José Manuel Méndez Stivalet

The behavior of 3-ferrocenyl-1-methyl-1,2-pentamethyleneallyl and 1,5-diferrocenyl-3-methyl-2,4-tetramethylene-1,4-dienyl carbocations in the cationic dimerization of 1,3-dienes

Abstract 3-Ferrocenyl-1-methyl-1,2-pentamethyleneallyl carbocation 9 and 1,5-diferrocenyl-3-methyl-2,4-tetramethylene-1,4-dienyl carbocation 10 are transformed into linear 21 and cyclic 28 dimers, respectively, in low yields under conditions of the cationic dimerization (treatment with N,N -dimethylaniline). The former is preferentially deprotonated into 1-ferrocenylmethylidene-2-methylidenecycloheptane ( 19 ) and 3-ferrocenylmethylidene-2-methylcycloheptene ( 20 ), while the latter is reduced into 1,3-bisferrocenylmethylidene-2-methylcycloheptane ( 26 ). However, a linear dimer was obtained in the reaction of salt 9 with s - cis -diene 19 , while the reaction of salt 10 with 1,3-bisferrocenylmethylidene-2-methylidenecycloheptane ( 27 ) results in a cyclodimer 28 together with a linear dimer 29 . The results obtained corroborate the stepwise mechanism of cationic cycloaddition of 1,3-dienes and manifest the role of the electronic factor in the intramolecular cyclization of an intermediate linear dimeric allylic cation.

Thermolysis and [3+2]‐Cycloaddition Reactions of 2,3‐Diferrocenyl‐ and 2,3,‐Diruthenocenylcyclopropenones

Abstract 2,3‐Diferrocenyl‐ and 2,3‐diruthenocenylcyclopropenone undergo thermolysis at ∼180°C with opening of the small ring via ketenocarbenes. Intramolecular transformation of the latter occurs with elimination of CO to yield dimetallocenylacetylenes. Alternatively, they enter into 1,3‐dipolar cycloaddition reactions with C≡C or C˭C multiple bonds to give cyclopentadienone or cyclopentenone derivatives, respectively.

3,3-Diferrocenylcyclopropene

Abstract Dehydrohalogenation of isomeric 2-chloro- and 2-bromo-1,1-diferrocenylcyclopropanes (Z- and E-isomers with respect to the ‘bisecting’ ferrocenyl substituent) under the action of ButOK in DMSO afforded 3,3-diferrocenylcyclopropene. In solution, this underwent facile opening of the small ring to give 3-ferrocenyl-1H-cyclopentaferrocene (∼55%) and 1,1-diferrocenylpropene (15%). The spatial structure of Z-2-chloro-1,1-diferrocenylcyclopropane and 1,1-diferrocenylcyclopropane were elucidated by X-ray diffraction analysis of a single crystal.