Cu^I/Ag^I‐Promoted Decarboxylative Alkynylation of ortho‐Nitro Benzoic Acids

Abstract

We report herein, a novel copper‐silver‐promoted alkynylation of ortho‐nitrobenzoic acids with arylacetylenic acids through a double decarboxylation. The present cross‐coupling is extremely challanging due to sluggish decarboxylation of arene carboxylates and deleterious oxidative Glaser‐Hay type homocoupling of terminal alkynes. Mechanistically, this sp2‐sp cross‐coupling may proceed through a silver‐assisted decarboxylation of 2‐nitrobenzoic acids followed by transmetalation with copper‐acetylide and reductive elimination. The ortho‐nitroacetylenic product is an important precursor for the synthesis of functionalized indoles.

Photoredox‐Catalyzed Tandem Demethylation of N,N‐Dimethyl Anilines Followed by Amidation with α‐Keto or Alkynyl Carboxylic Acids

“…Unless otherwise stated, all commercial reagents were used without additional purification. The starting materials α‐oxocarboxylic acid; alkynyl carboxylic acid; and metal‐photocatalysts were prepared using literature reported method.…”

Recent Advances in Decarboxylative Reactions of Alkynoic Acids

“…Cu(I)/Ag(I)-mediated double decarboxylative coupling of o-nitrobenzoic acids and arylpropynoic acids to give 1aryl-2-(2-nitrophenyl)acetylenes was reported in 2018 by the Jana group (Scheme 22). 27 Mechanistically it is proposed that an arylsilver complex, generated via the decarboxylation of o-nitrobenzoic acid, and an arylethynylcopper complex, generated via decarboxylation of arylpropynoic acid, react through transmetalation to form an aryl(arylethynyl)copper complex. Finally, the 1-aryl-2-(2-nitrophenyl)acetylenes were formed through reductive elimination.…”

Palladium-Catalyzed Decarbonylative Sonogashira Coupling of Terminal Alkynes with Carboxylic Acids

“…During the past decades, great progress has been made. As for the synthesis of internal alkynes, decarboxylative coupling has been achieved by Su, Tan, and Jana dependently (Scheme C); however, the three reactions were conducted under the oxidative conditions with the use of NBS, dioxygen and Ag 2 CO 3 /CuI as the oxidant, which also lead to the production of byproduct 1,3-diynes through homocoupling of terminal alkynes. In addition, steric and (or) electron-deficient carboxylic acids were required in order to facilitate the decarboxylation.…”

“…Herein, we reported a redox-neutral reaction of carboxylic acids with terminal alkynes through decarbonylative coupling . This reaction overcame those issues such as the use of overstoichiometric oxidants, homocouplings of terminal alkynes, and the narrow substrate scope of carboxylic acids encountered in the oxidative decarboxylative couplings. − High tolerance of functional groups was also demonstrated, i.e., alkyl, MeO, CF 3 O, TMS, F, Cl, CF 3 , CN, carbonyl, sulfonamide, and heterocycles all survived well under the reaction conditions. These advantages are also the embodiment of sustainable chemical principles …”

“…Notably, compared with the oxidative decarboxylative alkynylation, − the scope of carboxylic acids was also rather general. Both electron-rich and electron-deficient benzoic acids underwent decarbonylative coupling with terminal alkynes under the similar reaction conditions.…”