Molecular Compasses and Gyroscopes. II. Synthesis and Characterization of Molecular Rotors with Axially Substituted Bis[2-(9-triptycyl)ethynyl]arenes
作者:Carlos E. Godinez、Gerardo Zepeda、Miguel A. Garcia-Garibay
DOI:10.1021/ja012550i
日期:2002.5.1
We have developed a simple convergent procedure for the synthesis of molecular rotors consisting of a central aromatic group coupled with two axially positioned ethynyltriptycenes. Molecular rotors with 1,4-phenylene (1), 1,4'-1,1'-biphenylene (2), 9,10-anthracenylene (3), and 2,7-pyrenylene (4) groups were prepared by Pd(0)-catalyzed coupling of ethynyl triptycenes with the corresponding dibromoarenes
We describe a powerful, broadly applicable cross-coupling protocol that enables carbon–carbon bondformation at highly sterically hindered carbon centers (both sp2 and sp3) by employing organocopper reagents under palladium catalysis. Experimental studies and theoretical calculations indicated that the key to the unique reactivity of copper is the relatively low activation energy of the compact transmetalation