Benzyl Palladium Intermediates: Unique and Versatile Reactive Intermediates for Aromatic Functionalization

Abstract

Aromatic functionalizations are of current interest and importance in organic chemistry, recent transition‐metal catalyzed reactions can transform inert C−H bond into C−X (X=C, O, N, etc.) bonds, greatly enriching aromatic chemistry and related fields. Some well‐known palladium‐containing intermediates such as palladacycles and allylpalladium intermediates play an important role in organic conversions. Similar with allyl group, benzyl group also possesses the capability of stabilizing palladium through η3‐binding. In the process of the formation of benzyl palladium intermediate, there is a transition state of dearomatization. Therefore, it is a challenging and meaningful research topic to seize these aromatic destruction intermediates, realize selective functionalization reaction on aromatic ring via them, and inhibit the formation of traditional benzylated products. Herein, we summarized the recent efforts on expanding the synthetic utility, as well as exploring the mechanism in aromatic functionalization via reactive benzyl palladium intermediates. We envision that the transformation via benzyl palladium intermediates will help promote the development in the field of palladium–catalyzed aromatic regioselective functionalization.

Palladium‐Catalyzed Three‐Component Coupling Reaction via Benzylpalladium Intermediate

“…Very recently, we published a review article on the aromatic functionalization via reactive benzylpalladium intermediates. [9] Herein, we will mainly summarize our studies on palladiumcatalyzed three-component coupling reactions via benzylpalladium intermediates, as well as the related studies reported by other groups.…”

Exploring benzylic gem-C(sp3)–boron–silicon and boron–tin centers as a synthetic platform

“…benzyl chlorides), and not nucleophiles, as is the case in our system. 24 While a number of mechanistic manifolds can be envisioned leading to such side-products, one possibility is illustrated in the beige inset in Scheme 10C . Assuming a canonical oxidative addition/transmetallation path, species 33inv could arise from the isomerization of the Pd( ii )-benzyl fragment to one of its para -palladated forms prior to reductive elimination.…”

Convergent Azaspirocyclization of Bromoarenes with N-Tosylhydrazones by a Palladium Catalyst

“…This methodology is advantageous because of the high availability of haloarenes as a starting material and the convergency of the reaction. The key finding in these reactions was the generation of a benzyl–Pd intermediate , by the action of haloarenes and diazo compounds such as TMS diazomethane and N -tosylhydrazones . We envisaged that this type of reaction can be applied to the synthesis of 1-azaspirocycles using bromoarenes bearing an aminoalkyl chain through an intramolecular C–N bond formation on a benzyl–Pd species.…”