Nucleophilic additions to the chiral rhenium alkene complexes [Re(η 5 -C 5 H 5 )(NO)(PPh 3 )(H 2 C[double bond, length half m-dash]CHR)]BF 4 (R = H, Me, CH 2 CH 2 Me, Ph or CH 2 Ph): regio-, diastereo- and enantio-selectivities Academic Article uri icon

abstract

  • Reactions of alkene complexes [Re(η5-C5H5)(NO)(PPh3)(H 2C=CHR)]BF4 1 (R = H a, Me b, CH2CH2Me c, Ph d or CH2Ph e) and LiCuMe2 in tetrahydrofuran (thf) at -80°C gave the primary, β-branched alkyl complexes [Re(η5-C5H5)(NO)(PPh3)(CH 2CHMeR)] 2 (79-99%). No secondary alkyl complexes derived from additions to the unsubstituted =CH2 termini were detected. Product diastereomer and enantiomer ratios matched those of the reactants. Thus, the additions are regiospecific, diastereospecific and enantiospecific. A chemical correlation involving [Re(η5-C5H5)(NO)(PPh3){CH 2CH(CD3)Me}] and a crystal structure determination [(SR,RS)-2e·0.5C6H14] show that attack occurs on the C=C face anti to the rhenium. Reactions of 1a or 1b (in thf) with NaOMe-MeOH gave predominantly the 2-methoxyalkyl complexes [Re(η5-C5H5)(NO)(PPh3){CH 2CH(OMe)R}] (R = H 4a or Me 4b) (92-97%). Analogous reactions of 1c or 1d gave 81-77:19-23 mixtures of 4c or 4d and the alkenyl complexes (E)-[Re(η5-C5H5)(NO)(PPh 3)(CH=CHR)] (85-71%). A similar reaction of 1e gave mainly the allyl complex [Re(η5-C5H5)(NO)(PPh3)(CH 2CH=CHPh)].

author list (cited authors)

  • Peng, T., Arif, A. M., & Gladysz, J. A.

citation count

  • 10

publication date

  • January 1995