Redox-mediated reactions of vinylferrocene: toward redox auxiliaries

Selective synthesis of (3-ferrocenylprop-2-en-1-yl)triphenylphosphonium iodide: crystal structure determination of two polymorphs

This work is part of a project studying the reactivity of a new ferrocenyl allylammonium salt, [3-(trimethylazaniumyl)prop-1-en-1-yl]ferrocene iodide, (1+)·I−, with different nucleophiles. With nitrogen-based nucleophiles, different ferrocenyl allylamine isomers have been synthesized successfully in good yield. Optimization of the basicity of the reaction medium has allowed selection of the best operating conditions to obtain the targeted isomer. In a similar way and in order to introduce phosphorus-containing functional groups, the reaction of ammonium salt (1+)·I− with a phosphorus nucleophile, namely triphenylphosphane, was attempted. It was then possible to isolate single crystals of (3-ferrocenylprop-2-en-1-yl)triphenylphosphonium iodide, [Fe(C5H5)(C26H23P)]I, which is shown to crystallize in two concomitant polymorphic forms, viz. a triclinic form, (I), in the space group P\overline{1}, and a monoclinic form, (II), in the space group P21/c. In the inter-ion packing of polymorph (I), the cations form bilayer ribbons via C—H...π and π–π stacking interactions. In polymorph (II), where π–π interactions do not occur, adjacent molecules are joined by C—H...π interactions into a one-dimensional helical arrangement along the b axis.

Radical Cation Cycloadditions Using Cleavable Redox Auxiliaries

The incorporation of an easily oxidized arylsulfide moiety facilitates the photocatalytic generation of alkene radical cations that undergo a variety of cycloaddition reactions with electron-rich reaction partners. The sulfide moiety can subsequently be reductively cleaved in a traceless fashion, affording products that are not otherwise directly accessible using photoredox catalysis. This approach constitutes a novel oxidative "redox auxiliary" strategy that offers a practical means to circumvent a fundamental thermodynamic limitation facing photoredox reactions.