- Temperature-dependent penetration of argon molecules into ultramicroporous tunnel of a fluoroorganic molecular crystal with alteration of its unit cell size
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A molecular crystal of octamethylene (S,S)-bis(2-hydroxy-3,3,3- trifluoropropanoate) with an ultramicroporous tunnel (Φ = 2.5-2.8 A) starts to adsorb argon (Φ = 3.6 A) at 150-140 K with 7% increase of the one direction of the orthorhombic unit cell. The alteration of the unit cell size indicates the penetration of argon into the tunnel and the soft nature of the microporous molecular crystal. Copyright
- Katagiri, Toshimasa,Takahashi, Satoshi,Kawabata, Koji,Hattori, Yoshiyuki,Kaneko, Katsumi,Uneyama, Kenji
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- Simple Access to (R)- and (S)-3,3,3-Trifluorolactic Acid and to (R)- and (S)-(Trifluoromethyl)oxirane
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Ethyl trifluoropyruvate (from hexafluoropropylene oxide) is reduced by NaBH4 to rac-trifluorolactic acid which is resolved on a 100-g scale by salt formation with (R,R)- and (S,S)-2-amino-1-phenyl-1,3-propanediol (readily available intermediates of industrial chloroamphenicol synthesis).The enantiomerically pure trifluorolactic acids (>99percent ee by GC analysis on cyclodextrin columns) are converted into (R)- and (S)-(trifluoromethyl)oxirane in an overall yield of 73percent by the following steps: esterification, THP protection of the OH group, LAH reduction and mesylation to the 2-THP-protected mesylate of 3,3,3-trifluoro-1,2-propanediol, and one-pot deprotection (Dowex 50) and cyclization (NaOCH2CH2OH) in ethylene glycol.The enantiomeric purity of the oxirane (b.p. 39 deg C, isolated on a 10-g scale) was determined by GC to be >99percent.Possible synthetic targets are mentioned which should be accessible in enantiomerically pure form from the (trifluoromethyl)oxirane described here. Key Words: Resolution by crystallization of diastereomeric salts / Perfluoropropylene oxide / Trifluoropyruvate / Capillary GC determination of ratios of enantiomers / Cyclodextrine-derived GC columns / Determination of the sense of chirality by chemical correlation / pKs of 3,3,3-trifluoro-2-hydroxypropanoic and 4,4,4-trifluoro-3-hydroxybutanoic acid
- Bussche-Huennefeld, Christoph von .,Cescato, Claudio,Seebach, Dieter
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p. 2795 - 2802
(2007/10/02)
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