Organocatalysis by bimacrocyclic NHCs: unexpected formation of a cyclic hemiacetal instead of a gamma-butyrolactone.
Two bimacrocyclic imidazolinium salts of different size, precursors to respective NHCs (N-heterocyclic carbenes), were tested as precatalysts in the reaction of aromatic aldehydes or ketones with enals. The expected lactones were produced in most cases, but in the reaction of methyl 4-formylbenzoate with cinnamaldehyde, the larger bimacrocycle led to the formation of a cyclic hemiacetal, while the smaller bimacrocycle gave the anticipated lactone.
Winkelmann
Ole
O
Otto-Diels-Institut für Organische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstr. 40, D-24098, Kiel, Germany.
Näther
Christian
C
Lüning
Ulrich
U