PREPARATION OF 1,6-DIMETHYL-1,5-CYCLOOCTADIENE

PURPOSE:To obtain the titled substance, by dimerizing isoprene in the presence of a catalyst consisting of an iron carboxylate or a beta-diketonic compound, an organoaluminum compound or organomagnesium compound and a 2,2'-dipyridyl derivative containing an electron donative substituent group. CONSTITUTION:Isoprene is catalytically cyclodimerized to give the titled substance. In the process, a catalyst consisting of (A) an iron carboxylate, e.g. iron (III) acetate, iron (II) lactate or iron (II) benzoate, or a beta-diketonic compound of formula I (n is 2 or 3; R' and R'' are alkyl, aryl or aralkyl), (B) a compound of formula II (R is alkyl, aryl, etc.; X is R , alkoxyl, H, etc.; l is 1-3) or formula III (R is alkyl, aryl, etc.; Y is halogen; m is 1 or 2) and (C) a compound having an electron donative substituent group of formula IV (R -R are alkyl, alkoxyl, amino, H, etc.) is used to give the titled substance in high selectivity.