Generation of oxyallyl cations by reduction of α,α′-diiodoketones under sonochemical or thermal conditions:: Improved methodology for the [4C(4π)+3C(2π)] cycloaddition reactions

An improved methodology to carry out [4C(4pi)+3C(2pi)] cycloaddition reactions of dienes and oxyallyl cations, is presented. The reaction starts from commercially available dienes and easy-handling alpha,alpha-diio-doketones, which are reduced by Zn (powder) or Zn/Cu couple to generate an oxyallyl cation as an intermediate. The reaction is carried out under mild thermal or sonochemical conditions at low tempera tures (from 0 to -44degreesC) and for short reaction times (< 15 min).