I. Electrophilic Substitution Reactions of Some Substituted Ferrocenes. II. The Effects of Heteroannular Substituents on the Rates of Solvolyses of Methylferrocenylcarbinyl Acetates; a Comparison with Substituent Effects in Other Reactions of Ferrocene

Citation

Hall, David Warren (1963) I. Electrophilic Substitution Reactions of Some Substituted Ferrocenes. II. The Effects of Heteroannular Substituents on the Rates of Solvolyses of Methylferrocenylcarbinyl Acetates; a Comparison with Substituent Effects in Other Reactions of Ferrocene. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/D0MY-K780. https://resolver.caltech.edu/CaltechTHESIS:04182012-093046041

Abstract

Part I. The directive effects of substituents in ferrocene have been investigated by means of Friedel-Crafts acetylation studies. It was demonstrated that the effect of an alkoxycarbonylamino group is comparable to that of an alkyl group in the acetylation of 1,1'-disubstituted ferrocenes. Contrary to expectations, acetylation of acetamide- and alkoxycarbonylaminoferrocenes gave chiefly the heteroannular isomers. Only small amounts of the 1, 2-isomers were formed; no 1,3-isomers were isolated.

The iodine in iodoferrocene was replaced by hydrogen under the conditions of the Friedel-Crafts reaction. Bromo- and chloroferrocenes were readily acetylated; only heteroannularly substituted isomers were formed.

Part II. The nature of the transmission of substituent effects from one cyclopentadienyl ring of ferrocene to a reaction center on the other ring was investigated by means of solvolyses studies on heteroannularly substituted methylferrocenylcarbinyl acetates. The evidence indicates that inductive or field effects predominate, and that resonance interactions play at most a minor role.

Substituents possessing unshared pairs of electrons can apparently undergo nucleophilic participation with the central iron atom. This interaction very likely requires that the ring bearing the substituent be shifted or tilted in the transition state so that the substituent can be sufficiently close to the iron atom.

A linear relationship has been shown to exist between substituent effects in all side-chain reactions of ferrocene reported to date and the reversible quarter-wave oxidation potentials of the appropriately substituted ferrocenes.

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