A method for the synthesis of sulfides from carboxylic acids via thioester C–S activation and acyl capture has been developed, wherein thioesters serve as dual electrophilic activators of carboxylic acids and S-nucleophiles through the merger of decarbonylative palladium catalysis and sulfur coupling. This new concept employs readily available carboxylic acids as coupling partners to directly intercept sulfur reagents via redox-neutral thioester-enabled cross-over thioetherification. The scope of this platform is demonstrated in the highly selective decarbonylative thioetherification of a variety of carboxylic acids and thioesters, including late-stage derivatization of pharmaceuticals and natural products. This method operates under mild, external base-free, and operationally practical conditions, providing a powerful new framework to unlock aryl electrophiles from carboxylic acids and increase the reactivity by employing common building blocks in organic synthesis.
more »
« less
Highly-chemoselective step-down reduction of carboxylic acids to aromatic hydrocarbons via palladium catalysis
Aryl carboxylic acids are among the most abundant substrates in chemical synthesis and represent a perfect example of a traceless directing group that is central to many processes in the preparation of pharmaceuticals, natural products and polymers. Herein, we describe a highly selective method for the direct step-down reduction of carboxylic acids to arenes, proceeding via well-defined Pd(0)/( ii ) catalytic cycle. The method shows a remarkably broad substrate scope, enabling to direct the classical acyl reduction towards selective decarbonylation by a redox-neutral mechanism. The utility of this reaction is highlighted in the direct defunctionalization of pharmaceuticals and natural products, and further emphasized in a range of traceless processes using removable carboxylic acids under mild, redox-neutral conditions orthogonal to protodecarboxylation. Extensive DFT computations were conducted to demonstrate preferred selectivity for the reversible oxidative addition and indicated that a versatile hydrogen atom transfer (HAT) pathway is operable.
more »
« less
- Award ID(s):
- 1650766
- NSF-PAR ID:
- 10146146
- Date Published:
- Journal Name:
- Chemical Science
- Volume:
- 10
- Issue:
- 22
- ISSN:
- 2041-6520
- Page Range / eLocation ID:
- 5736 to 5742
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
more » « less
Abstract Decarbonylative borylation of carboxylic acids is reported. Carbon electrophiles are generated directly after reagent‐enabled decarbonylation of the in situ accessible sterically‐hindered acyl derivative of a carboxylic acid under catalyst controlled conditions. The scope and the potential impact of this method are demonstrated in the selective borylation of a variety of aromatics (>50 examples). This strategy was used in the late‐stage derivatization of pharmaceuticals and natural products. Computations reveal the mechanistic details of the unprecedented C−O bond activation of carboxylic acids. By circumventing the challenging decarboxylation, this strategy provides a general synthetic platform to access arylpalladium species for a wide array of bond formations from abundant carboxylic acids. The study shows a powerful combination of experiment and computation to predict decarbonylation selectivity.
-
more » « less
Abstract Decarbonylative borylation of carboxylic acids is reported. Carbon electrophiles are generated directly after reagent‐enabled decarbonylation of the in situ accessible sterically‐hindered acyl derivative of a carboxylic acid under catalyst controlled conditions. The scope and the potential impact of this method are demonstrated in the selective borylation of a variety of aromatics (>50 examples). This strategy was used in the late‐stage derivatization of pharmaceuticals and natural products. Computations reveal the mechanistic details of the unprecedented C−O bond activation of carboxylic acids. By circumventing the challenging decarboxylation, this strategy provides a general synthetic platform to access arylpalladium species for a wide array of bond formations from abundant carboxylic acids. The study shows a powerful combination of experiment and computation to predict decarbonylation selectivity.
-
more » « less
Abstract A Rh(I)‐catalyzed C6‐selective C−H arylation of 2‐pyridones with inexpensive, readily available, safe and structurally diverse aryl carboxylic acids with the aid of a pyridine directing group is developed. This decarbonylative arylation protocol features an easy‐to‐handle catalytic system, and is amenable to diversely substituted 2‐pyridones and aryl carboxylic acids. It allows access to a wide range of C6‐arylated 2‐pyridones, including those that are difficult to prepare using conventional C−H arylation processes. The method tolerates various electron‐neutral, electron‐rich and electron‐deficient functional groups, and affords the products in 41–91% yields.
magnified image -
The α-acyloxylcarbonyl motif can be found in many important pharmaceuticals and biologically active natural products and their derivatives. In this manuscript, the direct synthesis of α-acyloxylketones from ketones and readily available carboxylic acids was realized using a photo-assisted halogen bond-mediated organocatalytic α-acyloxylation reaction. The desired α-acyloxylation products were obtained in good to high yields.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/c9sc00892f
