Tris(2,2,2-trifluoroethyl) borate, also commonly referred to as the Sheppard amidation reagent,
is a chemical compound with the formula . This
borate ester reagent is used in organic synthesis.
Preparation
Tris(2,2,2-trifluoroethyl) borate can be prepared by reaction of
trifluoroethanol with
boron trichloride,
borane dimethylsulfide,
boron tribromide, or
boric anhydride. The latter is more convenient for larger scale preparations due to its low cost and ease of handling.
:
The product is purified by distillation.
Applications
The reagent is mostly used in
condensation reactions. It has been shown to promote the direct formation of
amides
from
carboxylic acid
In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an Substituent, R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl ...
s and
amines as well as the formation of
imines from amines or amides with
carbonyl compounds.
It has also been used for the
coupling of unprotected
amino acid
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...
s with amines.
It has also been shown to mediate
formylation of amines, via
transamidation of
dimethylformamide.
It is a strong
Lewis acid (
acceptor number = 66,
Gutmann-Beckett method).
[Beckett, Michael A; Rugen-Hankey Martin P; Strickland, Gary C; Varma, K. Sukumar, ''Lewis acidity in haloalkyl orthoborate and metaborate esters'', (2001) ''Phosphorus, Sulfur, and Silicon'', 168, 437-440.]
References
Further reading
* Related reagent tris(2,2,2-trinitroethyl)borate: {{cite journal , doi = 10.1039/c4cc04616a, pmid = 25012058, title = Improved green-light-emitting pyrotechnic formulations based on tris(2,2,2-trinitroethyl)borate and boron carbide, journal = Chem. Commun., volume = 50, issue = 67, pages = 9581–9583, year = 2014, last1 = Klapötke, first1 = Thomas M., last2 = Krumm, first2 = Burkhard, last3 = Rusan, first3 = Magdalena, last4 = Sabatini, first4 = Jesse J., doi-access = free
Borate esters
Organofluorides
Trifluoromethyl compounds