Efficient Synthesis of 2‐Methyl Derivatives of 1,1′‐Bi(2‐naphthol) and 1,1′‐Bi(2‐phenols)

Abstract

AbstractReaction of 1,1′‐binaphthol and structurally related 1,1′‐biphenols with sulfonylating reagents [RSO2Cl; R = 4‐Tol, Ph] leads to clean, ultraselective monoderivatisation, shown crystallographically in one case (2‐OH–2′‐OTs–1,1′‐binaphthyl). Reaction of the remaining 2‐hydroxy function with either Tf2O or NfF [Nf = nonaflate, CF3(CF2)3SO2‐] affords the protected/activated cores (2‐R1O–2′‐R2O–1,1′‐biaryl) [R1,R2 pairs = Tf,Ts (X‐ray); Tf,SO2Ph; Nf,Ts (on 1,1′‐binaphthyl core); Tf,Ts; Nf,Ts (on 1,1′‐biphenyl core); Tf,Ts; Nf,Ts (on 3,3′,5,5′‐tetramethyl‐1,1′‐biphenyl core)]. Reaction of the Tf,Ts species with either MeMgBr/NiCl2(dppe) (for the 1,1′‐binaphthyl) or (AlMe3)2(DABCO)/Pd2(dba)3 (for the 1,1′‐biphenyl) affords 2‐OH–2′‐Me–1,1′‐biaryl units on subsequent hydrolysis (crystallographically characterised in the binaphthyl case). The latter methyl/hydroxy compounds are doubly deprotonated by either nBuLi/TMEDA or nBuLi/tBuOK to afford dianions that react cleanly with Cl2SiPh2 (two X‐ray structures). The equivalent reaction of the 2‐OH–2′‐Me–1,1′‐binaphthyl with Ph(O)Cl2 is less clean due to the absence of a strong Thorpe–Ingold effect. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)