Mechanochemically Activated Asymmetric Organocatalytic Domino Mannich Reaction-Fluorination

Mechanochemical activation effectively mediated asymmetric organocatalytic domino Mannich addition followed by diastereoselective fluorination. The Mannich reactions of pyrazolones and to a lesser extent those of isoxazolones were effective under solvent-free ball-milling conditions. This reaction in combination with a chiral squaramide catalyst provided corresponding products in high yields and enantiomeric purities up to 99:1 e.r. and as a single diastereomer. DFT calculations revealed reasons for high diastereoselectivity.