A general synthetic route to chiral dihydroxy-9,9′-spirobifluorenes |
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Authors: | Xu Cheng |
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Institution: | State Key Laboratory and Institute of Elemento-organic Chemistry, Nankai University, Tianjin 300071, China |
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Abstract: | C2-Symmetric 9,9′-spirobifluorenes with 2,2′-, 3,3′-, and 4,4′-dihydroxyls were conveniently prepared from 1,2-dibromobenzene. The palladium-catalyzed coupling reaction of 1,2-dibromobenzene with methoxyphenylmagnesium bromide or methoxyphenylboronic acid provided methoxy substituted 2-bromobiphenyls. Lithium-bromine exchange with n-butyllithium, followed by reaction with dimethyl carbonate afforded di2-(methoxyphenyl)phenyl]ketones as the key intermediates. A continuous ring-closure induced by a strong Lewis acid and demethylation gave dihydroxy-9,9′-spirobifluorenes. The racemic dihydroxy products were resolved by inclusion crystallization using chiral resolving reagents or separated by chiral HPLC. |
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Keywords: | Chiral spirobifluorene Suzuki coupling Kumada coupling Cyclization |
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