Catalytic asymmetric [4 + 1] cycloaddition to synthesize chiral pyrazoline-spirooxindoles

Abstract

An asymmetric formal [4 + 1] cycloaddition of N-unprotected oxindole 3-pyridinium salts and α-halo hydrazones to access chiral pyrazoline-spirooxindoles is realized by using a chiral N,N’-dioxide-Pr(OTf)3 complex as catalyst. The...

Organocatalytic Diastereoselective (4 + 1) Cycloaddition of o-Hydroxyphenyl-Substituted Secondary Phosphine Oxides

“…However, despite these strategies, (4 + 1) cycloadditions of SPOs remain underdeveloped (Scheme d). In fact, (4 + 1) cycloaddition, especially organocatalytic (4 + 1) cycloaddition, is a powerful tool for the synthesis of five-membered heterocycles. , Thus, it is highly valuable to develop organocatalytic (4 + 1) cycloaddition of SPOs for the construction of phosphorus-containing benzo five-membered heterocyclic skeletons.…”