Optical resolution and absolute configuration of the chiral pentamethylcyclopentadienylrhenium carbonyl complex [(η5-C5Me5)Re(NO)(PPh3)(CO)]+ BF4−
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Reaction of racemic ester (η5-C5Me5)Re(NO)(PPh3)(CO2CH3) and (-)-(S)-α-(1-naphthyl)ethylamine gives amide (η5-C5Me5)Re(NO)(PPh3)(CONHCH(CH3) C10H7) (3) as a (SS)-/(RS)- diastereomer mixture. Crystallization gives the less soluble diastereomer (-)-(RS)-3 (77%, ≥ 98% diastereomeric excess). Subsequent reaction with CF3CO2H and then NaBF4 gives carbonyl complex (-)-(R)-[(η5-C5Me5)Re(NO)(PPh3)(CO)]+ BF4- (91%, ≥ 99% enantiomeric excess), which is in turn reduced (Li(C2H5)3BH/BH3 · THF) to methyl complex (-)-(R)-(η5-C5Me5)Re(NO)(PPh3)(CH3) (97%). These serve as convenient precursors to a variety of other optically active complexes. Preparations of enantiomeric complexes, diastereomer (-)-(RR)-3, and recycling of the chiral α-(1-naphthyl)ethylamine auxilliary are also described. The structure and absolute configuration of (-)-(RS)-3 is verified crystallographically (orthorhombic, P212121 (no. 19), a 12.348(4), b 13.198(5), c 22.168(9) Å, Z = 4). © 1990.
author list (cited authors)
Huang, Y., Niedercorn, F., Arif, A. M., & Gladysz, J. A.