Hydroaminoalkylation for Amine Functionalization of Vinyl-Terminated Polyethylene Enables Direct Access to Responsive Functional Materials.

While functionalized polyethylenes (PEs) exhibit valuable characteristics, the constraints of existing synthetic approaches limit the variety of readily incorporated functionality. New methods to generate functionalized PEs are required to afford new applications of this common material. We report 100 % atom economic tantalum-catalyzed hydroaminoalkylation of vinyl-terminated polyethylene (VTPE) as a method to produce amine-terminated PE.

Catalytic Installation of Primary Amines Onto Polyolefins for Oligomer Valorization.

Polymerization of primary amine-containing monomers is challenging because the amine inhibits polymerization catalyst activity. An alternative approach to access primary amine functionalized polymers is postpolymerization modification. To this end, the hydroaminoalkylation of vinyl-terminated polyolefins with N-(trimethylsilyl)benzylamine is used to prepare primary amine-terminated polyolefins, with the free primary amine substituent being revealed upon hydrolytic work up.

Understanding mechanism driven regioselectivity in zirconium-catalysed hydroaminoalkylation: homoallylic amines from conjugated dienes.

The unexpected 4,1-hydroaminoalkylation of dienes provides selective access to linear homoallylic amines by zirconium catalysis. This switch from the traditional branched preferred regioselectivity to selective linear product formation using this early transition metal can be attributed to π-allyl intermediates. The reactivity of these isolated intermediates on a sterically accessible and coordinatively flexible chelating bis(ureate) Zr(iv) complex confirmed reversible C-C bond formation in hydroaminoalkylation catalysis.

Amine-Functionalized Polybutadiene Synthesis by Tunable Postpolymerization Hydroaminoalkylation.

Early transition metal-catalyzed hydroaminoalkylation is a powerful single-step method to selectively add amines to polybutadienes, offering an efficient strategy to access amine-functionalized polyolefins. Aryl and alkyl secondary amines were used with a tantalum catalyst to functionalize both 28 wt% () and 70 wt% () 1,2-polybutadiene polymers. The degree of amination was controlled by modifying amine and catalyst loading in both small- and multigram-scale reactions.

Tantalum ureate complexes for photocatalytic hydroaminoalkylation.

Using a tantalum ureate pre-catalyst, photocatalytic hydroaminoalkylation of unactivated alkenes with unprotected amines at room temperature is demonstrated. The combination of Ta(CHSiMe)Cl and a ureate ligand with a saturated cyclic backbone resulted in this unique reactivity. Preliminary investigations of the reaction mechanism suggest that both the thermal and photocatalytic hydroaminoalkylation reactions begin with N-H bond activation and subsequent metallaaziridine formation.

One-Pot Sequential Hydroamination Protocol for N-Heterocycle Synthesis: One Method To Access Five Different Classes of Tri-Substituted Pyridines.

Tri-substituted pyridines are important scaffolds that can be found in a plethora of commercially available drugs. A one-pot general method for the selective synthesis of less explored/challenging patterns of tri-substituted pyridines is described. Hydroamination of alkynes with commercially available -triphenylsilylamine generates -silylenamines.

Vanadium pyridonates: dimerization, redox behaviour, and metal-ligand cooperativity.

The synthesis, structure, and reactivity of vanadium pyridonate complexes are described. Vanadium(III) pyridonate complexes were accessed through protonolysis and reduction of a tetrakis(amido)vanadium(IV) starting material. Bis(pyridonate) vanadium(IV) precursors could be isolated depending on the amount of proteoligand added.

The Catalytic Synthesis of -Aryl Indoles Featuring an Alternative Disconnection. Hydroaminoalkylation for a Telescoped Reaction Sequence.

A tricatalytic telescoped synthesis toward C3-methyl--aryl indoline and indole products is reported. An generated tantalum(V) ureate catalyst is used for the hydroaminoalkylation of -chlorostyrene with -methylaniline to first make a C─C bond. Subsequent nickel-catalyzed C-N coupling forms -aryl indolines, and if desired, subsequent oxidation to -aryl indoles can be achieved using catalytic [Cu(MeCN)]BF and -butylperoxy-2-ethylhexyl carbonate as the terminal oxidant.

-Silylamines in catalysis: synthesis and reactivity.

A summary of the catalytic synthesis and reactivity of -silylated amines is presented. Dehydrocoupling of amines with silanes, hydrosilylation of imines and dealkenylative coupling of amines with vinylsilanes are three ways to achieve their catalytic syntheses. The resultant -silylamines serve as substrates in a variety of reactions, including C-N and C-C bond forming reactions, and are preferred in transformations because of the facile Si-N hydrolytic cleavage to reveal free amine products upon reaction completion.

Hydroaminoalkylation for the Catalytic Addition of Amines to Alkenes or Alkynes: Diverse Mechanisms Enable Diverse Substrate Scope.

Hydroaminoalkylation is a powerful, atom-economic catalytic reaction for the reaction of amines with alkenes and alkynes. This C-H functionalization reaction allows for the atom-economic alkylation of amines using simple alkenes or alkynes as the alkylating agents. This transformation has significant potential for transformative approaches in the pharmaceutical, agrochemical, and fine chemical industries in the preparation of selectively substituted amines and -heterocycles and shows promise in materials science for the synthesis of functional and responsive aminated materials.

Commodity Polymers to Functional Aminated Materials: Single-Step and Atom-Economic Synthesis by Hydroaminoalkylation.

