Enantioselective Iron/Bisquinolyldiamine Ligand-Catalyzed Oxidative Coupling Reaction of 2-Naphthols

Abstract

An iron-catalyzed asymmetric oxidative homo-coupling of 2-naphthols for the synthesis of 1,1′-Bi-2-naphthol (BINOL) derivatives is reported. The coupling reaction provides enantioenriched BINOLs in good yields (up to 99%) and moderate enantioselectivities (up to 81:19 er) using an iron-complex generated in situ from Fe(ClO4)2 and a bisquinolyldiamine ligand [(1R,2R)-N1,N2-di(quinolin-8-yl)cyclohexane-1,2-diamine, L1]. A number of ligands (L2–L8) and the analogs of L1, with various substituents and chiral backbones, were synthesized and examined in the oxidative coupling reactions.

Advances in the Asymmetric Synthesis of BINOL Derivatives

“…Che and co-workers introduced a chiral aminopyridine-like ligandbisquinolyldiamine [(1R,2R)-N 1 ,N 2 -di(quinolin-8-yl)cyclohexane-1,2-diamine (BQCN)]and applied it to the iron-catalyzed asymmetric cis-dihydroxylation of alkenes [67]. Inspired by this work, Liu's group [68] (Scheme 6) established a methodology for the asymmetric oxidative homo-coupling of 2-naphthols (3c), leading to the synthesis of (S)-BINOL derivatives (1) mediated by a Fe complex and generated in situ from Fe(ClO4)2 and the BQCN ligand. Excellent yields (up to 99%) and enantiomeric excesses (up to 81%) have been reported.…”

Advances in C(sp2)−H/C(sp2)−H Oxidative Coupling of (Hetero)arenes Using 3d Transition Metal Catalysts

“…The prolonged reaction time in some cases is a constraint for this protocol. Intriguingly, a phosphine‐free iron‐bisquinolyldiamine system was also successfully demonstrated to synthesize BINOL in up to 99% yield and moderate enantioselectivity [39] …”

Substituted Naphthols: Preparations, Applications, and Reactions

“…The presence of the naphthol moiety in these products plays an important role in their biological applications (Figure 1 highlights select examples of such natural and synthetic naphthol derivatives). Furthermore, naphthols have been used as building blocks in organic synthesis to access complex organic compounds [ 18–20 ] – some of the most recent applications have focused on the asymmetric oxidative homo‐coupling of 2‐naphthols to access BINOL derivatives using Iron [ 21 ] or Ruthenium catalysis, [ 22 ] or alternatively 2‐naphthols can undergo Nickel‐catalyzed allylic dearomatization reactions with allylic alcohols, [ 23 ] and even participate in Gold‐catalyzed hydroarylation reactions with terminal alkynes. [ 24 ]…”