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-bis(ferrocenylmethylene)-1-methylcycloheptanol gave the corresponding diferrocenyltrienes with a fixed s-cissoidal conformation of the double bond system, viz. 1,3-bis(ferrocenylmethylene)-2-methylene-cyclohexane and -cycloheptane, respectively. These trienes easily afford the products of linear and cyclodimerization 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.