Transition‐metal‐free regioselecitive C−H arylation of 2‐naphthols with diaryliodonium salts has been developed. The reaction proceeds under very simple experimental conditions and affords a range of products with various substitution patterns. The method allows for the incorporation of electron‐deficient aryls, which complements well currently existing metal‐free aryl–aryl cross‐couplings of phenols that have been so far restricted to the introduction of electron‐rich aryl moieties. The mechanism of the reaction was studied by means of DFT calculations, demonstrating that the C−C bond formation occurs via a dearomatization of 2‐naphthol substrate, followed by a subsequent rearomatization by tautomerization. The computations show that the use of a low polarity solvent and an insoluble inorganic base is key to securing the high selectivity of the C−C coupling over a competing C−O arylation pathway, by preventing the incipient deprotonation of 2‐naphthol.
Alkenes possessing four different carbon‐linked substituents are the main structural motif of many biologically active compounds. The derivatives of (2E)‐3‐(3‐methoxyphenyl)‐2‐methylpent‐2‐enoic acid ((E)‐2c) are suitable precursors for the synthesis of Tapentadol, a novel centrally acting analgesic. It was found that the Ni‐carbometallation reaction of disubstituted alkyne 8 with CO2 and an Et2Zn allows for efficient and practical preparation of (E)‐2c as a single (E)‐regioisomer in 89% of isolated yield. The influence of the size of the aliphatic substituent of alkyne and the steric hindrance of the organozinc reagent on stereochemical course of the carbometallation reaction was evaluated. Finally, air‐stable Ni(dme)Cl2 was proposed as an alternative to widely used Ni(cod)2 catalyst.
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