New interesting molecular topologies by way of modern cross-coupling reactions*
Armin de Meijere1, Baldur Stulgies1, Karsten Albrecht1, Karsten Rauch1, Hermann A. Wegner1, Henning Hopf2, Lawrence T. Scott3, Lior Eshdat4, Ivan Aprahamian4, and Mordecai Rabinovitz4
1Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstrasse 2, 37077 Göttingen, Germany; 2Institut für Organische Chemie, Technische Universität Braunschweig, Hagenring 30, 38106 Braunschweig, Germany; 3Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, MA 02467-3860, USA; 4Department of Organic Chemistry, The Hebrew University of Jerusalem, Givat Ram, Jerusalem, 91904, Israel
Abstract: Modern transition-metal-catalyzed cross-coupling reactions, especially of the Kumada, Heck, and Suzuki types, have provided facile access to various bridge-annelated [2.2]paracyclophane derivatives including trifoliaphane and its tribenzo analog. The reduction of trifoliaphane with potassium metal in [D8]-THF led to hexakis[p-benzyl]benzene anion, which could efficiently be trapped with various electrophiles. Highly efficient multifold Suzuki couplings were performed with hexabromobenzene, octabromonaphthalene, and hexabromotriphenylene. The obtained hexa- and octaalkenylarene derivatives disclose interesting molecular shapes. Eventually, a newly developed cascade coupling of bromoarenes containing peri-positioned C-H bonds has led to indeno-annelated polycyclic aromatic hydrocarbons including indenocorannulene as well as the tetrakis- and tris(tert-butylindeno)pyrene which disclose very interesting spectroscopic properties. In particular, tetrakis(tert-butylindeno)pyrene self-assembles in solution by way of π-stacking, and it can be reduced with potassium metal to a stable dianion, a readily dimerizing trianion radical, and a tetraanion.
Keywords: [2.2]paracyclophanes; palladium catalysis; cross-couplings; hexaalkenylbenzenes; carbanions.
*Paper based on a presentation at the 11th International Symposium on Novel Aromatic Compounds (ISNA-11), St. John's, Newfoundland, Canada, 14-18 August 2005. Other presentations are published in this issue, pp. 685-888..