A three-stage synthesis reported by Quang H. Luu and Junqi Li converts cyclic diarylmethanes and related diarylketones into cyclic diarylethers. The route first oxidizes a methylene group to a ketone, inserts oxygen through Baeyer–Villiger oxidation to make a lactone, and then uses nickel-catalyzed decarbonylation to remove the targeted carbon as carbon monoxide while forming the aryl–oxygen bond. In the authors’ 2022 study, the key lactone step covered 16 examples involving six- to eight-membered rings, with isolated yields from 32% to 99%.
What the atom-swapping reaction actually does
Cyclic diarylmethanes contain a carbon atom within a ring that connects two aryl groups. In a cyclic diarylether, oxygen occupies the analogous position. Luu and Li’s method changes that framework, but not by replacing carbon with oxygen in a single elementary reaction. It is a programmed sequence in which oxidation and rearrangement create an oxygen-bearing intermediate, followed by nickel-mediated carbon removal.
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The primary report, published in Chemical Science (2022, volume 13, issue 4, pages 1095–1100), describes the sequence as a C-to-O atom swap enabled by nickel-catalyzed decarbonylation of lactones. The Royal Society of Chemistry record lists first publication on 6 January 2022; PubMed lists the issue date as 26 January 2022. Those are two dates for the same article, not separate discoveries.
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The three-stage sequence
| Stage | Starting framework | Chemical operation | Intermediate or product |
|---|---|---|---|
| 1. Methylene oxidation | Cyclic diarylmethane | Oxidize the methylene position embedded in the ring | Cyclic diarylketone |
| 2. Oxygen insertion | Cyclic diarylketone | Baeyer–Villiger oxidation inserts an oxygen next to the carbonyl | Cyclic lactone |
| 3. Carbon removal and ether formation | Cyclic lactone | Nickel-catalyzed decarbonylation extrudes carbon monoxide | Cyclic diarylether |
This order matters. The carbon that ultimately disappears is first converted into a carbonyl-containing arrangement that can participate in Baeyer–Villiger chemistry. Oxygen insertion then produces a lactone, a ring containing an ester group. Nickel catalysis enables the lactone to lose carbon monoxide and close the sequence as a diaryl ether.
Stage 1: oxidizing a ring methylene to a ketone
The first operation changes the saturated methylene group of a cyclic diarylmethane into a ketone. That oxidation increases the carbon’s reactivity and creates the carbonyl required for the next rearrangement. In structural terms, the method does not attempt to attack an unactivated C–C bond directly. It first converts the local environment into one that can undergo a controlled oxygen-transfer reaction.
The article’s abstract-level record identifies this oxidation as the opening step but does not establish one universal oxidant or a single set of conditions for every substrate. Consequently, the reported transformation should not be read as proof that any diarylmethane will oxidize cleanly. Substrate electronics, ring strain, benzylic substitution and competing oxidation pathways can affect whether a suitable diarylketone is obtained.
Stage 2: Baeyer–Villiger oxidation builds the lactone
Baeyer–Villiger oxidation converts a ketone into an ester by inserting an oxygen adjacent to the carbonyl. When the ketone is part of a ring, that insertion expands the ring and gives a lactone. The operation is strategically useful here because it places an oxygen atom into the framework before the carbon-removal step.
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Which side of an unsymmetrical ketone migrates during Baeyer–Villiger oxidation can determine the substitution pattern of the resulting lactone. That regiochemical issue is one reason the overall method is a sequence rather than a universal one-pot exchange: the ketone must rearrange in a way that leaves the desired aryl groups and ring topology available for nickel-catalyzed decarbonylation.
The lactone is therefore more than a protecting group or temporary functional handle. It is the engineered intermediate that contains both the oxygen destined for the diaryl ether and the carbonyl unit that can be removed as carbon monoxide.
Stage 3: nickel-catalyzed decarbonylation completes the swap
In the final stage, nickel catalysis acts on the lactone framework. Decarbonylation removes the carbonyl carbon and oxygen as carbon monoxide, while the remaining aryl fragments form a C–O bond to give the cyclic diarylether. This is the step that makes the overall sequence look like an atom swap, although the oxygen was installed earlier and the carbon is removed only after lactone formation.
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Luu and Li report that their development work included mechanistic studies with stoichiometric nickel(II) complexes. They also optimized a ligand that supports the difficult reductive-elimination event needed to form a C(sp²)–O(aryl) bond. Aryl–oxygen reductive elimination can be challenging because the catalyst must bring the aryl groups and oxygen into the correct electronic and geometric relationship without promoting decomposition. The ligand design was consequently central to making lactone decarbonylation productive.
Because carbon monoxide is generated, this is a reaction for a properly equipped chemistry laboratory, with appropriate containment, monitoring and waste procedures. The paper demonstrates a synthetic method; it does not describe a consumer process or a scalable commercial product.
What was demonstrated experimentally
The reported nickel-catalyzed lactone decarbonylation was applied to 16 examples spanning six-, seven- and eight-membered lactones. Across those examples, the authors reported yields ranging from 32% to 99%.
| Reported measure | What it means | Qualification |
|---|---|---|
| 16 examples | Number of lactone substrates tested in the reported scope | Attributed to Luu and Li, 2022 |
| Six- to eight-membered lactones | Ring-size range represented in that scope | Does not establish performance outside this range |
| 32%–99% yields | Isolated yields reported across the examples | Individual substrates differed; the range is not an average or guaranteed outcome |
A yield range this broad is a scope result, not a promise that a new substrate will fall near the upper end. It shows that the catalytic step can tolerate more than one ring size and substitution pattern, while also revealing that substrate structure strongly affects efficiency. The available summary does not provide a substrate-by-substrate table, so it cannot support claims about which particular substituents produced 32% or 99%.