Hydroaminoalkylation (HAA) is demonstrated to be a promising postpolymerization route to catalytically prepare amine-functionalized atactic polypropylene. Using a recently reported tantalum catalyst supported by a ,-chelating cyclic ureate ligand, vinyl-terminated polypropylene (VTPP) is transformed into both aryl and alkyl secondary amine-terminated polyolefins. Early transition-metal-catalyzed hydroaminoalkylation avoids protection/deprotection protocols typically required for secondary amine synthesis.

Direct metal-carbon bonding in symmetric bis(C-H) agostic nickel(i) complexes.

Agostic interactions are examples of σ-type interactions, typically resulting from interactions between C-H σ-bonds with empty transition metal d orbitals. Such interactions often reflect the first step in transition metal-catalysed C-H activation processes and thus are of critical importance in understanding and controlling σ bond activation chemistries. Herein, we report on the unusual electronic structure of linear electron-rich d Ni(i) complexes with symmetric bis(C-H) agostic interactions.

Direct, Catalytic α-Alkylation of -Heterocycles by Hydroaminoalkylation: Substrate Effects for Regiodivergent Product Formation.

Saturated -heterocycles are prevalent in pharmaceutical and agrochemical industries, yet remain challenging to catalytically alkylate. Most strategies for C-H activation of these challenging substrates use protected amines or high loadings of precious metal catalysts. We report an early transition-metal system for the broad, robust, and direct alkylation of unprotected amine heterocycles with simple alkenes.

Using Catalysts To Make Catalysts: Titanium-Catalyzed Hydroamination To Access -Ligands for Assembling Catalysts in One Pot.

Using a diamido-bis(amidate) titanium precatalyst, the hydroamination of alkynylphosphines afforded phosphinoenamine products. After reduction, 2-aminophosphines are prepared in excellent yield and on gram scale. A broad variety of alkynylphosphines and primary amines with different electronic and steric features are tolerated in this sequential transformation, enabling the rapid assembly of a collection of ligands.

Zirconium Catalyzed Hydroaminoalkylation for the Synthesis of α-Arylated Amines and N-Heterocycles.

The zirconium catalyzed hydroaminoalkylation of alkenes with N-aryl- and sterically demanding N-alkyl-α-arylated secondary amines by using commercially available Zr(NMe ) is reported. N-phenyl- and N-isopropylbenzylamine are used as amine substrates to establish the alkene substrate scope. Exclusively linear products are obtained in the presence of bulky vinylsilanes.

Zirconium-Catalyzed Hydroaminoalkylation of Alkynes for the Synthesis of Allylic Amines.

A zirconium-catalyzed hydroaminoalkylation of alkynes to access -substituted allylic amines in an atom-economic fashion is reported. The reaction is compatible with -(trimethylsilyl)benzylamine and a variety of -benzylaniline substrates, with the latter giving the allylic amine as the sole organic product. Various internal alkynes with electron-withdrawing and electron-donating substituents were tolerated.

Titanium catalysis for the synthesis of fine chemicals - development and trends.

Titanium is the second most abundant transition metal and is already a key player in important industrial processes (e.g. polyethylene).

Cyclic Ureate Tantalum Catalyst for Preferential Hydroaminoalkylation with Aliphatic Amines: Mechanistic Insights into Substrate Controlled Reactivity.

The efficient and catalytic amination of unactivated alkenes with simple secondary alkyl amines is preferentially achieved. A sterically accessible, ,-chelated cyclic ureate tantalum catalyst was prepared and characterized by X-ray crystallography. This optimized catalyst can be used for the hydroaminoalkylation of 1-octene with a variety of aryl and alkyl amines, but notably enhanced catalytic activity can be realized with challenging -alkyl secondary amine substrates.

Vanadium Pyridonate Catalysts: Isolation of Intermediates in the Reductive Coupling of Alcohols.

The reductive coupling of alcohols using vanadium pyridonate catalysts is reported. This attractive approach for C(sp)-C(sp) bond formation uses an oxophilic, earth-abundant metal for a catalytic deoxygenation reaction. Several pyridonate complexes of vanadium were synthesized, giving insight into the coordination chemistry of this understudied class of compounds.

Zirconium Hydroaminoalkylation. An Alternative Disconnection for the Catalytic Synthesis of α-Arylated Primary Amines.

Primary amine products have been prepared using zirconium-catalyzed hydroaminoalkylation of alkenes with -silylated benzylamine substrates. Catalysis using commercially available Zr(NMe) affords an alternative disconnection to access α-arylated primary amines upon aqueous workup. Substrate-dependent regio- and diastereoselectivity of the reaction is observed.

Mono, bis, and tris(phosphoramidate) titanium complexes: synthesis, structure, and reactivity investigations.

A series of variously substituted phosphoramidate titanium complexes bearing dimethylamido ligands are reported. Aryl-substituted ligands impart crystallinity to the systems and allow for the elucidation of the molecular structures via X-ray crystallography. Higher-substituted complexes, including a tris(phosphoramidate)mono(dimethylamido) complex, were isolated and characterized in the solid state, as well as in solution using variable temperature 1H and 31P NMR spectroscopy.

N-Silylenamines as Reactive Intermediates: Hydroamination for the Modular Synthesis of Selectively Substituted Pyridines.

A modular and selective synthesis of mono-, di-, tri-, tetra-, and pentasubstituted pyridines is reported. Hydroamination of alkynes with N-silylamine using a bis(amidate)bis(amido)titanium(IV) precatalyst furnishes the regioselective formation of N-silylenamines. Addition of α,β-unsaturated carbonyls to the crude mixtures followed by oxidation affords 47 examples of pyridines in yields of up to 96%.