Simple Modification in Hexakis-Addition for Efficient Synthesis of C₆₀-Centered Dendritic Molecules Bearing Multiple Aromatic Chromophores

Abstract

In the templated hexakis-addition reaction of malonic esters with C(60) to prepare dendritic macromolecules that are terminated symmetrically with 12 derivatized pyrenes, a simple modification to use a much larger excess of the bromination agent resulted in dramatic increases in the product yields. [structure: see text]

Formation of Highly Charged Quasi‐Molecular Ions of a Polycationic [60]Fullerene Hexakis‐Adduct and Their Fragmentation Behavior in the Gas Phase

“…The initial concepts for the synthesis of T h -symmetrical hexakis-adducts of C 60 that we previously developed [8][9][10] and were later modified by other groups [15,16] turned out to be inefficient for the synthesis of the dodeca-cationic target molecule 1. The quaternization leading to the formation of the desired pyridinium had to be the final step because chromatographic purification on silica of such highly polar and water-soluble adducts is impossible.…”

Efficient Synthesis of C2v‐Symmetrical Pentakisadducts of C60 as Versatile Building Blocks for Fullerene Architectures that Involve a Mixed Octahedral Addition Pattern

“…[15] To investigate the potential of isoxazolines to serve as a protective group in the synthesis of fullerene pentakisadducts, we targeted the synthesis of mixed [5:1]hexakisadduct 1 c (Scheme 1), which bears ten acid-labile tert-butyl-protected carboxylic groups. Fivefold cyclopropanation with bis[3-(tert-butoxycarbonyl)propyl] malonate [18] was achieved by using the modified reaction conditions for the synthesis of fullerene hexakisadducts [19,20] in 42 % yield. However, heating 1 c to 130 8C in o-dichlorobenzene with a 30-fold excess amount of maleic anhydride yielded 3 c in only around 70 % (HPLC) after three days; at 140 8C decomposition of the product was already predominant.…”

Di‐ and Dodeca‐Mitsunobu Reactions on C60 Derivatives: Post‐Functionalization of Fullerene Mono‐ and Hexakis‐Adducts

“…[5] In the aforementioned contexts, the relatively stable methanofullerene adducts obtained through Bingel cyclopropanation reactions are of particular interest. However, this functionalization approach-primarily developed by A. Hirsch [6] and later optimized by Y.-P. Sun [7] -suffers from two critical weaknesses. One is its effectively exclusive limitation to malonates; only a few exceptions are known.…”

“…Hexakis-adduct 3 was then readily synthesized by using the optimized conditions described by Y.-P. Sun. [7] The resulting crude mixture was purified on silica-gel column to afford an inseparable mixture of pentakis-and hexakis-adduct. The mixture of both isomers was subjected to desilylation using an excess of hydrogen chloride as a methanolic solution.…”

“…In contrast, for hexakis-adduct 4, the core is completely shielded by the malonates and cannot react anymore. No reaction took place with known Mitsunobu substrates 4-methyl-N-(prop-2-ynyl)benzenesulfonamide and isoindoline-1,3-dione (entries 6,7).…”