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Why the transformation is useful to synthetic chemists
Diarylethers are common motifs in medicinal chemistry, natural products and materials research. Conventional routes often build the C–O bond from prefunctionalized aryl partners, such as aryl halides and phenoxide-like nucleophiles. Luu and Li’s approach starts from a different structural inventory: an existing cyclic diarylmethane can, in principle, be edited into the oxygen-containing analogue without dismantling the entire ring system.
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That editing concept can be valuable when a carbon-based scaffold is already available from an earlier synthesis or occurs in a complex molecule. Instead of designing a completely new coupling sequence, a chemist can consider whether oxidation, Baeyer–Villiger rearrangement and decarbonylation are compatible with the scaffold. The benefit is greatest when the carbon framework and aryl substitution pattern are otherwise desirable and only the heteroatom identity needs to change.
The method also illustrates a broader retrosynthetic strategy: use a functional group interconversion to create a bond-breaking event that would be difficult to perform directly. Direct cleavage of a strong ring C–C bond and simultaneous installation of oxygen would be a demanding transformation. Converting the ring into a lactone makes carbon loss chemically accessible through decarbonylation.
Applications shown in complex molecules
The authors applied the overall C-to-O sequence to a natural product and to a pharmaceutical precursor. These demonstrations support the feasibility of carrying the strategy into more elaborate molecular settings than simple model substrates.
They do not establish a medicine, a clinical effect or a manufacturing process. A pharmaceutical precursor is an intermediate used in synthesis, not an approved drug. Likewise, transforming a natural product shows that the sequence can be attempted on a complex framework; it does not prove biological activity, improved potency or safety.
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Chemistry World’s 15 February 2022 report described the approach as potentially useful for pharmaceutical intermediates and noted compounds containing a dibenzoazepine motif. “Potentially useful” is the appropriate level of certainty: the study provides synthetic evidence, while development, scale-up and regulatory performance would require separate work. Chemistry World’s report provides that contemporaneous context.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How to evaluate whether a substrate is a good candidate
A reader trying to apply the concept should treat it as a compatibility problem across three operations rather than as a single reaction label.
Check the starting ring and benzylic position
- The cyclic diarylmethane must contain a methylene position that can be oxidized to the required ketone.
- Substitution at or near that position can affect oxidation rate, selectivity and the stability of the ketone.
- Both aryl groups must survive the oxidation conditions well enough to reach the lactone stage.
Check Baeyer–Villiger regiochemistry
- For an unsymmetrical ketone, migration preference determines which lactone is formed.
- Ring expansion must produce a lactone geometry that the nickel catalyst can engage.
- Functional groups that react with the oxidant or rearrangement conditions can lower the effective yield before catalysis is attempted.
Check the decarbonylation step
- The lactone must be within the demonstrated structural class or be justified as a new substrate for experimentation.
- The aryl–oxygen bond-forming reductive elimination is sensitive to catalyst and ligand design.
- Carbon monoxide evolution requires laboratory engineering controls and an experimentally validated work-up.
For a multistep synthesis, the overall yield is the product of the isolated yields at each stage. Even when the decarbonylation gives a high yield, losses during oxidation and lactone formation can make the sequence’s total yield substantially lower. Conversely, a moderate final-step yield may still be useful if the earlier intermediates are made efficiently or are valuable enough to justify the route.
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1Repair Windows errors before they cause bigger problems2Scan for outdated or missing drivers - takes under a minute3Clear out junk files and repair common Windows errorsWhat the phrase “atom swap” should and should not imply
The phrase is a concise description of the net structural change: one carbon in the ring is replaced by oxygen in the final product. It should not be interpreted as a one-step exchange in which a catalyst simply removes a carbon atom and inserts oxygen at the same instant.
Mechanistically, oxygen insertion and carbon removal are separated. Oxidation creates a ketone; Baeyer–Villiger chemistry turns that ketone into a lactone; nickel-catalyzed decarbonylation then expels carbon monoxide and forms the diaryl ether. Keeping those operations distinct helps explain both the power and the limitations of the method: each stage has its own substrate requirements, selectivity issues and yield loss.
Publication record and evidence boundaries
The study was authored by Quang H. Luu and Junqi Li of the Department of Chemistry at Iowa State University. Its primary evidence is a synthetic scope of lactone decarbonylation, mechanistic work on nickel complexes and demonstrations on a natural product and a pharmaceutical precursor.
Those data support three defensible conclusions:
- The sequence can convert selected cyclic diarylmethanes or diarylketones into cyclic diarylethers through a lactone intermediate.
- Nickel catalysis can accomplish the decarbonylative, aryl–oxygen bond-forming step for the reported six- to eight-membered lactones.
- The approach is a proof of synthetic feasibility with reported yields of 32% to 99% across 16 examples.
The evidence does not establish universal substrate compatibility, a commercial manufacturing process, clinical utility or a marketed therapeutic. Those questions require experiments beyond the 2022 publication.
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