D. Berger et al., Steroid imines as chiral ligands. Diastereoselective formation of (1-azadiene)Fe(CO)(3) complexes by sterically tuning the ligand coordination spheres, TETRAHEDR-A, 10(15), 1999, pp. 2983-2995
The condensation of steroid amines with alpha,beta-unsaturated aldehydes le
ads to the formation of chiral 1-azadiene ligands with a steroid core attac
hed to nitrogen. If the azadiene chain is situated at the D-ring of the ste
roid at C-16 or C-17, respectively, the two diastereotopic faces of the lig
and may be discriminated by different neighbouring substituents and their c
onfiguration. The reaction of these ligands with Fe-2(CO)(9) produces mixtu
res of diastereomeric (1-azadiene)Fe(CO)(3) complexes. By increasing the st
eric demands of the neighbouring groups it is possible to improve the diast
ereoselectivity of this complexation reaction from 1:1 mixtures using the l
east sterically hindered ligands to complete diastereoselectivity using the
azadiene derived from cinnamaldehyde and 16 beta-amino-3-methoxy-estra-1,3
,5(10)-triene-17 beta-ol. In addition, the molecular structure of [17 beta-
(3-phenyl-prop-2-enyliden)-amino-3-methoxy-estra-1,3,5(10)-triene]Fe(CO)(3)
was determined by X-ray structure analysis. (C) 1999 Elsevier Science Ltd.
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