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Quang H. Luu and Junqi Li reported a three-stage synthesis that changes a carbon atom in a cyclic diarylmethane or diarylketone framework into oxygen. The sequence first oxidizes a methylene group to a ketone, uses Baeyer–Villiger oxidation to create a lactone, and then applies nickel-catalyzed decarbonylation to remove carbon monoxide while forming the cyclic diarylether. In their 2022 study, the lactone step was demonstrated on 16 substrates containing six- to eight-membered rings, giving reported yields from 32% to 99%.
What the C-to-O atom swap actually changes
A cyclic diarylmethane contains two aryl groups connected through a ring that includes a carbon atom. The Luu–Li strategy replaces that framework carbon with an oxygen atom, producing a cyclic diarylether. The product is not made by a single reaction in which carbon is directly exchanged for oxygen. Instead, the sequence temporarily converts the target carbon into a carbonyl-containing intermediate, inserts oxygen to make a lactone, and finally removes the carbonyl carbon as carbon monoxide.
This distinction matters when evaluating the method. It is best understood as a planned sequence of oxidation, oxygen insertion and carbon extrusion. The sequence preserves much of the original ring architecture while changing the heteroatom pattern that controls shape, polarity and reactivity.
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Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →Outbyte Driver Updater FREEFix the driver behind crashes, sound loss and screen glitchesFind Drivers →The primary report is Chemical Science 2022, volume 13, issue 4, pages 1095–1100. The Royal Society of Chemistry record lists first publication on 6 January 2022, while the PubMed record gives the issue date as 26 January 2022. The article and abstract are available from the Royal Society of Chemistry and PubMed.
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How the three-stage sequence works
| Stage | Structural change | Purpose in the overall swap |
|---|---|---|
| 1. Methylene oxidation | The selected methylene position in the cyclic diarylmethane is converted into a ketone. | Creates the carbonyl handle required for the next rearrangement. |
| 2. Baeyer–Villiger oxidation | Oxygen is inserted next to the ketone, converting the cyclic ketone into a lactone. | Builds a C–O bond and places a removable carbonyl carbon in the ring. |
| 3. Nickel-catalyzed decarbonylation | The lactone loses carbon monoxide; the remaining aryl fragments close through oxygen. | Extrudes the targeted carbon and delivers the cyclic diarylether. |
1. Oxidize the methylene to a ketone
The starting cyclic diarylmethane has a methylene group at the position that will ultimately disappear. Oxidizing that CH2 unit to a ketone changes the local bonding without yet removing the carbon. The ketone is a functional-group relay: it is easier to rearrange in a controlled way than the original methylene.
For a synthetic chemist, this first operation defines which carbon is being exchanged. Regioselectivity and compatibility with the aromatic rings are therefore important planning questions. The paper presents the oxidation as part of an integrated sequence rather than as a universal procedure for every diarylmethane scaffold.
2. Insert oxygen with a Baeyer–Villiger oxidation
Baeyer–Villiger oxidation rearranges a ketone after adding an oxygen atom adjacent to the carbonyl. In a cyclic ketone, that rearrangement expands the ring by one atom and produces a lactone, a cyclic ester. The new ester oxygen is the atom that will remain in the final diarylether.
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At this point, the molecule contains both the desired oxygen and a carbonyl carbon that can be removed. That design is the conceptual heart of the method: oxygen installation and carbon deletion are deliberately separated so that each can be optimized with a reaction class suited to it.
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Which side of an unsymmetrical ketone migrates during Baeyer–Villiger oxidation can affect the lactone structure. Consequently, substrate electronics, sterics and ring substitution may influence whether a particular diarylmethane gives the intended lactone. The reported study establishes the sequence on its demonstrated examples; it does not claim that every possible substrate will rearrange identically.
3. Remove carbon monoxide and form the ether
The final operation is nickel-catalyzed decarbonylation of the lactone. Nickel engages the lactone-derived framework, enables loss of carbon monoxide and promotes reductive elimination to create the aryl–oxygen bond. The product is a cyclic diarylether in which the carbon that occupied the original diarylmethane position is gone.
The authors describe mechanistic work with stoichiometric nickel(II) complexes and optimization of a ligand that supports the difficult C(sp2)–O(aryl) reductive-elimination event. That ligand-development effort is significant because aryl–oxygen bond formation from a nickel intermediate can compete with unproductive pathways. The paper therefore combines a synthetic sequence with mechanistic evidence aimed at explaining why the decarbonylation step works.
What was demonstrated experimentally
Luu and Li applied the nickel-catalyzed lactone decarbonylation to 16 examples involving six-, seven- and eight-membered lactones. Reported isolated yields span 32% to 99% across that set. Those figures describe the reported examples, not a guaranteed range for all cyclic lactones or all diarylether targets. Substrate identity, substitution and the preceding oxidation steps can change the outcome.
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| Reported dimension | What the 2022 paper establishes | How to interpret it |
|---|---|---|
| Number of lactone examples | 16 | A focused demonstration of scope, not an exhaustive library. |
| Ring sizes | Six- to eight-membered lactones | Shows the decarbonylation can operate across several medium-ring sizes. |
| Reported yields | 32%–99% | Yield varies substantially by substrate; the interval is not a prediction for a new molecule. |
| End-use demonstrations | One natural product and one pharmaceutical precursor | Evidence that the sequence can be integrated into more complex synthesis, not evidence of a medicine or clinical activity. |
The full article provides the substrate structures and individual results in its experimental scope. Because the abstract-level record does not establish a universal ranking of substituents or ring sizes, it would be misleading to infer that larger rings, electron-rich rings or any other class always gives the highest yield.
