1-Arylfluorenols: Convenient preparation via the ester-mediated nucleophilic aromatic substitution protocol, facile racemization, and intrinsic chiral induction ability

Novel 1-aryl-9H-fluoren-9-ols 1 were conveniently synthesized by using the ester-mediated nucleophilic aromatic substitution on 2,6- dimethoxybenzoate 2 by aryl Grignard reagents as the key step. Racemic 1- phenylfluorenol 1a was converted to the diastereomeric esters 8 of (S)-2'- methoxy-1,1'-binaphthyl-2-carboxylic acid, which were readily separable by silica-gel column chromatography. Reduction of the optically pure diastereomer (+)-8 with LiAlH₄ accompanied an appreciable racemization to give (+)-1a of 89% ee, which provides the first isolation of an optically active fluorenol of defined enantiomeric purity. Intrinsic chiral induction abilities of the 9-fluorenols 1 were examined in the atrolactic acid synthesis from phenylglyoxylates 9 and methylmagnesium iodide with diastereoselectivity of up to 85% de and the binaphthyl coupling of 1- methoxy-2-naphthoates 11 with 2-methoxy-1-naphthylmagnesium bromide with up to 73% de.