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Regioselective Intramolecular Pauson–Khand Reactions of C 60 : An Electrochemical Study and Theoretical Underpinning
Author(s) -
Martín Nazario,
Altable Margarita,
Filippone Salvatore,
MartínDomenech Ángel,
Poater Albert,
Solà Miquel
Publication year - 2005
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200401200
Subject(s) - chemistry , regioselectivity , intramolecular force , cyclopentenone , enyne , alkyne , reactivity (psychology) , pyrrolidine , cycloaddition , pauson–khand reaction , stereochemistry , alkene , organic chemistry , catalysis , medicine , alternative medicine , pathology
Suitably functionalized fulleropyrrolidines endowed with one or two propargyl groups at the C‐2 position of the pyrrolidine ring (1,6‐enynes) react efficiently and regioselectively with [Co 2 (CO) 8 ] to afford the respective Pauson–Khand products with an unprecedented three ( 5 a – d , 7 , and 24 ) or five ( 25 ) pentagonal rings, respectively, fused onto the fullerene sphere. Fulleropyrrolidines with 1,7‐, 1,9‐, 1,10‐, or 1,11‐enyne moieties do not undergo the PK reaction and, instead, the intermediate dicobalt complexes formed with the alkynyl group are isolated in quantitative yields. These differences in reactivity have been studied by DFT calculations with a generalized gradient approximation (GGA) functional and several important energy and structural differences were found for the intermediates formed by the interaction between the coordinatively unsaturated Co atom and the π system of C 60 in 1,6‐ and 1,7‐enynes. The different lengths of the alkyne chains are responsible for the observed reactivities. Cyclic voltammetry reveals that the presence of the cyclopentenone's carbonyl group connected directly to the C 60 core results in PK compounds with remarkable electron‐accepting ability.