A novel axially dissymmetric chiral ligand based on amine N-oxide: (R)- and (S)-3,3′-dimethyl-2,2′-biquinoline N,N′-dioxide

Diastereo‐ and Enantioselective Reductive Aldol Reaction with Trichlorosilane Using Chiral Lewis Bases as Organocatalysts

“…Although structurally similar to BINAPO, (S)-SEGPHOSO was found to significantly lower the reactivity and selectivities (Table 1, entry 4). On the other hand, (R)-BQNO, a bisquinoline N,N'-dioxide developed in our laboratory [8] exhibited good activity and selectivity, while (R)-BIQNO, a bisisoquinoline N,N'-dioxide, [9] afforded low enantioselectivity (Table 1, entries 5 and 6). [10,11] Having discovered several effective catalysts, we next investigated the reductive aldol reaction of a variety of substrates ( Table 2).…”

Chiral N-Oxides as Catalysts or Ligands in Enantioselective Reactions

“…tert-Butyl ester resulted in the highest enantioselectivity of 84% ee (entry 5). The addition of acrolein confirmed the beneficial effect of tert-butyl ester (entry 6) and is a rare example of the catalytic enantioselective Michael addition of 5 …”

Chiral pyridine N-oxides: useful ligands for asymmetric catalysis

“…9 Racemic 2 was prepared by MCPBA oxidation of 3,3 0 -dimethyl-2,2 0 -biquinoline 1, in turn readily obtained from anthranilic acid in three steps and then resolved via the hydrogen-bonding complex with (S)-or (R)-binaphthol (Scheme 2). 10 Ligand (S)-4 was initially obtained enantiomerically pure by preparative high performance liquid chromatography (HPLC) using a chiral column from racemic 4, 11 which was prepared by N-oxidation of 1,1 0 -biisoquinoline 3. Next, the racemic dioxide 4 was successfully resolved via complexation with (R)-binaphthol (Scheme 3).…”