Functional ferrocene aldehyde

Attempts to make C2-symmetric ferrocenes by double lithiation of a bis-acetal met with only limited success . A second lithiation of the ferrocenylacetal 298 leads to functionalization of the lower ring of the ferrocene, in contrast with the second adjacent lithiation of the oxazolines described below. This can be used to advantage if, for example, the first-formed aldehyde 301 is protected in situ by addition of the lithiopiperazine 53 °, directing f-BuLi to the lower ring (Scheme 139) °. The same strategy can be used to introduce further functionalization to products related to 302. For example, silane 303, produced in enantiomerically pure form by the method of Scheme 138, may be converted to the ferrocenophane 304 by lithiopiperazine protection, lithiation and functionalization (Scheme 140) . 

Enantio-enriched enol esters - potential precursors of enantiopure a-arylalkanoic acids - have been prepared by asymmetric coupling of ketenes with aldehydes, using a chiral ferrocene bearing a dimethylaminopyridine function.20... 

Many reports have focused on the functionalization and derivatization of cyclo-pentadienyl groups bound to iron in ferrocene complexes. As an example, a series of ferrocenyl esters have been prepared via solvent-free reactions of ferrocenoyl fluoride with substituted phenols after microwave heating for just 1 min. " In the case of 4-bromophenol, the YIF was 1.2, but most substrates gave somewhat lower yields than the conventional method. However, the microwave approach did not require the addition of A, A -dimethylaminopyridine that was necessary conventionally. Other reports include a green approach to the acylation of ferrocene using the polymeric sulfonic acid Nation as an acid catalyst " and a one-pot approach to the synthesis of l,5-dioxo-3-substituted[5]ferrocenophanes from l,T-diacetylferrocene and aldehydes via a Claisen-Schmidt reaction. " " ... 

The first general method for mthenium(II)-catalysed oxidative dehydrogenative alkenylation of functional arenes showed successively the ability of carboxylate, heterocycle, ketone, aldehyde, amides, esters, and carbamates to behave as directing groups for C-H bond alkenylation and could also be applied to alkenes, ferrocenes, heterocycles, and protected phenols. 

Since 2011, the ruthenium(ll) catalysed alkenylation of arenes, alkenes, heterocycles, ferrocenes has been established as a catalytic method to produce a large variety of functional alkenes. The reaction requires a Ru(ll) catalyst associated with an oxidant such as Cu(0Ac)2.H20. More importantly using usually [RuCl2(arene)]2 catalyst with a slight excess of silver salt in the presence of an oxidant Cu(OAc)2 under air the alkenylation of (hetero)arenes and alkenes can be directed by weakly coordinating groups such as ketone, aldehydes, amides, carbamates, and esters. 

Xiao, Z.-P.,Cai, Z.-H., Liang, H., Jiang Lu, J. [2010]. Amphiphilic block copolymers with aldehyde and ferrocene-functionalized hydrophobic block and their redox-responsive micelles, ]. Mater. Chem., 20, 8375-8381. 

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