Haloferrocenes: Syntheses and Selected Reactions

Abstract

Although haloferrocenes constitute important starting materials for many ferrocene-derived products with importance in a variety of fields such as materials science, medicinal chemistry and catalysis, only relatively few haloferrocenes out of the large number of possible examples have been prepared so far. The first part of this review summarizes the syntheses of all the homo- and heterohaloferrocenes known up to date. The second part summarizes typical reactions of haloferrocenes, namely lithiation followed by trapping with an electrophile, copper-mediated halogen substitution, coupling with formation of diferrocenyl derivatives, ortho-lithiation followed by trapping with an electrophile, palladium-catalyzed coupling reactions and finally miscellaneous reactions.1 Introduction2 Homohaloferrocenes2.1 Fluoroferrocenes2.2 Chloroferrocenes2.3 Bromoferrocenes2.4 Iodoferrocenes3 Heterohaloferrocenes4 Selected Reactions of Haloferrocenes4.1 Lithiation Followed by Trapping with an Electrophile4.2 Copper-Mediated Halogen Substitution4.3 Coupling with Formation of Diferrocenyl Derivatives4.4 ortho-Lithiation of Haloferrocenes4.5 Palladium-Catalyzed Reactions of Haloferrocenes4.6 Miscellaneous Reactions of Haloferrocenes5 Conclusions

Asymmetric synthesis of hetero-1,2,3,4,5-pentasubstituted ferrocenes

“…Thus, there are currently very few 1,2,3,4,5pentasubstituted ferrocenes bearing functional groups other than hydrocarbyls. Achiral 1,2,3,4,5-pentahalogenoferrocenes (Cl, Br, F) are accessible in a few steps, [15][16][17][18][19][20] while iterative metalation-functional group manipulation allows the tedious syntheses of pentasubstituted ferrocenes bearing up to three different substituents (Scheme 1). [21][22][23] Here, we report how the wise choice of substituents can enable hetero-1,2,3,4,5-pentasubstituted ferrocenes to be delivered, either as racemates or enantioenriched products, marking a milestone in metallocene science (Scheme 1).…”

Synthesis and Structures of 1,1′,2-Tribromoferrocene, 1,1′,2,2′-Tetrabromoferrocene, 1,1′,2,2′-Tetrabromoruthenocene: Expanding the Range of Precursors for the Metallocene Chemist’s Toolkit

“…[26] A recent review comprehensively covers those haloferrocenes including bromoferrocenes which have appeared in the literature to date. [27] We now turn our attention to the preparation of tetra-haloferrocene precursors and their derivatives, a subgroup of which are the 1,2,1´,2´-tetra-substituted compounds which have been less studied. We have already published a methodology which allows the preparation of some tetra-substituted phosphinoferrocenes [28] and we had briefly touched upon the search for tri-and tetrabromoferrocenes, however the yields obtained were rather low and scant attention was paid on their full characterisation.…”

Evidence for “Halogen‐Dance” and Ring‐Exchange Reactions in Chloro‐methylthio‐ferrocenes

“…[ 7 ] Many reactions and derivatives of this compound have been published, and the chemistry of an important subgroup of these derivatives, the haloferrocenes, has been reviewed recently. [ 8 ] Quite astonishing there are only very few reports on halogen dance reactions of haloferrocenes, [ 9 ] but the high synthetic potential of this reaction could be shown very recently by the successful asymmetric synthesis of the first hetero‐1,2,3,4,5‐pentasubstituted ferrocenes. [ 10 ] In all studies it was stated that generally in chloroaromatics the chloro substituent would not undergo the halogen dance reactions.…”