Spacer-Controlled Multiple Functionalization of Fullerenes

Abstract

The chapter provides a survey of the development and applications of the tether- and template-directed regio- and, in the occurrence, stereoselective multifunctionalization of fullerenes over the past ten years. After a presentation of the first tether-directed remote functionalization of C₆₀, a broad spectrum of applications is reviewed according to the involved reaction types. The most frequently used chemistry consists of additions of tethered 2-halomalonates (double Bingel reactions) and 1,3-dienes (double Diels-Alder reactions). The former, in particular, were used for the only known tether-directed functionalization of a higher fullerene (C₇₀) and also for most of the rare examples of three- and fourfold one-pot tether-directed derivatizations of C₆₀. Other, commonly used reactions are [3+2] cycloadditions, notably of azides and, in a few cases, of vinylcarbenes, and azomethine ylides. Some interesting examples of intramolecular [2+2] cycloadditions between fullerene moieties are also included as they are in fact spacer-controlled dimerizations of the carbon spheres. Throughout the account, particular emphasis is put on the diastereoselective generation of chiral fullerene functionalization patterns by use of enantiomerically pure tethers. As compared to tether-directed multiple additions to fullerenes, regioselective functionalizations with non-covalent templates have remained rather rare. Two important examples are reported, one involving a reversible reaction with 9,10-dimethylanthracene in solution, the other one a topochemical anthracene transfer.