Radical Additions of Alkyl 2‐Haloalkanoates and 2‐Haloalkanenitriles to Alkenes Initiated by Electron Transfer from Copper in Solvent‐Free Systems

Publisher Website
Google Scholar
Abstract
Alkyl 2‐iodoalkanoates 2, and 2‐iodoalkanenitriles 15 were added, with copper powder, to the 1‐alkenes 1a, e, f, and h, and to the alkenes 1b, c, d, and g with a 1,2‐dialkyl substituted double bond, to give, respectively, γ‐lactones and 4‐iodoalkanenitriles in very good yields. No solvent was used. The reaction is a free radical addition initiated by electron transfer from copper to the activated iodoalkane. Yields were lower using the respective bromo compounds. In situ formation of the iodo compounds, by addition of stoichiometric amounts of sodium iodide to the reaction mixture, gave improved yields. In the case of the methyl bromomalonates 6, the addition of sodium iodide proved to be unnecessary. The diastereoselectivity of the addition reaction by relative 1,3‐asymmetric induction was rationalized by consideration of the steric interactions of the substituents in the transition state which is formed in the process of iodine transfer to the chiral adduct radical.