3,3-Diethyl- and 3,3-dibenzyl-1,2-diferrocenylcyclopropenes

Organic & Biomolecular Chemistry Pub Date: 2003-11-12 DOI: 10.1039/B307408K

Abstract

Reactions of 2,3-diferrocenylcyclopropenone 1 with ethyl- and benzylmagnesium chlorides afford 3,3-diethyl- and 3,3-dibenzyl-1,2-diferrocenylcyclopropenes 2 and 3, respectively, and products of nucleophilic opening of the three-membered ring resulting from the addition of RMgCl to the carbonyl group, viz., saturated ketones (4,5-diferrocenylheptan-3-ones 4a,b and 3,4-diferrocenyl-1,5-diphenylpentan-2-ones 5a,b as ca. 3 ∶ 1 mixtures of two diastereomers) and other products. The spatial structures of compounds 2 and 4a were established by X-ray diffraction analysis of single crystals. Protonation of the cyclopropenes 2 and 3 with tetrafluoroboric acid at ?40 °C yields the corresponding 3,3-dialkyl-1,2-diferrocenylcyclopropylium tetrafluoroborates. Transformation of the latter into diferrocenylallylic cations upon increasing the temperature to 20 °C and their deprotonation under the action of N,N-dimethylaniline were studied. Electrochemical investigation of 1 and 2 shows that in both complexes the cyclopropene spacer allows electronic communication between the two outer ferrocenyl groups, this being notably greater for 2 than for 1.

Graphical abstract: 3,3-Diethyl- and 3,3-dibenzyl-1,2-diferrocenylcyclopropenes
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