Palladium-Catalyzed sp2–sp3 Coupling of Chloromethylarenes with Allyltrimethoxysilane: Synthesis of Allyl Arenes

Palladium-Catalyzed para-Selective Allylation of 1-(Cyanomethyl)arenes with Allyl Acetates

The Pd/PMe₃-catalyzed allylation of 1-(cyanomethyl)naphthalenes with allyl acetates proved to be para- rather than α-regioselective. This reaction is thought to proceed through ligand attack of the para-carbon in the arenes, electronically enriched by a cyano-stabilized α-carbanion, to the (π-allyl)palladium and a 1,5-hydrogen shift of the para-hydrogen from the dearomatized intermediate.

Electrophilic Trapping of Semibenzenes

In this work, we demonstrate how allylative dearomatization of benzyl chlorides can provide direct access to a variety of semibenzenes. These scaffolds behave as highly reactive nucleophiles in the presence of carbocations. In addition, semibenzenes are susceptible to intramolecular rearrangements rendering a broad scope of functionalized arenes. An analysis of this new reactivity is reported, as well as the rationale behind the observed intramolecular reorganizations.

Palladium-Catalyzed Para-C-H Bond Amination of 2-Aryl Chloromethylbenzenes

Palladium-catalyzed para-C-H bond amination of 2-aryl chloromethylbenzenes is described for the first time. The reactions of 2-aryl chloromethylbenzenes with cyclic amines proceeded smoothly in the presence of Pd(acac)₂, tri(2-furyl)phosphine, and NaH in tetrahydrofuran at 40 °C to provide para-C-H bond aminated products in satisfactory to high yields with acceptable regioselectivity in most cases. The electronic property of the substituents linked to the benzene rings did not significantly influence the reactivity of the 2-aryl chloromethylbenzene substrates and the reaction regioselectivity.

Spirocarbocycle Synthesis from Chloromethylarenes via Transition-Metal-Catalyzed Allylative Dearomatization and Ring Closure Metathesis

A strategy for the synthesis of spirocarbocycles by using chloromethyl arenes as starting materials is described in this paper. The palladium-catalyzed allylative dearomatization and the subsequent ruthenium-catalyzed ring closure metathesis proceeded smoothly under mild conditions to produce the corresponding spirocarbocycle products with moderate to high yields. Benzene-ring-, naphthalene-ring-, and anthracene-ring-containing substrates can be easily transformed into spirocarbocycles by using the proposed method.

Pd-catalyzed allylative dearomatisation using Grignard reagents

Pd-catalyzed allylative dearomatisation of naphthyl halides is shown to be feasible by employing Grignard reagents. The high reactivity of the nucleophile allows for fast reactions and low catalyst loading, while a plethora of successfully substituted compounds illustrate the broad scope. Five membered heteroaromatic compounds are also demonstrated to be reactive under similar conditions.

Highly Regioselective Aromatic C-H Allylation of N-(Arylmethyl)sulfonimides with Allyl Grignard Reagents Involving Benzylic C-N Cleavage

A new pair of reaction partners has been established for the aromatic C-H functionalization of benzyl electrophiles with nucleophiles via palladium-catalyzed benzylic C-N cleavage. A range of N-(1-naphthylmethyl)sulfonimides, N-(2-thienylmethyl)sulfonimides, and N-(2-furanylmethyl)sulfonimides smoothly underwent palladium-catalyzed aromatic C-H allylation with allyl Grignard reagents at room temperature, delivering structurally diverse substituted 1-allylnaphthalenes and 2-allylheteroarenes in moderate to excellent yields with extremely high regioselectivities. Replacing the N-(arylmethyl)sulfonimide with an (arylmethyl)ammonium salt, an arylmethyl chloride, or an arylmethyl phosphate as the benzyl electrophile leads to a dramatic erosion of the regioselectivity.

Recent advances in multi-component reactions and their mechanistic insights: a triennium review

This review summarizes the recent developments in MCRs, incorporating different strategies along with their mechanistic aspects.

Palladium-catalyzed dearomative 1,4-difunctionalization of naphthalenes

A highly diastereoselective dearomatization of naphthalenes via a Pd-catalyzed 1,4-difunctionalization reaction is described. In the presence of a commercially available palladium precursor and ligand, intramolecular dearomative Heck-type insertion provides π-allylpalladium intermediates which are readily captured by a series of nucleophiles in excellent yields (up to 99%). This reaction features mild conditions, broad substrate scope, and useful transformations of the products.

Dearomative Allylation of Naphthyl Cyanohydrins by Palladium Catalysis: Catalyst-Enhanced Site Selectivity

A dearomative allylation of naphthyl cyanohydrins with allyl borates and allyl stannanes under palladium catalysis was developed. At the initial stage of this study, the dearomative reaction (C4 substitution of the aromatics) was competing with benzyl substitution. To circumvent this issue, the use of palladium and meta-disubstituted triarylphosphine as the catalyst in a 1:1 ratio was found to enhance the site selectivity, furnishing the desired dearomatized products. Further derivatizations of products were also successful.

Palladium-Catalyzed Hiyama Cross-Couplings of Arylsilanes with 3-Iodoazetidine: Synthesis of 3-Arylazetidines

The first palladium-catalyzed Hiyama cross-coupling reactions of arylsilanes with 3-iodoazetidine were described. The protocol provides a convenient access to a variety of useful 3-arylazetidines which are of great interest in pharmaceutical laboratories in moderate to good yields (30%-88%). In addition, this strategy has the advantage of easy operation and mild reaction conditions.