Catalytic Reactions Directed by a Structurally Well-Defined Aminomethyl Cyclopalladated Complex

Enantioselective Ring-Closing Aminomethylamination of Allylic Aminodienes with Aminals Triggered by C-N Bond Metathesis

A conceptually novel strategy utilizing a cyclopalladated complex as an electrophile to activate the C-N bond for the C-N bond metathesis between allylamines and aminals is developed, which enables an efficient ring-closing aminomethylamination of allylic aminodienes and aminals. The reaction proceeds under mild reaction conditions and displays a remarkable scope. Utilizing a modified Trost-type diphosphine as the ligand, this method enables the efficient synthesis of 5-10-membered aminoallylated chiral N-heterocycles in good yields with high enantiomeric excess values.

Intramolecular Carboamination of Aminodienes to N-Heterocycles via C-N Bond Activation

The catalytic transformation of ubiquitous but inert C-N bonds is highly appealing in synthetic chemistry, but the efficient cleaving inert C-N bond and simultaneous incorporation of both the cleaved C-moiety and N-moiety into the desired products has been a long-standing formidable challenge so far. Here, we developed a radical-addition triggered cyclization and C-N bond cleavage process enabled by the unique I2 /Ni or benzyl halide/Ni-catalytic system, allowing the formal insertion of diene into the inert C-N bond. This reaction features high atom economy and enables an expedient annulative carboamination of aminodienes to diverse pyrrolidines, piperidines, and tetrahydroisoquinolines. Mechanistic studies have revealed that the reaction is initiated via the generation of a benzyl radical and the formation of quaternary ammonium salt is key for the C-N bond cleavage.

Palladium-Catalyzed Aminoalkylative Cyclization Enables Modular Synthesis of Exocyclic 1,3-Dienes

A novel and efficient palladium-catalyzed regioselective and stereodivergent ring-closing reaction of aminoenynes with aldehydes and boronic acids or hydrosilane is developed. This three-component reaction allows for the modular synthesis of a series of exocyclic 1,3-dienes bearing 5- to 8-membered saturated N-heterocycles. The reactions utilize a simple Pd-catalyst and work with broad range of aminoenynes, aldehydes and organometallic reagents under mild reaction conditions. The products represent useful intermediates for chemical synthesis due to the versatility of the conjugated diene. Preliminary mechanistic details of the method are also revealed.

Photocatalyzed Aminomethylation of Alkyl Halides Enabled by Sterically Hindered N-Substituents

The catalytic C(sp3 )-C(sp3 ) coupling of alkyl halides and tertiary amines offers a promising tool for the rapid decoration of amine skeletons. However, this approach has not been well established, partially due to the challenges in precisely distinguishing and controlling the reactivity of amine-coupling partners and their product homologues. Herein, we developed a metal-free photocatalytic system for the aminomethylation of alkyl halides through radical-involved C(sp3 )-C(sp3 ) bond formation, allowing for the synthesis of sterically congested tertiary amines that are of interest in organic synthesis but not easily prepared by other methods. Mechanistic studies disclosed that sterically hindered N-substituents are key to activate the amine coupling partners by tuning their redox potentials to drive the reaction forward.

Palladium-Catalyzed Ring-Closing Aminoalkylative Amination of Unactivated Aminoenynes

An efficient strategy for preventing the β-hydride elimination of alkylpalladium species by ligation of the palladium with adjacent amino-group was developed, which enabled a novel palladium-catalyzed ring-closing aminoalkylative amination of unactivated aminoenynes. The reaction is amenable to aminals, as well as aliphatic aldehydes with secondary amines, which provides straightforward access to structurally diverse exocyclic allenic amines bearing 5 to 12-membered N-heterocycles. With chiral phosphoramidite-ligated palladium complex as the catalyst, an enantioselective variant was achieved with up to 93 % ee. Simultaneously, synthetic transformations of the chiral products were also conducted to afford structurally unique spirodiamines including one pharmaceutically active molecule via axial-to-central chirality transfer.

Silver-catalyzed chemodivergent assembly of aminomethylated isochromenes and naphthols

A silver-catalyzed chemodivergent cyclization of alkyne-tethered aldehydes with aminals to aminomethylated 1H-isochromenes and naphthols is described by tuning the reaction conditions. The reaction exhibits broad substrate generality and functional group compatibility. Mechanistic studies have disclosed that the aminomethylated naphthols are generated from the resulting N,O-aminal containing isochromenes via a silver-catalyzed unusual rearrangement process.

Highly Regioselective and Ligand-Controlled Diastereodivergent Aminomethylative Annulation of Dienyl Alcohols Enabled by Hydrogen-Bonding Assisting Effect

A ligand-controlled palladium-catalyzed highly regioselective and diastereodivergent aminomethylative annulation of dienyl alcohols with aminals has been established, which allows for producing either cis- or trans-disubstituted isochromans in good yields with...

Palladium-Catalyzed Aminomethylative Oppolzer-Type Cyclization of Enynes: Access to Aminomethylated Benzofulvenes

A novel palladium-catalyzed Oppolzer-type cyclization reaction aided by the aminomethyl cyclopalladated complex has been developed, which provides rapid access to functionalized benzofulvenes with excellent stereoselectivity. The corresponding products can undergo Diels-Alder reaction with maleimides, providing a series of complex polycyclic compounds with excellent regio- and stereoselectivities.