Electrochemical Oxidation of Abietic and Dehydroabietic Acids for Sustainable Access to C‐7 and C‐15 Oxygenated Abietanes

Abstract

Abietic and dehydroabietic acids are abundant diterpene constituents of gum rosin (colophony) and represent biorenewable feedstocks. While several oxidation strategies have been developed for their methyl ester derivatives, direct oxidation of the naturally occurring free carboxylic acids remains largely unexplored. In this study, we developed electrochemical protocols for the direct oxidation of abietanes at C‐7, enabling the selective synthesis of ketones from naturally occurring abietic and dehydroabietic acids under sustainable conditions. The approach achieves benzylic oxidation of dehydroabietic acid and olefin oxidation of abietic acid, without the need for stoichiometric oxidants or prior esterification steps. The procedures are scalable, operating in both batch and flow electrochemical systems, and have been extended to complex mixtures such as colophony, highlighting their potential for direct valorization of gum rosin feedstocks. Moreover, a complementary mediated electrolysis strategy enables further oxygenation at C‐15, expanding the scope of structural diversification.

Batch and flow electrochemical methods enable direct C‐7 oxidation of abietic and dehydroabietic acids from colophony or their methyl derivatives to the corresponding ketones, while a mediated protocol enables additional C‐15 oxygenation, providing sustainable and selective routes to diversified abietane derivatives.

1. Introduction

Abietane terpenic acids, particularly abietic acid (AA, 1) and dehydroabietic acid (DHA, 2), are major constituents of colophony, a renewable resin derived from coniferous trees, which typically contains 22%–53% AA and 2%–12% DHA [1, 2]. The constituents of this resin are incorporated into diverse products with a wide array of industrial applications, including synthetic rubbers, adhesives, fragrances, and bactericides [3, 4, 5, 6, 7, 8, 9, 10]. Moreover, naturally occurring abietanes, such as 1, have proven valuable as chiral building blocks in the total synthesis of structurally complex and biologically active natural products [11, 12].

Oxygenation of abietanes represents a valuable strategy for accessing synthetically valued colophony‐based products (Figure 1a). Specifically, benzylic C‐H oxidation of methyl dehydroabietate (MDHA, 4) to ketone 5 has been previously achieved using stoichiometric chromium‐based oxidants or transition‐metal catalysts in combination with excess terminal oxidants, such as O₂, H₂O₂, or tert‐butyl hydroperoxide (TBHP) (Figure 1b) [13, 14, 15, 16, 17, 18, 19, 20, 21, 22]. More recently, Lin and co‐workers employed a C‐H functionalization strategy using frustrated radical pairs for the synthesis of ketone 5 [23], while Lubov, Bryliakov, and co‐workers reported the isolation of 5 as a byproduct of a palladium catalyzed C‐H trifluoroethoxylation methodology reported in 2024 [24]. Similarly, olefinic oxidation of methyl abietate (3) to ketone 6 has been reported with stoichiometric iodide reagents or catalytic methyltrioxorhenium in the presence of H₂O₂ (Figure 1c) [25, 26, 27, 28]. Although numerous methods have been developed for the oxidation of abietanes, they often rely on toxic reagents or stoichiometric oxidants, limiting their sustainability [29]. Moreover, these approaches predominantly yield ketones 4 and 6 as the major products, however, additional minor products are frequently detected. Furthermore, the analogous oxidation of the naturally occurring carboxylic acid 2 has received less attention [30], and no methods have been previously reported for the direct oxidation of carboxylic acid 1.

FIGURE 1.

Oxidation of terpenic acids and their corresponding methyl abietates. (a) Electronically activated positions in abietanes. (b) Overview of the reported protocols for the chemical oxidation of methyl dehydroabietate (MDHA, 4). (c) Overview of the reported protocols for the chemical oxidation of methyl abietate (MAA, 3). (d) Overview of the reported protocols for the electrochemical oxidation of methyl dehydroabietate. (e) This work: Electrochemical oxidation of AA (1), DHA (2), MAA (3), and MDHA (4).

