Dibenzylammonium trifluoroacetate

In 2004, List reported that several ammonium salts including dibenzylammonium trifluoroacetate catalyzed the chemoselective 1,4 reduction of a, 5-unsaturated aldehydes with Hantszch esters as hydride sources [40]. It is assumed that substrate activation via iminium ion formation results in selective 1,4 addition of hydride. Subsequently, List [41] and MacMillan [42] reported asymmetric versions of this reaction promoted by chiral imidazoUdinone salts. In this context, several reports of this metal-free reductive process catalyzed by chiral phosphoric acids have appeared in the recent literature. 

Dibenzylammonium trifluoroacetate. Mol. wt. 311.31 m.p. 139°. This salt is obtained in 78% yield by reaction of trifluoroacetic acid and dibenzylamine in ether at room temperature for 30 minutes. 

Pentanediol is often superior to other diols such as 2,3-butanediol for these reactions because of higher distereoselectivities in reactions with nucleophiles and the more facile cleavage of the resulting hydroxy ether by oxidation-p-elimination. Removal of the chiral auxiliary is usually carried out with Pyri-dinium Chlorochromate oxidation followed by p-elimination using KOH, K2CO3, piperidinium acetate, dibenzylammonium trifluoroacetate, " or DBU. In some cases, 1,3-butanediol is preferred because the final 3-elimination may be effected under milder conditions. ... 

In connection with a total synthesis of gibberellic acid, Corey and coworkers used dibenzylammonium trifluoroacetate to accomplish a regioselective aldol condensation (equation 99)." The success of this... 

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