Switchable pyrrole-based hydrogen bonding motif in enantioselective trifunctional organocatalysis

Pyrroles are versatile chemical motifs for molecular recognition or ligand design but their utility as catalytic components are underexplored. We incorporated a pyrrole motif into our acid-switchable, MAP-based trifunctional organocatalytic system. The switching-on of this system by an external Bronsted acid, 3-methyl benzoic acid, presented proficient catalysis in both aza-Morita-Baylis-Hillman (MBH, up to >95% conversion and 88% ee over 3 h) and MBH (up to 81% conversion and 77% ee over 6 h) reactions. The enhanced catalytic generality and proficiency may be due to the new cooperativity via CH/pi interactions between pyrrole and the acid switch. (C) 2018 Elsevier Ltd. All rights reserved.