R. Pasch et al., PLANAR CHIRAL CP-ASTERISK-RU COMPLEXES .2. BIS(ALLYL) AND BIS(ARENE) COMPLEXES DERIVED FROM (R)-CARVONE, Organometallics, 16(18), 1997, pp. 3950-3958
Reaction of [CpRuOMe](2) (1) with either enantiomer of the naturally
occurring ketonic diterpene carvone or the trimethylsilyl enolate deri
ved thereof leads to homochiral CpRu-pi-complexes 6-9, where the Cp*R
u moiety is bound to either the exocyclic double bond or an allyl func
tion derived from it as well as to an enone or ene system in the ring.
Full aromatization of the cyclic enone under the same reaction condit
ions was achieved with 7,8-dihydrocarbone or its trimethylsilyl enolat
e, respectively, giving complexes 13 and 14. The carvacrole complex 14
(and consequently also 13) is shown by the NMR spectra of the diaster
oisomers obtained through derivatization with (S)-camphorsulfonic acid
to be homochiral, thus, central chirality of the carvone has been ful
ly transformed into planar chirality of the carvacrole complex. Compou
nds 6, 7 . BFB4 7 . CF3SO3, and 8 . CF3SO3, and 14 . CF3SO3 where char
acterized by single-crystal X-ray analysis, which allowed for the dete
rmination of the absolute configuration of the latter.