A simple synthesis of metallocene aldehydes from lithiometallocenes and N,N-dimethylformamide: ferrocene and ruthenocene aldehydes and 1,1'-dialdehydes

Article abstract of DOI:10.1016/0022-328X(93)83414-Q

Lithioferrocene, 1,1'-dilithioferrocene, lithioruthenocene and 1,1'-dilithioruthenocene all react with N,N-dimethylformamide in diethyl ether to produce the respective aldehydes.The lithiation of the two metallocenes can be steered to maximize the formation of only one of the two aldehydes by choosing either n-butyllithium in the presence of tetramethylethylenediamine (TMEDA) or t-butyllithium (^tBuLi) as the metallating reagent: ferrocene mono-aldehydes or 1,1'-dialdehydes are formed with good yields (91percent and 85percent respectively, based on ferrocene), lower yields (50percent) of ruthenocene-1,1'-dialdehyde were obtained under the standard conditions, because the 1,3,1'-trialdehyde also formed in significant (19percent) amounts.Monolithiation by ⁿBuLi and the formation of the ruthenocene monoaldehyde (yield, 66percent) are favoured when TMEDA is used in only catalytic amounts; lithiation of ruthenocene by ^tBuLi selectively leads to monolithioruthenocene and the mono-aldehyde (yield, 91percent).The products are easily purified by column chromatography.The simplicity and the high yield of these reactions make them much more desirable than the previously known multistep procedures.