NUCLEOPHILIC ADDITIONS TO THE CHIRAL RHENIUM ALKENE COMPLEXES [RE(ETA(5)-C5H5)(NO)(PPH(3))(H2C=CHR)]BF4 (R=H, ME, CH(2)CH(2)ME, PH OR CH(2)PH) - REGIO-SELECTIVITIES, DEASTEREO-SELECTIVITIES AND ENANTIO-SELECTIVITIES
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abstract
Reactions of alkene complexes [Re(5-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 -80C gave the primary, -branched alkyl complexes [Re(5-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(5-C5H5)(NO)(PPh3){CH 2CH(CD3)Me}] and a crystal structure determination [(SR,RS)-2e0.5C6H14] 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(5-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(5-C5H5)(NO)(PPh 3)(CH=CHR)] (85-71%). A similar reaction of 1e gave mainly the allyl complex [Re(5-C5H5)(NO)(PPh3)(CH 2CH=CHPh)].
