Ultrasound catalysed formation

Nevertheless, the two methods developed for formation of ferrilactone complexes show wider substrate tolerance than either the thermal or photo-lytic reactions and avoid problems that can occur at higher temperature, such as decarbonylation, decarboxylation or metal-catalysed hydrogen shifts [265]. They both give comparable yields of ferrilactone under the conditions described (see Table 8). The one exception is the case of vinyl epoxide (59), when four equivalents of Fe2(CO)9 were required [206]. This is probably due to coordination of the reactive species to the oxygens of the cw-dibenzoyl system reducing the effective concentration of tetracarbonyliron in solution. Conversely, the ultrasound reaction presumably takes place at the surface of the solid Fe2(CO)9 where the local concentration of Fe(CO)4 is much higher and this is reflected in the yields obtained. 

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