Iodine(III)-Mediated Ring Contraction of 1,2-Dihydronaphthalenes: Mechanistic Insight by Computational Investigations

The metal-free synthesis of the trans-1,3-disubstituted indanes through the ring contraction of 1,2-dihydronaphtalenes, promoted by PhI(OH)Ts (HTIB or Koser's reagent), was computationally studied using Density Functional Theory (DFT) methods. DFT calculations suggest that the stereoselectivity of these reactions arises through the torsional effects during the electrophilic addition of the hypervalent iodine to the double bond of the 1,2-dihydronaphthalene. Furthermore, the fundamental role played by the solvent (MeOH) during the nucleophilic addition step was analyzed by DFT methods on a mixed continuum-microsolvation model system.