Quaternary Ammonium, Phosphonium, and Tertiary Sulfonium Salts as Hydrogen‐Bonding Catalysts

The Wittig olefination reaction and modifications involving phosphoryl-stabilized carbanions. Stereochemistry, mechanism, and selected synthetic aspects

Small-molecule H-bond donors in asymmetric catalysis.

Dimethyloxosulfonium Methylide ((CH3)2SOCH2) and Dimethylsulfonium Methylide ((CH3)2SCH2). Formation and Application to Organic Synthesis

The metal (ion)-free catalysis of organic reactions is a contemporary challenge that is just being taken up by chemists. Hence, this field is in its infancy and is briefly reviewed here, along with some rough guidelines and concepts for further catalyst development. Catalysis through explicit hydrogen bonding interactions offers attractive alternatives to metal (ion)-catalyzed reactions by combining supramolecular recognition with chemical transformations in an environmentally benign fashion. Although the catalytic rate accelerations relative to uncatalyzed reactions are often considerably less than for the metal (ion)-catalyzed variants, this need not be a disadvantage. Also, owing to weaker enthalpic binding interactions, product inhibition is rarely a problem and hydrogen bond additives are truly catalytic, even in water.

Metal-free organocatalysis through explicit hydrogen bonding interactions

Charged intermediates and reagents are ubiquitous in organic transformations. The interaction of these ionic species with chiral neutral, anionic, or cationic small molecules has emerged as a powerful strategy for catalytic, enantioselective synthesis. This review describes developments in the burgeoning field of asymmetric ion-pairing catalysis with an emphasis on the insights that have been gleaned into the structural and mechanistic features that contribute to high asymmetric induction.

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Quaternary Ammonium, Phosphonium, and Tertiary Sulfonium Salts as Hydrogen‐Bonding Catalysts

References

The Wittig olefination reaction and modifications involving phosphoryl-stabilized carbanions. Stereochemistry, mechanism, and selected synthetic aspects

Small-molecule H-bond donors in asymmetric catalysis.

Dimethyloxosulfonium Methylide ((CH3)2SOCH2) and Dimethylsulfonium Methylide ((CH3)2SCH2). Formation and Application to Organic Synthesis

Metal-free organocatalysis through explicit hydrogen bonding interactions

Asymmetric ion-pairing catalysis.