Supramolecural Control on Product and Substrate Selectivity via Encapsulation within a Hydrogen Bonded Self-assembled Hexameric Capsule
Giorgio Strukul, Alessandro Scarso*
Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari di Venezia, Calle Larga S. Marta 2137, 30123, Venezia. alesca@unive.it
The impressive chemo, regio and stereoselectivity displayed by enzymes are the result of a large number of weak attractive intermolecular interactions as well as repulsive steric requirements operating between the substrate and the catalytic site. In the latter, recognition phenomena allow also the selective picking of the substrate among a series of similar reagents bearing same functional groups but different size. Overall enzymes control both sides of a chemical transformation, while common organometallic catalysts usually display their effects predominantly on the right side of the catalytic reaction. Hosting of organometallic catalysts within well defined porous supports led to enhancement of enantioselectivity[
1] while for catalytic systems working under homogeneous conditions, encapsulation within rigid metal-ligand tetrahedral or square bi- pyramidal assemblies allowed rate acceleration and substrate selective reactions for a series of small reagents.[
2]
Herein we report about the simple modification of the product[
3] and substrate selectivity properties
of an organometallic catalyst via encapsulation in a spherical hexameric self-assembled capsule
held together by a seam of sixty hydrogen bonds. The steric requirements imparted by the capsule
modify product distribution in alkyne hydration reaction towards uncommon species and, at the
same time, steer substrate selectivity in parallel competitive experiments towards the substrate that
better fits the residual space available in the cavity.
1
[] Thomas, J.M.; Raja, R.; Acc. Chem. Res. 2008, 41, 708.
2
[] Leung, D. H.; Bergman, R. G.; Raymond, K. N. J. Am. Chem. Soc. 2007, 129, 2746.
3
