Synthesis of Condensed Heteroaromatic Compounds by Palladium-Catalyzed Oxidative Coupling of Heteroarene Carboxylic Acids with Alkynes

Abstract

The palladium-catalyzed oxidative coupling of indole-3-carboxylic acids with alkynes effectively proceeds in a 1:2 manner accompanied by decarboxylation to produce the corresponding 1,2,3,4-tetrasubstituted carbazoles, some of which exhibit solid-state fluorescence. Pyrrole-, benzofuran-, and furancarboxylic acids also undergo the decarboxylative coupling to afford highly substituted indole, dibenzofuran, and benzofuran derivatives, respectively.

A Highly Efficient Palladium‐Catalyzed Decarboxylative ortho‐Acylation of Azobenzenes with α‐Oxocarboxylic Acids: Direct Access to Acylated Azo Compounds

“…Since then, significant progress has been made on decarboxylative cross‐coupling reactions 3. For example, Goossen,3a–d Forgione,3e Li,3f Liu,3g,h Miura,3i Lee,3j and Tunge3k,l have studied decarboxylative biaryl coupling, olefination, alkynylation, aryl ketone formation and so forth. Very recently, Ge,4 Duan,5 Kim,6 Tan,7 Zhu,8 and Saxena9 have further demonstrated the feasiblity of decarboxylative acylation of arenes and other substrates by Pd‐catalyzed group‐directed CH activation.…”

Removable Directing Groups in Organic Synthesis and Catalysis

“…In this case, highly regioselective alkenylation with acrylic esters occurred in the 3-position. [13] 2-Pyrazol-5-yl-aniline (pzaH 2 ) has been used as an easily attachable and detachable directing group for the ortho CÀH functionalization of organoboronic acids (Scheme 9). Scheme 3.…”

“…[1] The term effective molarity (EM) has been defined (EM = k intra /k inter ) to describe and quantify this phenomenon. In enzyme catalysis, EM values between 10 5 to 10 8 m are frequently observed, but values up to 10 13 have been reached in extreme cases. Thus, an EM corresponds to a theoretical concentration of a reagent that would be required to render the bimolecular reaction as fast as the intramolecular process.…”

Efficient Pd‐Catalyzed Allene Synthesis from Alkynes and Aryl Bromides through an Intramolecular Base‐Assisted Deprotonation (iBAD) Mechanism

“…[9] Nevertheless, replacing the -OMe group by a -OTBDMS or -OTHP moiety permitted access to more advantageous allene products (2 t and 2 u). Whereas the reaction worked well with symmetrical dialkylated acetylene 2 m-u, we were not able to extend it to terminal alkynes, which underwent Sonogashira type reaction instead.…”