Application of Biginelli reaction to the synthesis of ferrocenylpyrimidones and [3]-ferrocenophane-containing pyrimido[4,5-d]pyrimidinediones

A series of ferrocene-containing mono- and bis-dihydropyrimidines (DHP’s) were prepared by boric acid mediated three-component Biginelli reactions of formyl- and 1,1′-diformylferrocene, 1,3-dioxo-components and urea. A few further transformations including hydrogenolysis of a benzyl 4-ferrocenyl-DHP-5-carboxylate were also performed. Novel cis-fused saturated pyrimido[4,5-d]pyrimidine-2,7(1H,3H)-diones incorporating [3]-ferrocenophane moiety were constructed by means of iron(III)-catalyzed Biginelli-like condensations of 1,1′-diformylferrocene with urea and in situ generated methyl ketone-derived silyl enol ethers. The structures of the new compounds were established by IR and NMR spectroscopy, including HMQC, HMBC and DEPT measurements.