This Article describes the development of a base-free, nickel-catalyzed decarbonylative coupling of carboxylic acid fluorides with diboron reagents to selectively afford aryl boronate ester products. Detailed studies were conducted to assess the relative rates of direct transmetalation between aryl boronate esters and diboron reagents and a bisphosphine nickel(aryl)(fluoride) intermediate. These investigations revealed that diboron reagents undergo transmetalation with this Ni(aryl)(fluoride) intermediate at rates significantly faster than their aryl boronate ester congeners. Furthermore, the reactivity of both boron reagents toward transmetalation is enhanced with increasing electrophilicity of the boron center. These mechanistic insights were leveraged to develop a catalytic decarbonylative borylation of acid fluorides that proved applicable to a variety of (hetero)aryl carboxylic acid fluorides as well as diverse diboron reagents. The acid fluorides can be generated in situ directly from carboxylic acids. Furthermore, the mechanistic studies directed the identification of various airstable Ni pre-catalysts for this transformation.
A general procedure for the palladium-catalyzed carbonylative Sonogashira coupling of aryl bromides is reported, using near stoichiometric amounts of carbon monoxide. The method allows a broad substrate scope in moderate to excellent yields. The formed alkynone motive serves as a platform for synthesis of various heterocyclic structures, including pyrimidines. Furthermore, the presented strategy allows effective (13)C labeling.
A high‐yielding procedure for the synthesis of isatins has been developed. Sequential Pd‐catalyzed double carbonylation of 2‐iodoanilines with near stoichiometric amounts of CO followed by acid‐promoted cyclization readily affords an array of isatins. The conversion of 2‐iodoanilines to isatins in good to excellent yields was found to proceed with good functional group tolerance. This protocol proved adaptable to 13C‐isotope labeling of isatins, which was extended to the synthesis of the 13C‐isotope labeled antiviral drug metisazone and the experimental anti‐schizophrenia drug ML137.
29, 30b, and 31b, and the spectra were reprocessed and have been replaced in the revised Supporting Information.For compounds 10, 18b, 23, and 26b, the reactions were rerun and the new spectra have been provided in the corrected Supporting Information.For compound 5, the wrong spectra were submitted in the original Supporting Information. The correct spectra are now included in the revised Supporting Information.For compound 27, the original FID was not located, and new spectra were obtained and are provided in the revised Supporting Information.The spectra editing did not affect any of the conclusions of the published paper. The corrected yields based on the revised spectra are as follows: 10 (87% yield), 18b (98% yield), 23 (90% yield), and 26b (95% yield).
The Pd‐catalyzed double carbonylation of 2‐iodoanilines using nearly stoichiometric amounts of CO, generated ex situ from solid CO‐surrogate SilaCogen, followed by acid promoted cyclization of intermediates (IV) affords isatine derivatives.
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