Iodocyclization: Past and Present Examples

Many reagents have been utilized to accomplish the cyclization of organic compounds to utilize the resulting product in the synthesis of natural products and bioactive compounds. The commercially available iodine has been frequently utilized in the cyclization of several compounds such as olefinic benzyl ethers, dimethylalkenyl malonates, allylic fluorides, propargylic esters, enamides, allylated β-hydroxyketones,4,5-alkadienols, CF3-allylmorpholinones, lithium 2-(vinyl)-dithiobenzoate derivatives, 2,4-dialkenyl-1,3-dicarbonyl compounds, allylic fluorides, 1-(methylthio)-3-tosylhexa-1,3-diene-5-ynes, etc. Some of these cyclic compounds have been utilized in the synthesis of sesquiterpenes: davanone, artemone, junenol, glutinosone; diterpene pisiferic acid, iodoalkyl, dihydrofurans, β-fluorinated-γ- lactones, substituted 2-iodoindolizinones, iodinated arenes etc. The present review concentrates mainly on the recent progress of cyclization mediated by iodine. Some past examples have also been included for a comparative study.