Amines trifluoroacetyl

Trifluoroacetamides are more stable toward nucleophiles than the corresponding esters and are easily formed from trifluoroacetic anhydride and the amine. The trifluoroacetyl group (Tfac) is slowly cleaved by aqueous or methanolic HQ, NH, or Ba(OH)2 solutions as well as by NaBHj in methanol (M.L. Wolfrom, 1967). 

TRIFLUOROACETYLATION OF AMINES AND AMINO ACIDS UNDER NEUTRAL, MILD CONDITIONS N-TRIFLUOROACET ANILIDE AND N-TRIFLUOROACETYL-l-TYROSINE... 

As for the reaction with alcohols N -trifluoroacetylbenzotriazole is conveniently used for trifluoroacetylation of primary or secondary alkyl or aryl amines to give excellent yields of trifluoroacetamides [95al... 

The reaction was second order in acid and first order in substrate, so both rearrangements and the disproportionation reaction proceed via the doubly-protonated hydrazobenzene intermediate formed in a rapid pre-equilibrium step. The nitrogen and carbon-13 kinetic isotope effects were measured to learn whether the slow step of each reaction was concerted or stepwise. The nitrogen and carbon-13 kinetic isotope effects were measured using whole-molecule isotope ratio mass spectrometry of the trifluoroacetyl derivatives of the amine products and by isotope ratio mass spectrometry on the nitrogen and carbon dioxide gases produced from the products. The carbon-12/carbon-14 isotope... 

A sensitive method for primary amines is shown in reaction 2, leading to the corresponding 7V-benzenesulfonyl-/V-trifluoroacetyl derivatives. These can be determined by GC-ECD using SE-30 columns LOD 1-5 pg, which is about 200 times more sensitive than GC-FID. The method was applied for determination of phenethylamine (33) in urine110. This analysis was performed also by LLE into n-pentane, derivatization to the benzenesulfonamide and GC-FPD using a capillary column recoveries of aliphatic primary amines in urine were 91-107%, RSD 0.2-4.5%111,112. Amines in environmental waters and sediments were determined after LLE with dichloromethane, derivatization with benzenesulfonyl chloride and GC-SIM-MS LOD 0.02-2 pg/L of water and 0.5-50 ng/g of sediment113. 

Usually alcohols accompany aldehydes in reductions with lithium aluminum hydride [1104] or sodium bis 2-methoxyethoxy)aluminum hydride [544], or in hydrogenolytic cleavage of trifluoroacetylated amines [7772]. Thus terr-butyl ester of. -(. -trifluoroacetylprolyl)leucine was cleaved on treatment with sodium borohydride in ethanol to rerr-butyl ester of A7-prolylleucine (92% yield) and trifluoroethanol [7772]. During catalytic hydrogenations over copper chromite, alcohols sometimes accompany amines that are the main products [7775]. 

Figure 25. Trace enantiomer analysis of L-aspartic acid (obtained by enzymatic amination of fumarate with L-aspartase and determined as the A -trifluoroacetyl-O-methyl ester) on i.-Chirasil-Val31 [20 mx0.25 mm (i.d.) glass capillary column, 90 CC, 0.4 bar hydrogen] with detection by GLC MS selected ion monitoring (mj 198.1) and multiscanning chromatography (MSC, 8 scans)186.

A closely related method does not require conversion of enantiomers to diastereomers but relies on the fact that (in principle, at least) enantiomers have different nmr spectra in a chiral solvent, or when mixed with a chiral molecule (in which case transient diastereomeric species may form). In such cases the peaks may be separated enough to permit the proportions of enantiomers to be determined from their intensities.145 Another variation, which gives better results in many cases, is to use an achiral solvent but with the addition of a chiral lanthanide shift reagent such as tris[3-trifluoroacetyl-d-camphorato]europium-(III).146 Lanthanide shift reagents have the property of spreading nmr peaks of compounds with which they can form coordination compounds, e.g., alcohols, carbonyl compounds, amines, etc. Chiral lanthanide shift reagents shift the peaks of the two enantiomers of many such compounds to different extents. 

The C-acyl heterocycles do not generally form hydrates under acidic or alkaline conditions unless the five-membered ring is also substituted with a second electron-withdrawing group or, as with the trifluoroacetyl and trichloroacetyl derivatives, the carbonyl group is activated to nucleophilic attack. Such activated substituents also undergo the normal reactions with aqueous sodium hydroxide, sodium alkoxide and with amines to give the appropriate... 

Reactions of enamines with monoimines of o-quinones afford polycylic compounds 228 with an oxazine ring (86MI2).Trifluoroacetylation of enamines with trifluoroacetic acid takes place in the /3-position of the enamine. Ketones (229) thus formed in an acidic medium afford fused 1,3-oxazines (230) (82JOC3339). Treatment of amines with silyl isothiocyanate gives not only pyrimidine derivatives but also l,3-oxazine-4-thiones (231) (81CCC2696). 

Trifluoroacetyl derivatives of amines were resolved on acids. 

Trifluoroacetyl derivatives of amines were resolved on trifluoro-acetylated-L-valyl-L-valine isopropyl ester coated in capillary columns. Better efficiency was obtained when a ureide, which was formed by the condensation of phosgene with L-Valine isopropyl ester, was coated on glass capillaries of about 70 meters in length and 0.25 mm i.d. Purity of the reagent (column coating) will affect resolution but not the relative peak areas. 

This form of activated DMSO is stable below —30°C, but suffer a Pummerer rearrangement above this temperature, resulting in the formation of methylthio-methyl trifluoroacetate (23). In fact, compound 23 reacts with alcohols in the presence of an amine, resulting in a very quick trifluoroacetylation. However, this trifluoroacetylation pathway is not operative in a properly perfonned Omura-Sharma-Swem oxidation, because alcohols are previously transfonned in afkoxy-dimethylsulfonium salts 24. 

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