- Prato reaction
The Prato reaction in
fullerene chemistry describes the functionalization offullerene s andnanotube s withazomethine ylide s in a1,3-dipolar cycloaddition . [cite journal | author = M. Maggini, G. Scorrano and M. Prato | title = Addition of azomethine ylides to C60: synthesis, characterization, and functionalization of fullerene pyrrolidines | year = 1993 | journal =J. Am. Chem. Soc. | volume = 115 | issue = 21 | pages = 9798–9799 | doi = 10.1021/ja00074a056] The amino acidsarcosine reacts withparaformaldehyde when heated atreflux intoluene to anylide which reacts with a double in a 6,6 ring position in afullerene in a1,3-dipolar cycloaddition to yield a N-methylpyrrolidine derivative or pyrrolidinofullerene or pyrrolidino [60] fullerene in 82% yield.This method is also used in the functionalization of single wall
nanotube s [cite journal | author = V. Georgakilas, K. Kordatos, M. Prato, D. M. Guldi, M. Holzinger and A. Hirsch | title = Organic Functionalization of Carbon Nanotubes | year = 2002 | journal =J. Am. Chem. Soc. | volume = 124 | issue = 5 | pages = 760–761 | doi = 10.1021/ja016954m] . When the amino acid is modified with aglycine chain the resulting nanotubes are soluble in common solvents suchchloroform andacetone . Another characteristic of the treated nanotubes is their larger aggregate dimensions compared to untreated nanotubes.Just as in other fullerene reactions like the
Bingel reaction orDiels-Alder reaction s this reaction can be reversed. A thermalretro-cycloaddition of a pyrrolidinofullerene with a strongdipolarophile such asmaleic acid and acatalyst such asWilkinson's catalyst orcopper triflate in 1,2-dichlorobenzene atreflux 8 to 18 hours regenerates the pristine C60 fullerene [cite journal | author = N. Martín, M. Altable, S. Filippone, A. Martín-Domenech, L. Echegoyen and C. M. Cardona | title = Retro-Cycloaddition Reaction of Pyrrolidinofullerenes | year = 2006 | journal =Angewandte Chemie International Edition | volume = 45 | issue = 1 | pages = 110–114 | doi = 10.1002/anie.200502556] . The dipolarophile is required in a 30 fold excess and traps theylide driving the reaction to completion. The N-methyl-pyrrolidine derivative reacts poorly (5% yield) and for a successful reaction the nitrogen ring also requires substitution in the α-position withmethyl ,phenyl orcarboxylic ester groups.In an alternative method a
nanotube addition is performed with theN-oxide oftrimethylamine and LDA [cite journal | author = C. Menard-Moyon, N. Izard, E. Doris and C. Mioskowski | title = Separation of Semiconducting from Metallic Carbon Nanotubes by Selective Functionalization with Azomethine Ylides | year = 2006 | journal =J. Am. Chem. Soc. | volume = 128 | issue = 20 | pages = 6552–6553 | doi=10.1021/ja060802f] at reflux intetrahydrofuran with an efficiency of 1 functional group in 16 nanotube carbon atoms. When the amine also carries an aromatic group such aspyrene the reaction takes place even atroom temperature because this group preorganizes itself to the nanotube surface prior to reaction bypi stacking .In one application a liquid fullerene is obtained when the pyrrolidone substituent is a 2,4,6-tris(alkyloxy)phenyl group [cite journal | author = T. Michinobu, T. Nakanishi, J. P. Hill, M. Funahashi and K. Ariga | title = Room Temperature Liquid Fullerenes: An Uncommon Morphology of C60 Derivatives | year = 2006 | journal =
J. Am. Chem. Soc. | volume = 128 | issue = 32 | pages = 10384–10385 | doi = 10.1021/ja063866z] although a small amount of solvent is still required.References
External links
*
Wikimedia Foundation. 2010.