IODOCARBOCYCLIZATION REACTION

''Halocarbocyclization reaction'', which involves intramolecular attac k of a carbon nucleophile on a double bond activated by an electrophil ic halogenating reagent, has so far been uncommon, We report here that ''iodocarbocyclization reaction'' of alkenyl or alkynylmalonate deriv atives proceeded in good yields in the pre sence of Ti(OR)(4) and I-2 to give cyclized products in regio- and stereocontrolled manner, The d iastereoselective iodocarbocyclization with 4-pentenylmalonate derivat ives having a chiral center at the 2 or 3 position and allylmalonate h aving a chiral auxiliary in ester part have also been investigated. Fu thermore, the reaction of 4-pentenylmalonates using a catalytic amount of a chiral titanium alkoxide in the presence of I-2 and 2,6-dimethox y-pyridine proceeded with high enantioselectivity to give good yields of cyclopentane derivatives. The origin of enantioselectivity in this catalytic asymmetric reaction is also described.