Arenechromium carbonyl

Kinetic resolution of ( )-(o-anisaldehyde)Cr(CO)s (1).1 This arenechromium carbonyl has been resolved by chromatography of a derivative, but a more convenient method involves reaction with L-valinol to form two imines (a, b) with widely different Rf values. The fastest moving fraction (a) is a precursor to (-)-l, whereas the slower moving fraction provides ( + )-l on hydrolysis. 

Dieneiron carbonyl and arenechromium carbonyl complexes in which the chirality is introduced by metal coordination and depends upon the structure of the complex. In these systems, the organometallic complex is destroyed in the cleavage reaction. 

Many other aminoalcohols and related compounds have been recommended as catalysts in enantioselective additions of organozinc reagents to aldehydes. Tri-carbonyl chromium complexation of the aryl ring of 1.14 (R = Me,n-Bu) can lead to improved enantioselectivities [1171], Other arenechromium carbonyl com-plexed aminoalcohols have also been proposed as Zn ligands [1172],... 

In addition to alkenes, arenes can sometimes be used as radical acceptors in Sml2-mediated carbonyl-alkene couplings. For example, Schmalz reported extensive studies on ketyl additions to arenechromium tricarbonyl complexes 66,67 tetralin-Cr(CO)3 complex 49 underwent reductive carbonyl addition to the aromatic ring upon treatment with Sml2 to furnish the skeleton of the naturally occurring aryl glycoside pseudopterosin G (Scheme 5.37).66,67 Here, the bulky metal tricarbonyl group not only serves to control the... 

Transition-metal-stabilized carbocations can be generated from functionalized butadieneiron carbonyl or arenechromium tricarbonyl complexes [92], Reactions of such carbocations formed from chiral complexes have been studied, but low selectivities are usually observed [526, 528, 535]. However, chromium tricarbonyl complexes derived from ephedrine 5.66 suffer cyclization in acidic medium. After decomplexation, c/s-tetrahydroquinolines are formed with a high diastereo-and enantioselectivity [540,542] (Figure 5.44). 

Arenechromium tricarbonyl benzaldehydes bearing a substituent in 2-position in order to fix the conformation of the carbonyl group also undergo highly selective silylcyanation with Me3SiCN. After decomplexation, precursors of ami-noalcohols are obtained with a high enantioselectivity [539] (Figure 6.27). 

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