Enantioselective Oxidative Coupling of 2‐Naphthol Derivatives by Copper‐(R)‐1,1′‐Binaphthyl‐2,2′‐diamine‐TEMPO Catalyst

Abstract

An efficient chiral copper catalytic system [(R)‐(+)‐1,1′‐binaphthyl‐2,2′‐diamine‐copper(I) chloride‐TEMPO] for the asymmetric oxidative coupling of 2‐naphthol derivatives to synthesize enantiomerically enriched BINOL derivatives has been developed with good to excellent enantiomeric excess (up to 97% ee). The addition of a catalytic quantity of 2,2,6,6‐tetramethylpiperidin‐1‐yl oxyl (TEMPO) to the copper‐(R)‐(+)‐1,1′‐binaphthyl‐2,2′‐diamine complex greatly enhanced the reactivity and enantioselectivity of the enantioselective oxidative coupling of 2‐naphthol derivatives and also reduced the reaction temperature from 90 °C to room temperature in dichloromethane solvent.magnified image

Aerobic oxidation catalysis with stable radicals

“…34). 128 In this study it was found that the reaction could proceed with just the (R)-BINAM-CuCl catalyst (where BINAM = 1,1 0 -binaphthyl-2,2 0diamine), but the addition of TEMPO significantly improved the reactivity, enabling these reactions to be carried out at room temperature (rather than 90 1C) in shorter reaction times (2-4 days rather than 7-9 days). A range of 1,1 0 -binaphthol derivatives were prepared in good to excellent yields (77-98%) with enantioselectivities up to 97% ee (depending on the substituents).…”

Enantioselective Total Synthesis of Secalonic Acid E

“…Thus, treatment of 16 with vanadium‐salan complex (10 mol %), Yb(OTf) 2 (5 mol %) in PhCl under oxygen atmosphere at 80 °C only led to decomposition of starting material 17. On the other hand, when 16 was treated with CuCl (5 mol %), BINAM (10 mol %), and TEMPO (10 mol %) under oxygen at RT no product formation was observed 18. We then decided to use a procedure, which we had developed for the synthesis of paecilin A ( 3 ) 12.…”

“…[17] On the other hand, when 16 was treated with CuCl (5 mol %), BINAM (10 mol %), and TEMPO (10 mol %) under oxygen at RT no product formation was observed. [18] We then decided to use ap rocedure, which we had developedf or the synthesis of paecilin A(3). [12] First we protected the enol moiety by formation of an enol methyl ether using trimethyl silyl diazomethane in dichloromethane and methanol at room temperature to give 17 a and 17 b in 71 %y ield in a1:2.4 ratio, which were separated by flash chromatography on silica gel (Scheme 5).…”

Recent advances and new concepts for the synthesis of axially stereoenriched biaryls

“…4 Finally, the homocoupling of 2naphthols bearing carbonyl-substituents at the C3-position using molecular oxygen as terminal oxidant and a catalytic amount of TEMPO (2,2,6,6-tetramethylpiperidin-1-yl oxyl) as a co-catalyst was promoted with a moderate to good atroposelectivity by the Cu/BINAM 3 catalytic system. 5 Importantly, the Cu-catalyzed synthesis of (S)-bisoranjidiol 6a and V-catalyzed synthesis of pigmentosin A and talaroderxines A and B6 b illustrate the synthetic utility of such asymmetric oxidative homocouplings.…”