Access to 2′-Substituted Binaphthyl Monoalcohols via Complementary Nickel-Catalyzed Kumada Coupling Reactions under Mild Conditions: Key Role of a P,O Ligand

Abstract

Two complementary Kumada coupling methods for the conversion of monotriflated 1,1'-binaphthalene-2,2'-diol (BINOL) into 2'-substituted binaphthyl monoalcohols under mild conditions are reported. A protocol using NiCl2(dppe), in combination with an improved preparation of the monotriflate, is effective for 1,1'-binaphthalene-2-ols containing unsubstituted or electron-poor aryl or benzyl 2'-substituents. An alternative procedure, using a potentially hemilabile-bidentate phosphinan-4-ol ligand, is superior for products containing neopentyl or electron-rich aryl 2'-substituents. The obtained binaphthyl alcohols represent potentially useful synthons for chiral ligands and auxiliaries.

Competing amination and C–H arylation pathways in Pd/xantphos-catalyzed transformations of binaphthyl triflates: switchable routes to chiral amines and helicene derivatives

“…Binaphthyl alcohols 1a-k and 7a/7b were prepared by published procedures 26 or modifications thereof (see the ESI †) starting from (R)-BINOL (>99%), which was purchased from Chem-Impex International, Inc and checked for optical purity prior to reaction. For development of chiral HPLC separation conditions used for confirmation of enantiomeric purity, racemic samples of 3a-j and 6a-j were prepared from commercial rac-BINOL using methods identical to those for the enantiopure products.…”

“…We recently reported synthetic routes to a series of 1,1′binaphthalene-2-ols bearing various aryl, alkyl, and benzyl substituents in the 2′-position (1a-j, Scheme 2). 26 These were envisioned as precursors for chiral carbene ligands in which steric and/or noncovalent interactions of the binaphthyl 2′-substituent could be tuned, providing potential benefits in enantioselective catalysis. 19 Naphthols 1a-j were readily converted into the corresponding triflates 2a-j by a modification of literature procedures (Scheme 2), 26,27 providing a starting point for further derivatization via Pd-catalyzed amination.…”

“…An interesting outcome was observed in catalytic reactions of 1,1′:2′,1″-ternaphthyl 2-triflate 8 (Scheme 4), which was prepared from alcohol precursor 7 by the same procedures used to obtain 1a-j (ref. 26) and 2a-j (Scheme 1). Compounds 7 and 8 exist as 50 : 50 mixtures of two diastereomers (7a/7b and 8a/8b) due to the adoption of two different atropisomeric orientations of the 2′-(1″-naphthyl) group about the second chiral axis.…”

Redox activity of a dissymmetric ligand bridging divalent ytter-bium and reactive nickel fragments

“…Particularly, LX-type ligands are widely used in Nickel-catalysed cross-coupling reactions to enhance catalytic efficiency. [30][31][32][33] They are considered to allow significantly facile activation of unreactive carbon-halogen bonds. 34 Inspired by recent work by Diao and co-workers which highlighted the complexity of high-valent nickel-mediated sp 3 -sp 3 and sp 2 -sp 2 C-C bond formation using spectroscopic and computational methods, 35 we thought that imidazole-based linkers, such as 2-pyrimidin-2-yl-1H-benzimidazole, namely Hbimpm, 36 would be good candidates to construct original bimetallic Ln-TM complexes and study the electronic modulation within these systems.…”

NOBIN-based chiral phosphite-type ligands and their application in asymmetric catalysis

“…Synthesis of ligands 2, (R a ,R a )-3 and (R a ,S a )-3.Starting from (R a )-or (S a )-BINOL, both enantiomers of N-Bn-NOBIN ((R a )-1 and (S a )-1)) were readily prepared following known methodology 36,37,54,55. With these enantiomers in hand, P*-monodentate diamidophosphite 2 as well as P,N-containing phosphites (R a ,R a )-3 and(R a ,S a )-3 were prepared in a single-step (Scheme 1).…”