Synthesis and some chemical properties of s-cis-diferrocenyltrienes. The role of stereoelectronic factors in cationic dimerization reactions

Dehydration of 2,6-bis(ferrocenylmethylene)-1-methylcyclohexanol and 2,7-bi s(ferrocenylmethylene)-1-methylcycloheptanol gave the corresponding diferro cenyltrienes with a fixed s-cissoidal conformation of the double bond syste m, viz. 1,3-bis(ferrocenylmethylene)-2-methylene-cyclohexane and -cyclohept ane, respectively. These trienes easily afford the products of linear and c yclodimerization by a cationic cyclodimerization mechanism as well as [4 2]-cyclodimers. They also form Diels-Alder adducts with azodicarboxylic and maleic acid N-phenylimides. The latter products undergo stepwise oxidative dehydrogenation on SiO2 up to the formation of phthalimide derivatives. (C ) 1999 Elsevier Science S.A. All rights reserved.