Iron-catalyzed decarbonylation

In 2012 Ryu and his colleagues reported the iron-catalyzed decarbonylation of aliphatic carboxylic acids to a-olefins (Scheme 11.7) [32]. In their mechanism study, they found the formation of CO but not CO2. If the reaction was carried out under low or no pressure (0-5 bar) of carbon monoxide, internal an olefin was observed [33]. In the proposed reaction mechanism, the reaction starts from acid anhydride, which was produced from the reaction of substrate and AC2O. Then it reacts with the in situ-formed iron-carbonyl complex, which was generated by FeCl2, phosphine ligand, KI, and CO, and decarbonylation occurred under high temperatures. Notably, Fe2(CO)9, Fe3(CO)i2, [Fe(CO)2Cp]2 did not give the decarbonylation product. 

Scheme 11.7 Iron-catalyzed decarbonylation of carboxylic acid...

The conversion of 1,3-diketones to 1,2-diketones via the formal C-C=0 bond cleavage was developed using an iron catalyst (Scheme 6.10) [28]. The reaction is initiated by oxidation of the methylene carbon to a carbonyl by tert-butyl nitrite (53 56), followed by iron-catalyzed decarbonylation (56 54). 

For a few combinations of less reactive dienes and dienophiles, transition metal catalyzed variants of the Diels Alder reaction have been developed. An example is the cycloaddition of an unpolar diene and an unactivated alkyne however, except when the reaction is catalyzed with iron, nickel, cobalt, or rho-dium(I) complexes, the temperature required often causes competing decomposition, even for the intramolecular version. [2] Wilkinson s catalyst [3] - tris(triphenylphosphane)rho-dium(I) chloride - frequently used for hydrogenations and for decarbonylations, permits the cyclization of 4 to the annelated cyclo-hexadiene 5 in excellent yield in only 15 minutes at 55 °C in trifluoroethanol as solvent (Scheme 2). [2c]... 

ACS are present in methanogens, acetogens and carboxydotrophic microorganisms where they catalyze the synthesis and/or the decarbonylation of acetylCoA according to the following reaction, where CoFeS correspond to a correnoid/cobalt containing iron-sulfur protein [158, 165]. 

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