Organocatalysis through Halogen-Bond Activation

Abstract

Haloperfluoroalkanes have been used as catalysts for the reduction of 2-phenylquinoline to its corresponding 1,2,3,4-tetrahydro derivative using a Hantzsch ester as reductand. The results suggest a substrate activation by halogen bonding.

Key words

amine synthesis - halogen bonding - imine reduction - organocatalysis - quinoline reduction

References and Notes

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11

General Procedure for the Hantzsch Ester Reduction of 1
A high-vacuum-dried Schlenk flask was charged with quinoline 1 (1.0 mmol), Hantzsch ester 2 (2.2 mmol), the perfluorohalogenated compound (0.1 mmol), and anhyd CH₂Cl₂ (14 mL). The mixture was stirred under inert atmosphere at the appropriate temperature for the indicated period of time. The solvent was removed under reduced pressure and the remaining product was purified by flash column chromatography on silica gel (3% EtOAc-pentane) to afford the corresponding 1,2,3,4-tetrahydroquinoline 3.