Desymmetrization of Symmetrical Triarylcarbinols: Synthesis of 7-Arylfluorenes and a C 2-Symmetric Chiral BIFOL Phosphoric AcidWe thank CSIR, New Delhi, and DST, New Delhi, India for financial support. This work has been supported by the Science and Engineering Research Board [Grant Number SR/S1/OC-04/2011(G)] and Council of Scientific and Industrial Research [Grant Number 02(0027)/11/EMR-II]. N.S. thanks the Council of Scientific and Industrial Research, New Delhi, for an SRF. M.K. thanks Pondicherry University for a fellowship.
Received: 27 April 2017
Accepted after revision: 20 June 2017
19 July 2017 (eFirst)
Dedicated to Prof. Takahiko Akiyama for his contribution in chiral phosphoric acid organocatalysis
A simple and an efficient method for the synthesis of 7-arylfluorenes by intramolecular cyclization of the corresponding triarylcarbinols in the presence of the solid-acid catalyst NaHSO4/SiO2 has been developed. By using this method, a new chiral diol with a C 2-symmetric bisfluorenyl unit, 7,7′-diphenyl-7H,7′H-5,5′-bibenzo[c]fluorene-6,6′-diol (BIFOL), having central chirality was synthesized in an optically active form from (S)-(–)-BINOL-3,3′-dicarboxylic acid. The absolute configuration of the chiral bisfluorene derivative BIFOL was ascertained by single-crystal X-ray analysis. Furthermore, a new chiral phosphoric acid was synthesized from BIFOL and evaluated for enantioselective transfer hydrogenation.