Samarium diiodide-promoted sequential coupling-aldol-reduction reactions of ferrocene-substituted enones

On treatment with SmI₂ in THF, 1-ferrocenyl-3-phenyl-2-propen-1-one and its related ferrocene-substituted enones underwent cyclodimerizations to give aldols (2a–g) with 3,4-trans configuration. Further reduction by using increased amounts of SmI₂ produced the corresponding diols. The stereoselectivity in this study was comparable with that in the SmI₂-promoted cyclodimerization of chalcones, but in contrast to that in the SmI₂-promoted cyclization-aldol reaction of 1,1’-dicinnamoylferrocenes. The thienyl- and furyl-substituted enones 5a and 5b could be visualized as an extended system of conjugated ketones, so that the SmI₂-mediated coupling reactions occurred preferably by linkages of β-carbons with thiophene or furan rings, giving compounds 8a,b and 9a,b.