymmetrically substituted 1,2-di(arylethynyl)benzene derivatives for a geometry-controlled synthesis of linear bispentalenes, which is one of the promising structures for material science. A gold-catalyzed annulation of unsymmetrically substituted 1,2-di(arylethynyl)benzene could produce two isomeric pentalenes, but both electronic and steric effects on the aromatics at the terminal position of the alkyne prove to be crucial for the selectivity; especially a regiospecific annulation was achieved with sterically blocked substituents; namely, 2,4,6-trimetyl benzene or 2,4-dimethyl benzene. This approach enables the geometrically controlled synthesis of linear bispentalenes from 1,2,4,5-tetraethynylbenzene or 2,3,6,7-tetraethynylnaphthalene. Moreover, the annulation of a series of tetraynes with a different substitution pattern regioselectively provided the bispentalene scaffolds. A computational study revealed that this is the result of a kinetic control induced by the bulky NHC ligands. |
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Keywords: | gold homogeneous catalysis pentalenes polycyclic aromatic hydrocarbons regiospecific |
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