Catalytic Formylation Strategies in Organic Synthesis

Formylation occupies a central role in organic synthesis as a means to introduce the aldehyde functionality, a versatile handle for further elaboration. Classical electrophilic methods such as Vilsmeier–Haack, Gattermann–Koch, Duff and Reimer–Tiemann reactions employ stoichiometric reagents to generate highly reactive iminium or carbenium intermediates, enabling broad access to aromatic and heterocyclic aldehydes but often at the cost of harsh conditions and significant by-product formation. The advent of transition-metal catalysis has transformed formylation tactics: hydroformylation of alkenes with syngas over rhodium, cobalt or iron centres proceeds under relatively mild conditions to deliver linear and branched aldehydes with high atom economy. More recently, direct C–H activation strategies have harnessed directing groups and carbon monoxide or formic acid surrogates to achieve one-step formylation without pre-functionalisation, thereby streamlining synthetic sequences. Organocatalytic approaches using N-formyl donors, formaldehyde equivalents or formamide derivatives have emerged as metal-free alternatives, while photoredox methods employing CO₂, CO or formate under visible light enable late-stage aldehyde installation in complex molecules. Across these catalytic regimes, continuous improvements in selectivity, enantioselectivity and sustainability are driven by mechanistic insight and computational design, addressing the growing demand for green, scalable routes to fine chemicals, pharmaceuticals and agrochemicals.

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Catalytic Formylation Strategies in Organic Synthesis publication trend

The graph below shows the total number of articles in catalytic formylation strategies in organic synthesis across all publications each year (not limited to Nature Index journals).

Technical terms

Electrophilic formylation: introduction of a –CHO group via stoichiometric, electrophile‐generating reagents.

Hydroformylation: metal‐catalysed addition of syngas (CO/H₂) across alkenes to produce aldehydes.

C–H activation: catalytic cleavage of C–H bonds to enable direct functionalisation.

Formyl group: the aldehydic –CHO moiety, a key intermediate in organic synthesis.

Surrogate reagent: a compound that releases a reactive species (e.g. formaldehyde) in situ under catalytic conditions.

References

1. Formylation of Electron-Rich Aromatic Rings Mediated by Dichloromethyl Methyl Ether and TiCl4: Scope and Limitations. Molecules (2015).
2. Synthesis, Electrochemical and Spectroscopic Characterization of Selected Quinolinecarbaldehydes and Their Schiff Base Derivatives. Molecules (2020).