The π-basic metal fragment {MoTp(NO)(DMAP)} (where Tp = trispyrazolyl(borate) and DMAP = N,N-dimethylaminopyridine) can coordinate aromatic molecules and activate them toward addition reactions. This study focuses on how to carry out these addition reactions enantioselectively. Reduction of the racemic, aromatic precursor MoTp(NO)(DMAP)(I) in the presence of (R)-α-pinene yields a single diastereomer, (R,R)-MoTp(NO)(DMAP)(α-pinene) (ee ≥ 97%, 11 g scale). Exchange of the α-pinene ligand for a variety of other π-ligands (i.e., acetone, naphthalene, benzaldehyde, ethyl acetate, etc.) occurs with good yield, but loss of the enantioenrichment. In contrast, oxidation of (R,R)-MoTp(NO)(DMAP)(α-pinene) with iodine yields the resolved (S)-MoTp(NO)(DMAP)(I) (ee = 98%, 4.6 g scale). Reduction of this molybdenum(I) precursor results in enantioenriched molybdenum(0) complexes, including (R)-MoTp(NO)(DMAP)(η2-trifluorotoluene). Subjecting this arene complex to protonation, addition of a silylated enolate, and oxidative liberation of the organic with iodine, yields an enantioenriched 1-(trifluoromethyl)cyclohexa-1,3-diene organic (ee = 98%) while also recovering MoTp(NO)(DMAP)(I).

Studies toward enantioenriched molybdenum dearomatization

255th National Meeting (2018)

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