Organoiron complexes in organic synthesis. Part 4. Direct ring connection between highly substituted centres. A potential approach to trichothecane synthesis

Abstract

Direct connection of six- and five-membered rings at their most highly substituted positions has been achieved by reaction of tricarbonyl(4-methoxy-1-methylcyclohexadienylium)iron hexafluorophosphate (4) with the potassium enolate of methyl 2-oxocyclopentanecarboxylate. The potential of this reaction in constructing the carbocyclic framework present in trichothecanes is demonstrated. The complex (5) crystallised in the monoclinic space group P2₁/c with a= 11.830(2), b= 6.823(4), c= 22.734(4)Å, β= 102.19(3)°, and Z= 4. The structure was solved by a combination of Patterson and Fourier techniques and refined to R 0.065 for 2 145 unique observed intensities.