Electrochemistry has reemerged as a sustainable and efficient method for driving organic transformations [31, 32, 33, 34, 35, 36, 37, 38, 39]. The use of electrical current to promote oxidation reactions provides an attractive alternative to strong oxidizing agents and large quantities of stoichiometric reagents. Several electrochemical approaches have been developed for benzylic C‐H oxygenation, primarily targeting simple benzylic methylene groups and, to a lesser extent, methyl groups, under diverse electrolysis conditions and oxygen sources [40]. Reported methods include the use of TBHP [41], O₂ [42, 43, 44, 45, 46], or O₂ mediated by pyridine N‐oxides [47], DDQ [48], or [Ph₃C]⁺[B(C₆F₅)₄]⁻ [49]. Water has also been employed as an oxygen source, either through direct electrolysis [50, 51, 52], or in combination with mediators, such as triarylimidazoles [53], TEMPO [54], or Ni(OTf)₂ [55], or by using modified carbon anodes [56]. In addition, methanol has been utilized as an oxygen source, either through direct electrolysis [57] or mediated by KBr [58]. Despite these advances, electrochemical oxidation of abietane frameworks remains underexplored. An electrochemical acetoxylation or oxidation at the C–7 methylene group of abietane 4, as well as a non‐Kolbe‐type electrooxidation of the carboxylic acid 2, that yielded a mixture of alkenes were reported by Torii and co‐workers in 1987 (Figure 1d) [59]. More recently, Liu and co‐workers reported an electrochemical aerobic oxidative cleavage of C‐H bonds in alkylarenes, in which abietane 4 gave the corresponding ketone 5 in 48% yield together with diketone 12 in 12% yield [60].

Developing synthetic organic electrochemical strategies that address sustainability and regioselectivity in abietane oxidation would enable selective and efficient access to high‐value oxygenated abietane derivatives. Although several protocols exist for electrochemical oxidation at benzylic and olefinic positions, the structural complexity of abietanes demands investigation to fine‐tune reactivity and selectivity. Herein, we report the development of direct electrochemical methods, in both batch and flow, for the C‐7 oxidation of abietic and dehydroabietic acids, and their methyl ester derivatives to deliver abietane ketones, was well as mediated electrochemical protocols that afford further C‐15 oxidized products (Figure 1e). Furthermore, these electrochemical protocols could be readily implemented in commercially available flow cells, demonstrating their potential for sustainable scalable synthesis, provided that care is taken regarding the use of lithium perchlorate as a supporting electrolyte, which is potentially explosive.

2. Results and Discussion

To evaluate the electrochemical behavior of the target abietanes, we initiated our study by conducting cyclic voltammetry (CV) experiments for abietanes 1–4. The CV profiles revealed irreversible oxidative events within the electrochemical window of MeCN/n‐Bu₄NBF₄ (Figures S4 and S5). Abietic acid (1) exhibited two oxidative waves at +1.7 and +2.6 V versus Ag/AgCl, whereas dehydroabietic acid (2) displayed two oxidative waves at +1.9 and +2.5 V versus Ag/AgCl. The methyl ester derivatives, 3 and 4, showed similar oxidation potentials relative to their corresponding carboxylic acids. These data indicated that direct electrochemical oxidation of both the acids and the corresponding methyl esters could be achieved at relatively low potentials, informing the design of subsequent preparative electrolysis experiments. We subsequently explored the oxidation of abietanes 1–4 under controlled current electrolysis (CCE) and controlled potential electrolysis (CPE) in a standard undivided IKA ElectraSyn 2.0 cell, employing graphite electrodes (C_gr) as both anode and cathode, with lithium perchlorate in an acetonitrile/water mixture as the supporting electrolyte solution.

2.1. Direct Electrolysis Experiments

Based on previous reports on the chemical oxidation of abietic acid derivatives, we anticipated that electrolysis of 1 and 3 would yield the corresponding unsaturated ketones via olefinic oxidation at C‐7. Under CCE conditions, the reactions of 1 and 3 proved to be poorly selective, likely due to isomerization of the initially formed β,γ–unsaturated ketones (6 and 8) into the corresponding α,β‐unsaturated isomers, followed by further oxidation [27, 28]. In contrast, CPE at 2.4 V versus Ag/AgCl afforded improved selectivity toward the desired ketones, giving the corresponding products in moderate yield (48% yield, Table 1, entries 1 and 3). The use of lower potential (CPE) or lower current (CCE) resulted in lower yields (Table 1, entries 2 and 4).

TABLE 1.

Electrolysis of abietic acid (1) and methyl abietate (3).

Entry	Substratea	Conditions for electrolysis	Product	Yield, %
1	AA (1)	CPE (2.4 V)	8	48
2	AA (1)	CPE (2.0 V)	8	4
3	MAA (3)	CPE (2.4 V)	6	48
4	MAA (3)	CCE (5 mA)b	6	29c

^a Substrate concentration 0.06–0.07 M.

^b 3 F mol⁻¹.

^c Determined by ¹H NMR analysis of the crude reaction mixture using 1,3,5‐trimethoxybenzene as internal standard. CPE, Constant potential electrolysis performed with reference electrode (Ag/AgCl 3 M KCl).

