Palladium‐Catalyzed Regioselective Aromatic Extension of Internal Alkynes through a Norbornene‐Controlled Reaction Sequence

Abstract

A regioselective aromatic π-extension reaction of internal alkynes is reported. The proposed method employs three easily available components, namely aryl halides, 2-haloarylcarboxylic acids, and disubstituted acetylenes. The transformation is driven by a controlled reaction sequence of C-H activation, decarboxylation, and annulation to give poly(hetero)aromatic compounds in a site-selective fashion. Unlike in previously reported palladium-catalyzed three-component annulations, alkyne carbopalladation is the last step of this tandem reaction.

Mechanistic Insights into the Ruthenium-Catalyzed [4 + 1] Annulation of Benzamides and Propargyl Alcohols by DFT Studies

“…One class of typical transition-metal-catalyzed intermolecular annulations have emerged widely with internal alkynes and aromatic compounds as coupling partners. The internal alkynes generally serve as two-carbon reaction partners but seldom as one-carbon reaction partners . Very recently, Zhou, Liu, and co-workers developed Ru-catalyzed redox-neutral [4 + 1] annulation of benzamides and propargyl alcohols, in which propargyl alcohol act as one-carbon units, as shown in Scheme .…”

Expedition to Phenanthrene Nucleus: A Two‐decade Research on Bench

“…A further β‐C elimination of NBE from E resulted in palladacycle F which in presence of alkyne follows reductive elimination to afford the desired products 15 (Scheme 39). [53] …”

α-Bromoacrylic Acids as C1 Insertion Units for Palladium-Catalyzed Decarboxylative Synthesis of Diverse Dibenzofulvenes

“…Recently, halogenated carboxylic acids have been employed as coupling reagents to form various polycyclic compounds by a palladium-catalyzed decarboxylative cyclization reaction (Scheme a). − The Kwong group first reported a palladium-catalyzed three-component decarboxylative cyclization to access polycyclic aromatic hydrocarbons by using o -bromobenzoic acids . Our group and Zhang have also developed some efficient methods to enrich the chemistry.…”

“…On the basis of our experimental results as well as previous work, − a plausible catalytic cycle for this protocol is depicted in Scheme . Initially, the oxidation addition of 2-iodobiphenyl 1a to Pd(0) species produces biphenylpalladium species A , which undergoes a C–H activation to give palladacycle B .…”