Hydrogen Bonding and Internal or External Lewis or Brønsted Acid Assisted (Thio)urea Catalysts

• Published in: European journal of organic chemistry Vol. 2020; no. 9; pp. 1057 - 1068
• Main Authors: Gimeno, M. Concepción, Herrera, Raquel P.
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 08.03.2020
• Subjects: (Thio)urea; Activation; Brønsted acid; Catalysis; Catalysts; Hydrogen bonding; Hydrogen bonds; Lewis acid; Ureas
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.201901344

The obtainment of more active organocatalysts has promoted the search for new modes of activation and new organocatalytic systems. Inspired on the mode of activation of enzymes, organocatalysis has recently focused on the challenge to create an enzyme‐like “active site” giving access to hydrogen‐bond donors (HBDs) with enhanced activity. Therefore, the assembly of catalytic species, connected through multiple weak inter‐ or intramolecular interactions, is a young and emerging topic of research which could become in the future a powerful tool for asymmetric catalysis. In the area of (thio)ureas, different alternatives such as internal hydrogen bonds or the use of an internal or an external Lewis or Brønsted acid assisted catalysts have been developed. The pivotal publications recently reported covering this family of organocatalysts are proof of this importance. This review treats to illustrate these important and scarce examples and to show a plausible mode of activation for each one. During last years, the assembly of catalytic species connected through multiple weak inter‐ or intramolecular interactions (using hydrogen bonds, Lewis of Brønsted acids) has enhanced the ability of hydrogen bond‐based catalysts such as (thio)ureas.