Why the decarbonylation step is the enabling chemistry
Oxidizing a methylene to a ketone and converting a ketone to a lactone are familiar transformations in organic synthesis. The unusual operation is the last one: using a transition-metal catalyst to remove the lactone carbonyl carbon as carbon monoxide while retaining the oxygen in an aryl–oxygen linkage.
Decarbonylation changes the molecular formula and connectivity at the same time. Carbon monoxide is a small, stable leaving product, so its extrusion can provide a strong thermodynamic and mechanistic driving force. However, the catalyst must guide the intermediate toward C(sp2)–O reductive elimination rather than cleaving the aryl–oxygen bond or undergoing other decomposition. The nickel/ligand system was developed to address that selectivity problem.
Thinking in terms of atom accounting helps prevent a common misunderstanding. The oxygen in the product comes from the oxygen-insertion stage; the carbon removed in the final stage leaves as carbon monoxide. No single elementary event performs a literal carbon-for-oxygen substitution.
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How to assess a new substrate before attempting the sequence
The publication demonstrates feasibility, but adapting the chemistry to a new molecule still requires route planning. A practical assessment should ask:
- Can the target carbon be oxidized selectively? The methylene to be exchanged must become the ketone used by the Baeyer–Villiger step, without unacceptable oxidation elsewhere.
- Which lactone regioisomer will form? In an unsymmetrical ketone, migration preference can determine where oxygen enters and whether the ring connectivity matches the desired diarylether.
- Is the ring size within the demonstrated window? Six- to eight-membered lactones are represented in the paper. A substantially smaller or larger ring is outside that specific scope and should be treated as a new compatibility question.
- Will the aromatic groups survive each operation? Strongly reactive substituents, additional oxidation-sensitive sites or groups that interfere with nickel coordination may require protection or a different route.
- Can the final C(sp2)–O bond form cleanly? The decarbonylation is the step most directly tied to the specialized nickel/ligand system, so a substrate that forms a difficult aryl–oxygen reductive-elimination intermediate may show lower conversion than the reported examples.
These checks do not replace an experimental screen. They identify where the sequence is likely to fail and which intermediate should be characterized before proceeding.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What the natural-product and pharmaceutical-precursor examples mean
The authors applied the overall sequence to a natural product and to a pharmaceutical precursor. Those demonstrations show that the atom swap can be incorporated into a synthesis containing more than a simple model substrate. They support a claim of synthetic utility: a chemist can use the sequence to alter a complex scaffold at a defined position.
They do not establish pharmacological activity, safety, manufacturing readiness or clinical value. Chemistry World’s 15 February 2022 report described the approach as potentially useful for pharmaceutical intermediates and referred to compounds containing a dibenzoazepine motif. “Potentially useful” is the appropriate level of certainty: the work concerns molecule construction, not drug development. The news coverage is available at Chemistry World.
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Advantages of the sequence compared with designing an ether from scratch
- Retrosynthetic flexibility: A diarylmethane or cyclic ketone precursor can serve as a platform for accessing an oxygen-containing analogue without rebuilding both aryl fragments.
- Late-stage framework editing: The sequence changes a pre-existing carbon framework, which can be useful when much of the target molecule is already assembled.
- Medium-ring coverage: The demonstrated six- to eight-membered lactones show that the approach is not limited to one ring size.
- Mechanistically informed catalysis: Nickel and ligand optimization were connected to the specific challenge of aryl–oxygen reductive elimination rather than selected only by trial and error.
These advantages are strategic rather than absolute. A conventional ether synthesis may still be shorter for a simple target, and every additional operation introduces material use, purification and cumulative yield loss.
Limitations and likely failure points
- Three operations are required. Overall yield is the product of the yields of the oxidation, Baeyer–Villiger rearrangement and decarbonylation. Even strong individual steps can give a modest total yield when multiplied.
- The reported scope is finite. Sixteen examples and 32%–99% yields demonstrate range, but they do not define performance for every substitution pattern, ring size or functional group.
- Regioselectivity can be decisive. An undesired lactone isomer may carry the oxygen to the wrong position for the final diarylether.
- Nickel chemistry may be sensitive to substrate and ligand effects. The need for ligand optimization indicates that the final reductive-elimination step is not a generic property of every nickel catalyst.
- Complex-molecule demonstrations are not process validation. A natural-product or pharmaceutical-precursor example does not provide scale-up data, impurity limits, catalyst-residue specifications or cost analysis.
If a test reaction fails, isolating and analyzing the ketone and lactone intermediates can localize the problem. Failure before lactone formation points toward oxidation or Baeyer–Villiger compatibility; a clean lactone with poor product formation points toward the nickel-catalyzed decarbonylation or the substrate’s aryl–oxygen reductive-elimination step.
How to report the method accurately
A precise description should say that the sequence converts cyclic diarylmethanes or related cyclic diarylketones into cyclic diarylethers through methylene oxidation, Baeyer–Villiger lactonization and nickel-catalyzed lactone decarbonylation. It should identify the 16-example, six- to eight-membered-lactone scope and quote the 32%–99% yield interval as reported results from the 2022 study.
Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Fix the driver behind crashes, sound loss and screen glitches3Repair Windows errors before they cause bigger problemsAvoid saying that nickel directly swaps carbon for oxygen, that all diarylmethanes are suitable, or that the method produces a drug. Those formulations erase the intermediate chemistry and claim evidence the publication does not provide.
Publication and source details
The work is by Quang H. Luu and Junqi Li of the Department of Chemistry at Iowa State University. The primary article, “A C-to-O atom-swapping reaction sequence enabled by Ni-catalyzed decarbonylation of lactones,” appeared in Chemical Science in 2022. The RSC page records first publication on 6 January 2022; PubMed lists the issue date as 26 January 2022. Use the RSC article for the reaction scheme, scope and mechanistic discussion, and the PubMed record for bibliographic confirmation.
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