The <i>epi</i> -Matteson Reaction: Addition of Sodium Iodide in the Substitution Step Allows for a Stereodivergent Outcome

The product of a Matteson homologation sequence is determined by the chiral director. Upon iterative application, this limits stereochemical variability. In this work, a method for the stereodivergent synthesis of alkyl-substituted Matteson products is described. By exploiting a new stereoselective mechanism a diastereomeric mixture of α-iodo boronic esters is reacted in the presence of NaI. The preparative demand of the new protocol is comparable to classic Matteson homologations.