Three enantiopure fluorous thioureas featuring a free -NH2 group were synthesized by direct addition of aromatic isothiocyanates bearing a single n-C8F17 substituent in the ortho, meta and para position, respectively, to enantiopure (1R,2R)-1,2-diaminocyclohexane. The catalytic behavior of these bifunctional molecules was assessed in representative Michael-type reactions. The three fluorous thioureas performed similarly in all the reactions tested, thus showing that the position of the fluorous ponytail does not have a major influence on the catalytic behavior of this class of compounds. In particular, excellent enantioselectivities (up to 99% ee) and yields (up to 98%) were obtained for the addition of aliphatic aldehydes to maleimides to give α-substituted succinimides. Recyclability of these primary amine-based thioureas was found to be limited by the concurrent formation of imine-derivatives during the catalytic process, leading to a structural modification of the organic catalyst.

Synthesis and catalytic activity of fluorous chiral primary amine-thioureas / S. Orlandi, G. Pozzi, M. Ghisetti, M. Benaglia. - In: NEW JOURNAL OF CHEMISTRY. - ISSN 1144-0546. - 37:12(2013), pp. 4140-4147.

Synthesis and catalytic activity of fluorous chiral primary amine-thioureas

M. Benaglia
2013

Abstract

Three enantiopure fluorous thioureas featuring a free -NH2 group were synthesized by direct addition of aromatic isothiocyanates bearing a single n-C8F17 substituent in the ortho, meta and para position, respectively, to enantiopure (1R,2R)-1,2-diaminocyclohexane. The catalytic behavior of these bifunctional molecules was assessed in representative Michael-type reactions. The three fluorous thioureas performed similarly in all the reactions tested, thus showing that the position of the fluorous ponytail does not have a major influence on the catalytic behavior of this class of compounds. In particular, excellent enantioselectivities (up to 99% ee) and yields (up to 98%) were obtained for the addition of aliphatic aldehydes to maleimides to give α-substituted succinimides. Recyclability of these primary amine-based thioureas was found to be limited by the concurrent formation of imine-derivatives during the catalytic process, leading to a structural modification of the organic catalyst.
Settore CHIM/06 - Chimica Organica
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/228825
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