Diastereoselective 1,2 Additions of Nucleophiles to Quinoline Complexes of the Chiral Rhenium Lewis Acid [(.eta.5-C5H5)Re(NO)(PPh3)]+
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The racemic or optically active quinoline complexes [(η5-C5H5)Re(NO)(PPh3)NC9H7)+TfO− (1) and RLi (R = (a) CH2Si(CH3)3, (b) CH3, (c) C6H5) rapidly react in THF at −80 °C to give the 1,2 addition products (η5-C5H5)Re(NO)(PPh3)(NCH(R)CH=CHC(CH)4C), which contain new carbon stereocenters. Under optimum conditions, diastereoselectivities are ≥92%. Subsequent reactions with HOTf give mixtures of amine complexes (3) and alkene complexes (4) of the formulas [(η5-C5H5)Re(NO)(PPh3)(NHCH(R)CH=CHC(CH)4C]+TfO−. The latter dominate at equilibrium. The crystal structure of 4c establishes the carbon configurations, which are consistent with RLi attack from a direction anti to the bulky PPh3 ligand in 1. Reaction of (S)-1 and (CH3)2CHMgCl at −80 °C gives the 1,4 addition product (η5-C5H5)Re(NO)(PPh3)(NCH=CHCH(CH(CH3)2)C(CH)4C) as a 66:34 mixture of diastereomers. Reaction with HOTf gives the imine complex [(η5-C5H5)Re(NO)(PPh3)(N=CHCH2CH(CH(CH3)2C(CH)4C)]+TfO−. Stereochemical features of the preceding compounds and transformations are analyzed in detail. © 1994, American Chemical Society. All rights reserved.
author list (cited authors)
Stark, G. A., Arif, A. M., & Gladysz, J. A.