Recyclable Palladium-Catalyzed Carbonylative Cyclization of Trifluoroacetimidoyl Chlorides with Nitro Compounds Towards 2-(Trifluoromethyl)quinazolin-4(3H)-ones

A new mesoporous SBA-15-anchored Schiff base and phosphine mixed bidentate palladium(II) complex [SBA-15-N, P-PdCl₂] was prepared via immobilization of 3- aminopropyltriethoxysilane on SBA-15, followed by condensation with 2–(diphenylphosphino)benzaldehyde and then coordination with PdCl₂. With the use of 5 mol% of SBA15-N, P-PdCl₂ as catalyst, the carbonylative cyclization between trifluoroacetimidoyl chlorides and nitro compounds proceeds smoothly in 1,4-dioxane at 120 °C with Na₂CO₃ (2 equiv.) as base by using Mo(CO)₆ (2 equiv.) as both a solid CO source and a reductant, yielding a variety of 2-(trifluoromethyl)quinazolin-4(3H)-ones in 68–94% yields. The SBA-15-N, P-PdCl₂ complex can be easily separated by a simple centrifugation process and recycled more than 8 cycles without a remarkable loss of activity. The current protocol not only solves the basic problem of expensive palladium catalyst recovery and reuse, but also prevents palladium contamination in the final product.

Graphical Abstract

A highly efficient heterogeneous palladium-catalyzed carbonylative cyclization of trifluoroacetimidoyl chlorides, nitro compounds and Mo(CO)6 towards 2-(trifluoro- methyl)quinazolin-4(3H)-ones is described.