Carbohydrate functionalization using cationic iron carbonyl complexes

Selective Iron-Mediated C- and O-Addition of Phenolic Nucleophiles to a Cyclohexadiene Scaffold Using Renewable Precursors

“…Attempted demetalation of the C -addition product 3a using basic hydrogen peroxide or ceric ammonium nitrate resulted in decomposition of the starting material, possibly caused by oxidation of the phenol group. Using the milder oxidant trimethylamine N -oxide yielded the aromatized demetalated product, as indicated by earlier studies in the group, producing product 6 in excellent yield (Scheme , reaction a). To investigate if the uncomplexed diene could also be obtained from the same precursor, compound 3a was protected as a tert -butyldimethylsilyl ether 7 to make it less sensitive to oxidation (Scheme , reaction b).…”

“…Once formed, the complex can react with a wide range of nucleophiles, including alcohols, 19 amines, 26 amides, 27 azide, 16 hydride, 16 carbamate, 17 thiols, 28 enolates 26 and malonates, 29 allyl silanes, 30 electron rich aromatics 31 and heterocycles, 30 organocuprates, 26 organolithium reagents, 20 organozinc reagents, 32 Grignard reagents, 26 phosphines, 33 phosphites, 34 and halides. 35 At the outset of our investigation, we aimed to perform the selective C-and O-addition of phenolic nucleophiles to cationic η 5 iron carbonyl cyclohexadienyl complex 1 (Scheme 2).…”

“…We opted for the second of these strategies in the preparation of the initial cationic iron complex. Once formed, the complex can react with a wide range of nucleophiles, including alcohols, amines, amides, azide, hydride, carbamate, thiols, enolates and malonates, allyl silanes, electron rich aromatics and heterocycles, organocuprates, organolithium reagents, organozinc reagents, Grignard reagents, phosphines, phosphites, and halides …”

Azulene Functionalization by Iron-Mediated Addition to a Cyclohexadiene Scaffold

“…The free diene could also be liberated without concomitant aromatization. This has previously proved to be difficult for iron complexes possessing an aromatic substituent, which is not conjugated to the diene. , Photolytic demetallation of the methoxy-substituted adduct 14 instead resulted in the formation of unsaturated ketone 34 in a 74% yield (Scheme , entry 2). This type of reactivity is known upon decomplexation of 2-methoxy-substituted iron carbonyl cyclohexadiene complexes and provides access to a different compound class in terms of substituted azulenes.…”