Edge Article
Chemical Science
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At lower catalyst loading (1 mol%) higher TON can be
reached when the reaction is carried out at 50 ꢁC. The TON (mol
product/mol Cu) of the reaction was 94 (24 h, 94% yield, see
Table S5†) when the reaction is carried out in the presence of
the nanoconcentrator, which is almost 2.5 times higher than
the TON when XantphosCu(I) is used under the same reaction
conditions (24 h, 37% yield, see Table S5†). This again clearly
demonstrates the effect of catalyst pre-organization for reac-
tions that proceed via a dinuclear pathway.
Conclusions
In this contribution, we unraveled the mechanism of the Cu(I)
(Xantphos) catalyzed cyclization of 4-pentynoic acid to the cor-
responding enol lactone. The reaction involves a bimetallic
activation of the substrate, explaining why this type of reaction
needs relatively high catalyst loading. Interestingly, pre-
organization of copper catalysts based on SXanthphos (a
sulfonated analogue) in a guanidinium functionalized M12L24
nanosphere leads to high local concentrations of catalysts and
as a result improved reaction rates even when the average
catalyst concentration is low. Having demonstrated that this
supramolecular strategy facilitates reactions that proceed via
dinuclear Cu(I) complexes, we can now extend these catalyst
design strategies to related reactions based on abundant tran-
sition metals.
´
´
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There are no conicts to declare.
Acknowledgements
Financial support was provided by the University of Amsterdam
and by the European Research Council (ERC Advanced Grant
339786-NAT_CAT).
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