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Cyclotrimerization of Corannulyne: Steric Hindrance Tunes the Inversion Barriers of Corannulene Bowls
Author(s) -
Yanney Michael,
Fronczek Frank R.,
Henry William P.,
Beard Debbie J.,
Sygula Andrzej
Publication year - 2011
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201101374
Subject(s) - corannulene , chemistry , pseudorotation , steric effects , molecule , crystallography , trifluoromethanesulfonate , computational chemistry , stereochemistry , catalysis , organic chemistry
Abstract Palladium‐catalyzed cyclotrimerization of corannulyne generated from 2‐trimethylsilylcorannulenyl triflate produced a C 60 H 24 hydrocarbon that prefers a highly nonplanar “twist” conformation of C 1 symmetry, as demonstrated by X‐ray crystal structure determination and HDFT calculations. Its three corannulene subunits, identical in the idealized D 3 h symmetry, exhibit dramatically different inversion barriers (from 8.4 to 17.3 kcal mol –1 ), tuned by the steric congestion inside the highly dissymmetric structure. Bowl‐to‐bowl inversion of the corannulene unit with the lowest activation barrier results in pseudorotation of the molecule and gives rise to a 1 H NMR spectrum exhibiting only 12 distinct proton signals. The line‐shape analysis of selected NMR signals gave an estimation of the barrier at 8.5–8.6 kcal mol –1 .