Reductive-Delay Heck 1,1-Diarylation of Terminal Alkenes

Abstract

Pd-catalyzed chemo- and regiocontrollable 1,1-diarylation of unactivated aliphatic alkenes with two aryl halides was developed. Under the cationic reductive-delay Heck pathway, the first aryl insertion is followed by β-H elimination, while the second aryl insertion is terminated by C–H bond formation.

On the Topic of Substrate Scope

“…An additional table of all other unreactive substrates attempted (eight examples) is listed in the Supporting Information in Scheme S1. Further examples published at Organic Letters within the past month, where the scope has largely been selected to provide the most information with fewer examples, typically illustrate 26–29 substrate combinations. − …”

Palladium Catalysis: Dependence of the Efficiency of C−C Bond Formation on Carboxylate Ligand and Alkali Metal Carboxylate or Carboxylic Acid Additive. Part C: The Domino Diarylation and Annelation Reactions

“…[11] . The promoting effect of alcohols on halide dissociation of neutral arylpalladium halide complexes via hydrogen‐bonding was already known, [12] but the no‐formation of 2a1 under acid‐free conditions led the authors to assume collaborative assistance of suitable carboxylic acids [10] …”

“…[9] In contrast to the published Z-configuration, we draw 2bC with E-structure as usually observed for β-H elimination leading to disubstituted olefins.. [11] The promoting effect of alcohols on halide dissociation of neutral arylpalladium halide complexes via hydrogen-bonding was already known, [12] but the no-formation of 2a1 under acid-free conditions led the authors to assume collaborative assistance of suitable carboxylic acids. [10] In 2022, Wu and co-workers disclosed a domino reaction involving successively Heck and reductive Heck phenylation of N-(quinolin-8-yl)pent-4-enamide 2 a leading to 2a1 in 89% yield when performed with phenyl bromide, (η 3 -allyl)PdCl 2 /1,1'-(oxydi-2,1-phenylene)bis[1,1-diphenylphosphine oxide] (DPEPO) as the catalyst system, lithium methoxide and para-hydroxybenzoic acid in 2,3-butanediol at 130 °C, while no reaction arose under either basefree or acid-free conditions (Scheme 2a). [10] Yield and selectivity were very sensitive to the experimental conditions.…”

“…[10] In 2022, Wu and co-workers disclosed a domino reaction involving successively Heck and reductive Heck phenylation of N-(quinolin-8-yl)pent-4-enamide 2 a leading to 2a1 in 89% yield when performed with phenyl bromide, (η 3 -allyl)PdCl 2 /1,1'-(oxydi-2,1-phenylene)bis[1,1-diphenylphosphine oxide] (DPEPO) as the catalyst system, lithium methoxide and para-hydroxybenzoic acid in 2,3-butanediol at 130 °C, while no reaction arose under either basefree or acid-free conditions (Scheme 2a). [10] Yield and selectivity were very sensitive to the experimental conditions. While no more than 6% of a mixture of no-regioselective Heck and reductive Heck arylation compounds were identified as byproducts under the above conditions, changing Pd source, ligand, base, carboxylic acid or solvent led, in most cases, to strong increase of their amount with drop of 2a1 yield.…”

Regioselective and Geometrically Controlled Heck 1,1-Diarylation of Unactivated Aliphatic Alkenes

“…Based on our mechanistic investigations, ,− the main steps in a catalytic cycle for the Heck diarylation are proposed in Scheme . Initially, oxidative addition to aryl bromide occurred on the active LPd 0 catalyst of Cy-JohnPhos.…”