Synthesis of Polycyclic Heterocycles via a One-Pot Ortho Alkylation/Direct Heteroarylation Sequence

A practical ortho-acylation of aryl iodides enabled by moisture-insensitive activated esters via palladium/norbornene catalysis

Herein reported is a practical Catellani-type ortho-acylation of aryl iodides enabled by employing moisture-insensitive esters as the electrophile via C(O)–O bond cleavage.

Palladium/Norbornene Cooperative Catalysis

Palladium/norbornene cooperative catalysis has emerged as a distinct approach to construct polyfunctionalized arenes from readily available starting materials. This Review provides a comprehensive overview of this field, including the early stoichiometric investigations, catalytic reaction developments, as well as the applications in the syntheses of bioactive compounds and polymers. The section of catalytic reactions is divided into two parts according to the reaction initiation mode: Pd(0)-initiated reactions and Pd(II)-initiated reactions.

Synthesis of polyfluoroarene-substituted benzofuran derivatives via cooperative Pd/Cu catalysis

A cooperative Pd/Cu-catalyzed dual C–H bond activation of electron-deficient polyfluoroarenes with aryl halides is developed.

A metal-free cascade reaction of β-halo-α,β-unsaturated aldehydes and 1,4-dithiane-2,5-diols: synthesis of polycyclic 2-formylthiophenes

A cascade reaction of β-halo-α,β-unsaturated aldehydes and 1,4-dithiane-2,5-diols for the synthesis of 2-formylthiophenes has been described employing a polymer supported organic base.

Pd-catalyzed regioselective intramolecular direct arylation of 3-indolecarboxamides: access to spiro-indoline-3,3′-oxindoles and 5,11-dihydro-6H-indolo[3,2-c]quinolin-6-ones

We report regioselective intramolecular direct C-3 and C-2 arylations of the indole rings of 3-indolecarboxamides for diastereospecific production of spiro-indoline-3,3′-oxindoles and 5,11-dihydro-6H-indolo[3,2-c]quinolin-6-ones, respectively, under different reaction conditions.

Mechanism of Pd-catalyzed acylation/alkenylation of aryl iodide: a DFT study

The detailed mechanism of the Pd(0)-catalyzed cross-coupling of aryl iodide, benzoic anhydride and ethyl acrylate was clarified by theoretical methods.

Pd/norbornene-catalyzed sequential ortho-C–H alkylation and ipso-alkynylation: a 1,1-dimethyl-2-alkynol strategy

A palladium/norbornene-catalyzedortho-C–H alkylation andipso-alkynylation reaction for the synthesis of 2-alkyl-1-alkynyl arenes was reported, where the use of bulky 1,1-dimethyl-2-alkynols led to significant suppression of the formation ofO-alkylation and norbornene alkynylation by-products.

The mechanism of catalytic methylation of 2-phenylpyridine using di-tert-butyl peroxide

The mechanism of palladium chloride-catalyzed direct methylation of arenes with peroxides is elucidated by using the energetics computed at the M06 density functional theory. The introduction of a methyl group by tert-butyl peroxides at the ortho-position of a prototypical 2-phenyl pyridine, a commonly used substrate in directed C-H functionalization reactions, is examined in detail by identifying the key intermediates and transition states involved in the reaction sequence. Different possibilities that differ in terms of the site of catalyst coordination with the substrate and the ensuing mechanism are presented. The important mechanistic events involved are (a) an oxidative or a homolytic cleavage of the peroxide O-O bond, (b) C-H bond activation, (c) C-C bond activation, and (d) reductive elimination involving methyl transfer to the aromatic ring. We have examined both radical and non-radical pathways. In the non-radical pathway, the lowest energy pathway involves C-H bond activation prior to the coordination of the peroxide to palladium, which is subsequently followed by the O-O bond cleavage of the peroxide and the C-C bond activation. Reductive elimination in the resulting intermediate leads to the vital C-C bond formation between methyl and aryl carbon atoms. In the non-radical pathway, the C-C bond activation is higher in energy and has been identified as the rate-limiting step of this reaction. In the radical pathway, however, the activation barrier for the C-C bond cleavage is lower than for the peroxide O-O bond cleavage. A combination of a radical pathway up to the formation of a palladium methyl intermediate and a subsequent non-radical pathway has been identified as the most favored pathway for the title reaction. The predicted mechanism is in good agreement with the experimental observations on PdCl2 catalyzed methylation of 2-phenyl pyridine using tert-butyl peroxide.

Syntheses of indolizinones from an intramolecular one-pot process of gem-dibromoolefins

A rare type of indolizinone is constructed from an Intramolecular one-pot process from gem-dibromoolefins.

Extending the utility of [Pd(NHC)(cinnamyl)Cl] precatalysts: Direct arylation of heterocycles

The use of [Pd(NHC)(cinnamyl)Cl] precatalysts in the direct arylation of heterocycles has been investigated. Among four different precatalysts, [Pd(SIPr)(cinnamyl)Cl] proved to be the most efficient promoter of the reaction. The C–H functionalization of sulfur- or nitrogen-containing heterocycles has been achieved at low catalyst loadings. These catalyst charges range from 0.1 to 0.01 mol % palladium.

Pd-catalyzed C-H bond functionalization on the indole and pyrrole nucleus

This review details recent developments in the Pd-catalyzed C-H bond arylation and alkenylation of indoles and pyrroles, aromatic heterocycles that are frequently displayed in natural products and medicinal agents.

Direct transition metal-catalyzed functionalization of heteroaromatic compounds

During the last two decades there has been considerable growth in the development of catalytic reactions capable of activating unreactive C-H bonds. These methods allow for the synthesis of complex molecules from easily available and cheaper precursors in a fewer number of steps. Naturally, the development of C-H activation methods for direct functionalization of heterocyclic molecules, invaluable building blocks for pharmaceutical and synthetic chemistry and material science, has received substantial attention as well. This critical review summarizes the progress made in this field until November 2006 (117 references).

Palladium-Catalyzed Annulation of Aryl Heterocycles with Strained Alkenes

[reaction: see text] An annulation reaction proceeding by the intermolecular addition of an arylpalladium(II) halide across a strained alkene, followed by an intramolecular C-H functionalization of a pendant heterocycle is described. A variety of polycyclic heterocycles have been prepared from readily accessible haloaryl heterocycles by annulation with a range of strained alkene partners.