The nickel-catalyzed cross-coupling reactions of neopentyl arenesulfonates with arylmagnesium bromides, involving nucleophilic aromatic substitution of alkyloxysulfonyl groups by aryl nucleophiles, take place in high yields. Optimal efficiencies are obtained by adding 3 + 2 equiv of the Grignard reagent to a mixture of dppfNiCl(2) and the sulfonate in refluxing THF. Neopentyl arenesulfonates are useful sources of the electrophilic aryl groups in these transition metal-catalyzed cross-coupling reactions. Aryl sulfonates are inappropriate due to their ambident reactivity under the reaction conditions. This new cross-coupling reaction can be used for the creative elimination of alkyloxysulfonyl groups from aromatic compounds and for the preparation of unsymmetric terphenyls and oligophenyls.
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Polyphenyl derivatives
Polyphenyl derivatives Q 0700Nickel(0)-Catalyzed Cross-Coupling of Alkyl Arenesulfonates with Aryl Grignard Reagents. -Nickel(0)-catalyzed cross coupling of neopentyl arenesulfonates (I) and (IV) with aryl Grignard reagents (II) affords unsymmetrically substituted biphenyl derivatives (III) and (V) in moderate to high yields. The reaction involves a nucleophilic aromatic substitution of the alkyloxysulfonyl group in compounds (I) and (IV) by an aryl ring. Even terphenyl derivatives (VI) are isolated in some cases due to a further substitution reaction. This method can be extended to a vinyl Grignard reagent (VII). Aryl arenesulfonates (IX), however, are less suitable substrates in the reaction with aryl Grignard reagents, since both the Caryl-O and the Caryl-S bond can be attacked by the nucleophile, providing access to mixtures of biphenyl derivatives (X) andXI). -(CHO, C.-H.; YUN, H.-S.; PARK*, K.; J.
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