Bridged ferrocenes—I

The Oxidation of Organic Compounds by Active Manganese Dioxide

“…the reaction takes essentially a single course; for example, N-methylaniline (546) gave formanilide (547) in 85% yield. and a little azobenzene (548; 2.5% yield); N.N-dimethylaniline (549) was oxidized to N-methylformamide (550) in 80% yield. 49 all according to route (a).…”

Microwave-assisted synthesis of 1,5-dioxo-3-substituted [5]ferrocenophanes

“…According the mechanism previously proposed [26], the first product of Claisen-Schmidt condensation between 3 and 4 is the 1-acetyl-1 0 -(b-ferrocenylacryloyl)ferrocene 5b, which can further react to afford the 1,1 0 -diacryloylderivative 6b (path a) or undergo an intramolecular Michael addition leading to the formation of the interannular bridge of 2b (path b). Also compound 6b could contribute to the formation of the ferrocenophane system via an alkali-catalyzed retro-aldol reaction and subsequent intramolecular Michael addition [32] (Scheme 1).…”

“…Obtained from the reaction of 3 and benzaldehyde, compound 2a was known [26,32] but its NMR spectra were not reported. 1 …”

“…Many of them are derived from [5]ferrocenophane-1,5-dione, 1 (R = H) (see Fig. 1), obtained by a sequence of Friedel-Crafts acylation of acetylferrocene with 3-chloropropionyl chloride followed by base-catalyzed cyclization [26]. The related 3-substituted [5]ferrocenophane-1,5-diones 2 (R = Ar, alkyl) can be prepared by means the reaction of 1,1 0 -diacetylferrocene, 3 and aldehydes in NaOH ethanolic solution [27][28][29][30][31], resulting in a mixture of a,b-unsaturated ferrocenylketones and ferrocenophanes, whose selective formation was obtained in some cases [30,31].…”

“…The related 3-substituted [5]ferrocenophane-1,5-diones 2 (R = Ar, alkyl) can be prepared by means the reaction of 1,1 0 -diacetylferrocene, 3 and aldehydes in NaOH ethanolic solution [27][28][29][30][31], resulting in a mixture of a,b-unsaturated ferrocenylketones and ferrocenophanes, whose selective formation was obtained in some cases [30,31]. Improved methods for the synthesis of 2a (R = Ph) starting from 5a [26] or 6a [32] independently prepared by Friedel-Craft acylations and treated with NaOH ethanolic solution for long time (up to 65 h), have been proposed.…”