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New Synthesis and Chirality of (−)‐4,4,4,4′,4′,4′‐Hexafluorovaline
Author(s) -
Eberle Marcel K.,
Keese Reinhart,
StoeckliEvans Helen
Publication year - 1998
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19980810117
Subject(s) - chemistry , trifluoromethyl , diastereomer , chirality (physics) , yield (engineering) , hydrochloride , stereochemistry , acrylic acid , medicinal chemistry , organic chemistry , chiral symmetry , alkyl , physics , materials science , monomer , quantum mechanics , nambu–jona lasinio model , metallurgy , quark , polymer
(−)‐( R )‐4,4,4,4′,4′,4′‐Hexafluorovaline hydrochloride (( R )‐ 5 ) of 98% ee is prepared from β,β‐bis(trifluoromethyl)acrylic acid (= benzyl 4,4,4‐trifluoro‐3‐(trifluoromethyl)but‐2‐enoate; 1 ) in 4 steps with an overall yield of 9.6%. Key step is the separation of the TsOH salts of the diastereoisomers obtained by anti‐Michael addition of (+)‐( R )‐1‐phenylethylamine ( 2 ) to 1 (→ ( R,R )‐ 3 ). In contrast to the published ( S )‐chirality, the X‐ray structure analysis of ( R , S )‐ 6 reveals, that ( R )‐chirality has to be assigned to the levorotatory (−)‐4,4,4,4′,4′,4′‐hexafluorovaline hydrochloride.
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