Alcohols, Phenols and Carboxylic Acids as Asymmetric Organocatalysts

Alcohols, Phenols and Carboxylic Acids as Asymmetric Organocatalysts 

The activation of electrophiles by means of Bronsted acids is a central topic in organic chemistry as it allows the energy of the lowest unoccupied molecular orbital to be reduced, activating the electrophile towards a nucleophilic attack. This behaviour explains why many organic reactions of carbonyl compounds are performed in the presence of catalytic amounts of strong protic acids. 

Sustainable Catalysis Without Metals or Other Endangered Elements, Part 2 Edited by Michael North 

Since the formation of a hydrogen bond can also be considered a stage of a proton-transfer reaction, accordingly there is an equilibrium between the hydrogen-bonding complex and ion pair, so this classiftcation is not always easy to do. 

It seems appropriate to remember that there are also other classes of molecules that are catalytically active thanks to one of the mentioned mechanisms (ureas, thioureas, phosphoric acids, etc.) as well as molecules with two or more different functional sites (bifunctional organocatalysts) one of which is often an alcoholic/phenolic/carbojqrlic group (amino-alcohols, aminoacids, proline derivatives, aminophenols, etc.) they will be not discussed in this chapter because they have already been examined in previous chapters or because they contain nonsustainable elements. 

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