Assessing the halogen effect in Diels-Alder reactions involving chiral α-halo enones. A combined experimental and DFT computational approach

An experimental and computational study was conducted to assess the effect of chlorine and bromine substitution in Diels-Alder reactions involving chiral alpha-halo enones as dienophiles. An important rate enhancement was observed in the case of acyclic dienes, while the use of cyclic dienes resulted in prolonged reaction times and lower yields. DFT calculations suggest that these reactions are governed by finely balanced geometric and electronic features at the TSs. (C) 2011 Elsevier Ltd. All rights reserved.