2-(Diphenylphosphino)benzoyl-Substituted Calix[4]arene: Efficient Organocatalyst in Aza-Morita-Baylis-Hillman Reaction of N-Sulfonated Imines with Methyl Vinyl Ketone

A novel bifunctional organocatalyst 5,11,17,23-tetra­butyl-25-[2-(diphenylphosphino)benzoate]-26,27,28-trihydroxycalix-[4]arene (LB3) was synthesized and applied to promote the aza-Morita-Baylis-Hillman (aza-MBH) reaction of N-sulfonated im­ines with methyl vinyl ketone. It was found that in the presence of acidic additives the reaction rate could be accelerated to give aza-MBH adducts in good to excellent yields. Compared to our previous phosphine-containing calix[4]arene LB1, the novel catalyst was more effective.