Palladium‐Catalyzed Catellani ortho‐Acylation Reaction: An Efficient and Regiospecific Synthesis of Diaryl Ketones

Abstract

A palladium-catalyzed, norbornene-mediated Catellani ortho-acylation reaction was developed by the use of either acyl chlorides or acid anhydrides as acylation reagents. The addition of more than a stoichiometric amount of H2 O is crucial for this transformation when acid chlorides are used, and kinetic studies indicate that the active acylation reagent is possibly an acid anhydride.

Ligand-Promoted meta-C–H Amination and Alkynylation

“…The lack of precedents using alkynyl coupling partners as electrophiles in the Catellani reaction also attests to the challenge of developing meta -C‒H alkynylation using norbornene as a transient mediator. 8 Encouraged by the success of meta -C‒H amination reactions using norbornene as transient mediator, we envisioned that meta -alkynylation could be achieved through a Pd(II)/Pd(IV) process using an alkynyl bromide as the electrophile. To our great delight, 25% yield of the meta -alkynylated product 10a was obtained, accompanied by 14% yield of the ortho -alkynylated product 10a’ in the presence of 10 mol% Pd(OAc) 2 , 20 mol% ligand L9 , alkynyl bromide 9 (2.0 equiv.…”

“…4 More recently, our group 7a and Dong’s group 7b have utilized directed ortho -palladation to achieve meta -C–H activation reactions 7 by synchronizing the palladacycle intermediate with Catellani’s norbornene-mediated relay process (Figure 1a). 8 Owing to the development of improved norbornene mediators and ligands, the scope of meta -C–H arylation and alkylation using this approach has been substantially expanded. 7c,7e In principle, this approach should be compatible with any substrate containing an effective ortho -directing group, thus rendering this approach potentially broadly applicable.…”

“…To date, ortho -C–H alkynylation has not been demonstrated in the Catellani type reactions. 8 Key to the success of these transformations is use of a modified norbornene and mono-protected 3-amino-2-hydroxy pyridine ligands. These results indicate that a transient mediator can be used in combination with the proper ligand and palladium catalyst to achieve a broad range of meta -C–H functionalization reactions that are rich with diversity in both substrate and transformation.…”

Synthesis of Polysubstituted Pyridines and Indoles by a Palladium‐Catalyzed Catellani‐type Alkylation‐Alkenylation Sequence

“…Since then, Catellani, Lautens and other scientists enriched this chemistry significantly, making this methodology a reliable part of the toolbox for the synthesis of polysubstituted arenes. The ortho‐ position C−H functionalization of aryl halides includes alkylation, arylation, amination, and acylation . Ipso ‐position can be introduced with a variety of functional groups through C−C, C−H, C−N, C−O, or C−B coupling .…”

“…The ortho-position CÀ H functionalization of aryl halides includes alkylation, [12] arylation, [13] amination, [14] and acylation. [15][16][17] Ipso-position can be introduced with a variety of functional groups through C À C, C À H, C À N, C À O, or C À B coupling. [18] Since CÀ H functionalization of heterocycles is quite important, we attempt to link the Catellani reaction to the heterocycles.…”