Tricarbonylchromium complexed arenes are widely used in organic synthesis because the Cr(CO)3 unit, in addition to its electron withdrawing character, imparts a third dimention to the molecule, therefore the ortho and meta unsymmetrically disubstituted complexes are chiral and in many cases can be resolved into the corresponding enantiomers. Tricarbonyl (ortho- substituted benzaldehyde) chromium complexes are the most commonly used in this class of compounds. As the Cr(CO)3 unit occupies one face of the arene and the ortho substituent, through its steric and electronic factors, constrains the formyl group in a preferred conformation [1], the attack of any reagent on the arene ring or at the benzylic position, take place with a high degree of distereoselectivity [6].
