Remote diastereoselective control via organoiron methodology: Stereoselective preparation of 4,6-, 5,7- and 6,8-dien-2-ol (tricarbonyl)iron complexes

The diastereoselective preparation of 2,3-, 2,4- and 2,5-diol iron complexes was accomplished in the following fashion: (2,4,6-octatriene)Fe(CO)(3) undergoes diastereoselective osmylation to provide (4,6-octadien-2,3-diol)Fe(CO)(3); (4-hydroxy-5,7-nonadien-2-one)Fe(CO)(3) may be reduced in a diastereoselective fashion to give mixtures predominating in either the syn- or anti-(5,7-nonadien-2,4-diol)Fe(CO)(3); and diastereospecific addition of MeTi((OPr)-Pr-i)(3) to the lactol of (5-hydroxy-6,8-decadienal)Fe(CO)(3) gives (6,8-decadien-2,5-diol)Fe(CO)(3). In each of the cases noted above, the hydroxyl group adjacent to the (diene)Fe(CO)(3) group may be removed via ionic hydrogenation. The ionization of this hydroxyl is rationalized on the basis of the intermediacy of a transoid (pentadienyl)Fe(CO)(3) cation species.