Synthesis and characterization of novel polystyrene-supported TBD catalysts and their use in the Michael addition for the synthesis of Warfarin and its analogues

In the search for efficient and polymeric supports for organic bases to be used in environmentally friendly media and conditions, novel polystyrene-bound 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) has been prepared and characterized. Their catalytic properties have been tested in the Michael additions of 4-hydroxycoumarin to α,β-unsaturated ketones as a representative useful process for the syntheses of 4-hydroxy-3-(3-oxo-1-phenylbutyl)-2H-chromen-2-one (Warfarin™), 4-hydroxy-3-(1-(4-nitrophenyl)-3-oxobutyl)-2H-chromen-2-one (Acenocumarol™), 4-hydroxy-3-(1-(4-chlorophenyl)-3-oxobutyl)-2H-chromen-2-one (Coumachlor™), and 4-hydroxy-3-(1-(4-methoxyphenyl)-3-oxobutyl)-2H-chromen-2-one. Products were obtained in high to quantitative conversion yields. The novel catalytic systems showed promising catalytic properties, and they could be all easily recovered by filtration and have been reused for three representative consecutive runs without any significant lowering of their activity.