conditions, malondialdehyde 2 and n-pentylmalondialdehyde 3 yield bicyclo[3.3.l]nonane derivatives 4 (67%) and 5 (21%), respectively. This new reaction is reminiscent of the formation of tropinone derivatives from 3-oxoglutarate, succindialdehyde, and methylamine['dl.The yields of 4 and 5 fall off as the pH is raised above 8or lowered below 7. The yield of phenol 6 obtained from 1 and 2 is maximal (43%) at pH 4.5. In contrast, the yield of phenol 7 is maximal (26%) at p H 7, which explains why the yield of 5 is lower than that of 4. Remarkably, under Prelog's conditions only 4 is produced from 1 and 2, although the yield (49%)[" is lower than under physiological conditions. Only 10Y0 of 7 and no 5 is observed with 1 and 3 under these conditions. Thus, compounds 4, 5 , and 7 are all best prepared under physiological conditions.The preferred formation of 6 at low p H has been adduced as supporting evidence for the intermediacy of dimethyl 2-oxo-5-hydroxy-3-cyclopentene-1,3-dicarboxylate in the Weiss reaction of 1 with glyoxal at pH 5I3"l. Given the precedents""] for phenol formation and the driving 151 a) S. H. Bertz, G. Dabbagh, P. Cotte, J. Org. Chem. in press: b) S. H. Bertz, J.Iron-molybdenum-sulfur clusters"] are of interest, inter alia, because of their occurrence in nitrogenase[*I. We have now prepared a new cluster of this type, namely 3, with the unprecedented framework stoichiometry (Fe2M02S2), by reaction of the diiron complex lI3] with the dinuclear molybdenum compound 2 (Cp =qs-C5H5) in toluene.
IFe2Mo2(tl5-C5H5)2(~3-S)t(~3-C0)2(CO)~1* *Reaction (a) is the third example141 for the formation of a heterotetranuclear cluster from 1 and a dinuclear species. The high reactivity of the MoMo triple bond in 2 towards electrophiles and nucleophiles151 facilitates reaction under very mild conditions.
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