Nickel Catalyst Delivers Chiral Allylic Amines from Simple Enamines and Alkynes

Chemists at the Southern University of Science and Technology in Shenzhen have unveiled a nickel-catalysed reaction that builds one of the most sought-after motifs in drug discovery — the chiral allylic amine — from two simple and abundant feedstocks: enamines and alkynes. Writing in Nature Synthesis, the team led by Wei Shu describes a process that stitches these fragments together in a single catalytic operation while controlling, with remarkable precision, both where the new bond forms and which mirror-image version of the product is made. The work, published on 13 October 2026, addresses a long-standing gap in the synthetic toolbox, because enantioenriched aliphatic allylic amines have historically been difficult to access directly from readily available starting materials.

Allylic amines are everywhere in biologically active chemistry. They appear as substructures in natural products, in pharmaceutical candidates, and in the alkene isosteres used to mimic peptide bonds in drug design. Their appeal as building blocks goes beyond mere prevalence: because an allylic amine carries an alkene, an amine and a stereocentre in close proximity, each of these reactive sites can be manipulated independently, a property chemists describe as orthogonal reactivity. That versatility makes them ideal launch pads for constructing value-added targets, from aza-heterocycles to modified alkaloids. Yet most existing routes to their chiral versions rely on pre-activated substrates such as allylic acetates, on stoichiometric chiral auxiliaries, or on multi-step sequences that erode efficiency.

The conceptual heart of the new method is homologation — the controlled lengthening of a molecular skeleton. Homologation strategies have enjoyed a renaissance in recent years, with one-carbon extensions of carboxylic acids, alkenes and organoboron compounds all demonstrating how growing a carbon chain catalytically can shortcut traditional synthesis. The Shu group applies this logic to enamines, nitrogen-substituted alkenes that are cheap, electron-rich and easily prepared from carbonyl compounds. By coupling an enamine with an alkyne under nickel catalysis, the reaction effectively inserts the alkyne-derived fragment onto the enamine framework, converting it into an allylic amine that is one hydrocarbon unit longer and, crucially, chiral.

Technically, the transformation is an enantioselective C(sp2)–C(sp3) cross-coupling, a class of reaction that has become one of the most competitive arenas in modern catalysis. Nickel is the metal of choice for several reasons: it is earth-abundant compared with palladium, it readily shuttles between oxidation states, and it tolerates the kind of unactivated alkyl intermediates that would decompose on more precious metals. In the reported system, a chiral ligand environment around nickel governs both the regiochemistry — which carbon of the alkyne receives which partner — and the enantioselectivity, delivering products in good yields with excellent enantiomeric excess across a broad substrate scope.

Perhaps the most striking feature is the chemoselectivity that makes the reaction possible at all. Mechanistic investigations by the team revealed that the catalytic cycle hinges on a selective hydrometallation step in which nickel hydride adds preferentially to the electron-rich alkene of the enamine rather than to the more electrophilic linear alkyne present in the same flask. That preference runs counter to what simple electronic intuition might predict, since electrophilic alkynes typically react faster with metal hydrides. By favouring the less obvious partner, the catalyst generates an alkyl-nickel species that then engages the alkyne in the bond-forming event, setting up the stereochemistry-defining step of the cycle.

The scope of the reaction, documented across the paper’s substrate tables and crystallographically confirmed structures, spans a wide range of alkynes and enamines. Six crystal structures deposited with the Cambridge Crystallographic Data Centre underpin the structural assignments, giving the community unambiguous three-dimensional confirmation of the products’ configurations. The breadth matters practically: medicinal chemists rarely work with a single substrate class, and a method that accommodates varied substitution patterns on both coupling partners is far more likely to be adopted in late-stage or discovery settings than one restricted to narrow examples.

The synthetic utility is demonstrated most convincingly in the applications section, where the authors show that the reaction provides a convenient route to a range of bioactive molecules and key intermediates. Among the targets accessible through the chemistry are motifs related to monoamine oxidase inhibitors and CCR3 antagonist scaffolds, compounds whose chiral allylic amine cores have traditionally demanded lengthy asymmetric sequences. Because the products retain multiple reactive handles — the alkene, the amine and any additional functionality inherited from the alkyne — they can be elaborated further, meaning the reaction functions not just as an endpoint but as a strategic gateway within a longer synthesis.

The work also fits into a broader pattern in the Shu group’s research programme, which has focused on nickel-catalysed asymmetric cross-hydrodimerization and hydroalkylation reactions of unsaturated partners. Earlier contributions from the same laboratory include enantioselective alkyl–alkyl couplings of alkenes and cobalt-catalysed cross-hydrodimerizations of dienes with alkynes. The new enamine homologation extends this reactivity-mode thinking to nitrogen-containing substrates, showing how the same mechanistic family — hydrometallation followed by controlled C–C bond formation — can be redirected toward different product classes by changing the coupling partners and ligand design.

For the pharmaceutical industry, the significance is twofold. First, the method converts commodity starting materials into high-value chiral intermediates in a single step, which translates directly into fewer operations, less waste and lower cost in process chemistry. Second, because the products are enantioenriched aliphatic allylic amines rather than aryl-substituted analogues, the chemistry reaches a subclass that asymmetric hydrogenation and classical imine alkenylation methods have served poorly. Homologation itself is increasingly recognised in medicinal chemistry as a powerful strategy for exploring the property space around a lead compound, and a catalytic, enantioselective homologation of amines gives drug hunters a new dial to turn when optimising potency, selectivity and metabolic stability.

The study, supported by the National Natural Science Foundation of China and regional funding bodies in Guangdong and Sichuan, was peer reviewed at Nature Synthesis with crystallographic and mechanistic evidence available in the supplementary materials. As nickel catalysis continues to displace precious-metal chemistry across the synthesis landscape, this enamine-to-allylic-amine homologation stands out as a template for how careful mechanistic insight — here, the counterintuitive selectivity of hydrometallation — can unlock transformations that were previously out of reach, and it is likely to inspire a wave of follow-up work aimed at extending homologation logic to other functional groups and feedstock combinations.

Subject of Research: Nickel-catalysed regio- and enantioselective homologation of enamines with alkynes to synthesize chiral allylic amines

Article Title: Synthesis of chiral allylic amines through regio- and enantioselective homologation of enamines using Ni catalysis

Article References: Synthesis of chiral allylic amines through regio- and enantioselective homologation of enamines using Ni catalysis. (n.d.). https://doi.org/10.1038/s44160-026-01172-8

Image Credits: AI Generated

DOI: 10.1038/s44160-026-01172-8

Keywords: nickel catalysis, chiral allylic amines, enamines, alkynes, homologation, asymmetric catalysis, cross-coupling, hydrometallation, reaction mechanism, drug discovery, synthetic methodology, Nature Synthesis