Open AccessBambusurils as a mechanistic tool for probing anion effects
Author(s) -
Lucie Jašíková,
M. do L. L. Rodrigues,
Jana Lapešová,
Tomáš Lízal,
Vladimír Šindelář,
Jana Roithová
Publication year - 2019
Publication title -
faraday discussions
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.255
H-Index - 110
eISSN - 1364-5498
pISSN - 1359-6640
DOI - 10.1039/c9fd00038k
Subject(s) - chemistry , catalysis , reaction rate , alkyne , reaction mechanism , ion , photochemistry , methanol , reaction intermediate , conjugated system , rate determining step , combinatorial chemistry , inorganic chemistry , organic chemistry , polymer
Bambusuril macrocycles have high affinity towards anions (X-) such as PF6- and SbF6- or BF4- and ClO4-. Therefore, addition of bambusurils to reaction mixtures containing these anions effectively removes the free anions from the reaction process. Hence, comparing reactions with and without addition of bambusurils can demonstrate whether the anions actively participate in the reaction mechanism or not. We show this approach for gold(i) mediated addition of methanol to an alkyne. The reaction mechanism can proceed via monoaurated intermediates (e.g., in catalysis with [(IPr)AuX]) or via diaurated intermediates (e.g., in catalysis with [(PPh3)AuX]). We show that anions X- slightly affect the reaction rates, however the effect stays almost the same even after their encapsulation in the cavity of bambusurils. We also demonstrate that X- affects the overall reaction rate in the very same way as the reaction rate of the protodeauration step. All results are consistent with the indirect effect of X- by the acidity of the conjugated acid HX on the rate-determining step. There is no evidence that a direct involvement of X- would affect the reaction rate.