Cooperative\nDiarylborinic Acid/Chloride-Catalyzed\nFormal S<sub>N</sub>i Reaction of <i>cis</i>-4-Hydroxymethyl-1,2-Cyclopentene\nOxides

A catalytic formal S<sub>N</sub>i reaction was designed\nto achieve\nstereoretentive products for <i>cis</i>-4-hydroxymethyl-1,2-cyclopentene\noxides by using diarylborinic acid as a dual role catalyst and chloride\nas a catalytic transient nucleophile through a double-displacement\nmechanism. This reaction offers the advantages of a low catalyst loading\nof 0.1 mol % and wide substrate scope, even including <i>N</i>-substituents. The use of chiral boron acid as a catalyst for this\nreaction was also attempted.