FC-72 Perfluorohexanes

Curran and coworkers reported on organic-fluorous-organic triphasic systems using a glass U-tube, which is useful for the separation of fluorous and non-fluo-rous compounds [17]. An example is shown in Fig. 3.5-2. A racemic ester with a fluorous ponytail was treated with a lipase to resolve the racemic ester into (S)-ester 

Using a glass U-tube as a reaction tool, Nakamura and coworkers expanded phase-vanishing methods to include reagents Hghter than fluorous solvents, such as thionyl chloride and phosphorus trichloride [19]. 

2 For historical views and definitions of fluorous chemistry, see Symposium-in-Print on fluorous chemistry, J. Gladysz, D.P. Curran, Tetrahedron 2002, 58, 3823. 

Paquette, Encyclopedia of Reagents for Organic Synthesis, Vol. 7, J. Wiley Sons, Chichester, 1995, p. 5131. 

Kokai Tokkyo Koho, 1991, 03276065 Jpn. Kokai Tokkyo Koho, 1981, 56053458 Jpn. Kokai Tokkyo Koho, 1981, 56012551. 

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The enantioselective synthesis of a-amino acids employing easily available and reusable chiral catalysts or reagents presents clear advantages for large-scale applications. Accordingly, recyclable fluorous chiral phase-transfer catalyst 31 has been developed by the authors group, and its high chiral efficiency and reusability demonstrated in the asymmetric alkylation of 2. After the reaction, 31 could be easily recovered by simple extraction with FC-72 (perfluorohexanes) as a fluorous solvent and used for the next run, without any loss of reactivity and selectivity (Scheme 5.17) [23]. 

As expected, these compounds are sparingly soluble in common organic solvents except acetone and ethyl acetate, but well soluble in fluorocarbon solvents such as FC-72 (perfluorohexanes), FC O (per-fluorododecanes), and octafluorocyclopentene. 

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