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Mukaiyama–Michael Reactions with trans ‐2,5‐Diarylpyrrolidine Catalysts: Enantioselectivity Arises from Attractive Noncovalent Interactions, Not from Steric Hindrance
Author(s) -
Kemppainen Eeva K.,
Sahoo Gokarneswar,
Piisola Antti,
Hamza Andrea,
Kótai Bianka,
Pápai Imre,
Pihko Petri M.
Publication year - 2014
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.201304240
Subject(s) - steric effects , enantioselective synthesis , chemistry , non covalent interactions , catalysis , intermolecular force , stereoselectivity , organocatalysis , transition state , computational chemistry , stereochemistry , organic chemistry , hydrogen bond , molecule
The scope of the enantioselective Mukaiyama–Michael reactions catalyzed by trans‐ 2,5‐diphenylpyrrolidine has been expanded to include both α‐ and β‐substituted enals. However, the rationalization of the observed enantioselectivity is far from obvious since the catalyst is not very sterically hindered. DFT calculations were carried out to rationalize the observed stereoselectivities. Transition states of the CC bond formation between iminium intermediates and silyloxyfurans were located and their relative energies were used to estimate the stereoselectivity data. We find excellent agreement between the predicted and observed stereoselectivities. The analysis of intermolecular forces reveals that the enantioselectivity is mostly due to stabilizing noncovalent interactions between the reacting partners, not due to steric hindrance. The role of attractive noncovalent interactions in enantioselective catalysis may be underappreciated.