ETHYNYLFERROCENES BY DIRECT INTRODUCTION OF ACETYLENES

Protected ethynylferrocenes were prepared by one-pot-reaction sequences, starting from 1,1'-dilithioferrocene.tmeda via intermediate cupration and subsequent coupling with iodoethynes. The dimethylsulphide complex of copper(I) iodide proved to be the most convenient in situ cupration coupling reagent for this inverse Stephens-Castro reaction type. The corresponding monosubstituted ethynylferrocenes could be also isolated by use of half equivalents of the cupration system, i.e. the iodoethynes, followed by quenching excess ferrocenyllithium functionalities. As primary examples, 1,1'-bis(trimethylsilylethynyl)ferrocene (I), 1-trimethylsilylethynylferrocene (II), 1,1'-bis(3-hydroxy-3-methylbut-1-ynyl)-ferrocene (III), and 1-(3-hydroxy-3-methylbut-1-ynyl)ferrocene (IV), half-deprotected 1-ethynyl-1'-(3-hydroxy-3-methylbut-1-ynyl)ferrocene (V) and 1-(3-hydroxy-3-methylbut-1-ynyl), 1'-iodoferrocene (VI) are presented. Full deprotection to 1,1'-diethynylferrocene confirmed the reported instability of the latter compound owing to spontaneous polymerisation even with exclusion of water and oxygen. All new compounds (I, III, IV, V, VI) were characterized by MS, IR, NMR and elemental analysis.