Steroid imines as chiral ligands.: Diastereoselective formation of (1-azadiene)Fe(CO)3 complexes by sterically tuning the ligand coordination spheres

The condensation of steroid amines with alpha,beta-unsaturated aldehydes leads to the formation of chiral 1-azadiene ligands with a steroid core attached to nitrogen. If the azadiene chain is situated at the D-ring of the steroid at C-16 or C-17, respectively, the two diastereotopic faces of the ligand may be discriminated by different neighbouring substituents and their configuration. The reaction of these ligands with Fe-2(CO)(9) produces mixtures of diastereomeric (1-azadiene)Fe(CO)(3) complexes. By increasing the steric demands of the neighbouring groups it is possible to improve the diastereoselectivity of this complexation reaction from 1:1 mixtures using the least 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. All rights reserved.