Axially Chiral 1,1'‐Binaphthyl‐2‐Carboxylic Acid (BINA‐Cox) as Ligands for Titanium‐Catalyzed Asymmetric Hydroalkoxylation

Abstract

Axially chiral, enantiopure 1,1′-binaphthyl-2-carboxylic acids (BINA-Cox) have recently been introduced as chiral ligands for transition metal catalysis. Together with equimolar, co-catalytic amounts of Ti(OiPr) 4 and water they form an in situ catalyst that performs the asymmetric catalytic hydroalkoxylation of 2-allylphenols to 2-methylcoumarans at high temperature (240°C, microwave heating). The synthesis of reference ligand 2′-MeO-BINA-Cox (L1) has been optimized and performed at molar scale. Synthetic routes have been developed to access a variety of substituted BINA-Cox ligands (>30 exam- [a]

Dimenthylphosphine P-Oxide as a Synthetic Platform for Bulky and Chiral Ligands with Dimenthylphosphino Donor Groups

“…Chemicals and solvents were obtained commercially and used without purification if not otherwise mentioned. PdCl 2 (MeCN) 2 , 1-bromo-2-methoxynaphthalene, and 2-bromo-2′,6′-dimethoxybiphenyl ( 23 ) were synthesized according to literature procedures. Solvents were dried by filtering over activated Al 2 O 3 and storing under argon over molecular sieves (3 Å).…”

Chiral Carboxylic Acid Assisted Enantioselective C–H Activation with Achiral CpxMIII (M = Co, Rh, Ir) Catalysts

“…With the readily available optically active BINOL ( 5 ) as the starting material, transition-metal-catalyzed coupling technologies and carboxylate-directed C–H functionalization would enable access to various CCAs, providing different steric and electronic effects (Figure ). While C 2 -symmetric binaphthyl dicarboxylic acids had been studied as chiral organocatalysts by Hashimoto and Maruoka, the investigation of such axially chiral C 1 -symmetric monocarboxylic acids in asymmetric catalysis was quite limited …”

Catalytic Asymmetric Hydroalkoxylation of C–C Multiple Bonds

“…Recent efforts by the authors have focused on expanding the limited reactivity scope by preparing and testing a diverse library of BINA–Cox ligands (>30). 170 While incremental improvements to the substrate scope were achieved, this method has so far not been successfully applied to aliphatic alkenols. The authors suggest that a multinuclear titanium-μ-oxo species is in situ generated and acts as the active catalytic species, although they have not yet confirmed the structure of the formed complex.…”

“…Recent efforts by the authors have focused on expanding the limited reactivity scope by preparing and testing a diverse library of BINA–Cox ligands (>30) . While incremental improvements to the substrate scope were achieved, this method has so far not been successfully applied to aliphatic alkenols.…”