Elsevier

Tetrahedron

Volume 49, Issue 8, 1993, Pages 1541-1546
Tetrahedron

α-Amino-α-trifluoromethyl-phenylacetonitrile: A potential reagent for 19F NMR determination of enantiomeric purity of acids

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Abstract

α-Amino-α-trifluoromethyl-phenylacetonitrile, PhC(CF3)(CN)NH2, 2, in which the amino group is located on a crowded, chiral, quaternary carbon center, has been studied as a potential reagent for the 19F NMR determination of enantiomeric purity of chiral acids by conversion to their corresponding diastereomeric amides. The differences in the 19F NMR chemical shifts (Δδ) of the R,R/S,S versus R,S/S,R diastereomeric amides (8a–j) prepared from amine 2 and ten chiral acids range up to 0.266 ppm. Eight of the ten examples have Δδ in excess of the useful minimum of 0.02 ppm. These values are not notably superior to those of other known reagents.

α-Amino-α-trifluoromethyl-phenylacetonitrile, 1, has been converted to the mixture of diastereomeric amides (2). The 19F Chemical shift differences (Δδ = δRR − δRS) for a series of these diastereomers have been studied for the determination of enantiomeric purity of chiral acids (R1COOH). R1- = PhCH(OMe)-, PhCH(OCOMe)-, Ph CH(C2H5-, PhCH(t-Bu)-, Ph(OMe)(CF3)-, C2H5CH(CH3)- etc.

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1

On leave from the Institute of Chemistry, Slovak Academy of Sciences, Bratislava, Czechoslovakia.