Given the inherent instability of compounds 6 and 8, we conducted hydrogenation reactions to ensure formation of stable derivatives. Thus, Pd/C‐promoted hydrogenation of 6 and 8 afforded the corresponding hydrogenated products, 9 and 10, in 45% and 46% isolated yield, respectively (Scheme 1). These products were fully characterized for the first time, using ¹H, ¹³C NMR, and HRMS. In addition, we have crystallographically characterized 10 [61].

SCHEME 1.

Hydrogenation of abietane ketones 6 and 8.

Next, we investigated the direct electrochemical oxidation of abietanes 2 and 4. Notably, the benzylic oxidation of 2 and 4 proceeded with higher selectivity, and both CCE at 20 mA and CPE at 2.4 V furnished the corresponding ketones 7 and 5 in consistently good yields (up to 87% yield, Table 2, entries 1–9). As observed for 1 and 3, applying lower current (CCE) or lower potential (CPE) resulted in lower yields. Additionally, performing the electrolysis reaction under an inert atmosphere did not significantly impact the yield (69% yield, Table 2, entry 8), whereas, replacing LiClO₄ with n‐Bu₄NBF₄ as the supporting electrolyte resulted in a decrease in yield (16% yield, Table 2, entry 9). These electrolysis conditions were successfully applied to the oxidation of DHA‐enriched colophony (30% DHA), affording the corresponding product 7 in 56% qNMR yield based on DHA content (Table 2, entry 10). Notably, although the Faraday efficiency is lower than that obtained from pure sample of 2, the yield remains comparable, highlighting the feasibility of direct electrochemical valorization of complex natural resins.

TABLE 2.

Electrolysis of dehydroabietic acid (2) and methyl dehydroabietate (4) in batch and flow cells.^a

Entry	Substrate	Conditions for electrolysis	V processed, mLa	SM, %	Product	Yield, %	11, %
1	[2] = 0.03 M	Batch, CCE (20 mA)	10	ND	7	(62)b	ND
2	[2] = 0.03 M	Batch, CCE (5 mA)	10	ND	7	traces	ND
3	[2] = 0.06 M	Batch, CPE (2.4 V)	10	ND	7	65	ND
4	[2] = 0.06 M	Batch, CPE (1.4 V)	10	ND	7	ND	ND
5	[4] = 0.03 M	Batch, CCE (20 mA)	10	ND	5	87	ND
6	[4] = 0.03 M	Batch, CCE (10 mA)	10	ND	5	66	ND
7	[4] = 0.06 M	Batch, CCE (5 mA)	10	ND	5	72	ND
8	[4] = 0.03 M	Batch, CCE (20 mA)c	10	ND	5	69	ND
9	[4] = 0.06 M	Batch, CCE (20 mA)d	10	ND	5	(16)b	ND
10	Colophonye	Batch, CCE (20 mA), 10 F mol−1	10	ND	7	(56)b	ND
11	[4] = 0.05 M	Flow, CCE (10 mA), 100 μL min−1	0.25	82	5	ND	ND
12	[4] = 0.05 M	Flow, CCE (30 mA), 100 μL min−1	0.25	47	5	(34)b	ND
13	[4] = 0.05 M	Flow, CCE (30 mA), 75 μL min−1	0.25	ND	5	(64)b	ND
14	[4] = 0.05 M	Flow, CCE (30 mA), 50 μL min−1	0.25	ND	5	(66)b	ND
15	[4] = 0.05 M	Flow, CCE (50 mA), 100 μL min−1	0.25	10	5	(57)b	ND
16	[4] = 0.05 M	Flow, CCE (30 mA), 50 μL min−1, SS(+)	0.25	93	5	(7)b	ND
17	[4] = 0.05 M	Flow, CCE (20 mA), 50 μL min−1, Pt(+)	0.25	ND	5	(68)b	ND
18	[4] = 0.1 M	Flow, CCE (30 mA), 50 μL min−1	0.25	62	5	(14)b	ND
19	[4] = 0.1 M	Flow, CCE (30 mA), 30 μL min−1	0.25	10	5	(71)b	ND
20	[4] = 0.1 M	Flow, CCE (30 mA), 20 μL min−1	0.25	ND	5	(75)b	11
21	[4] = 0.1 M	Flow, CCE (30 mA), 10 μL min−1	0.25	ND	5	(79)b	24
22	[4] = 0.1 M	Flow, CCE (30 mA), 25 μL min−1	13	ND	5	79 (74)b	ND
23	[2] = 0.1 M	Flow, CCE (30 mA), 25 μL min−1	6.5	ND	7	55 (53)b	ND
24	Colophonye	Flow, CCE (30 mA), 25 μL min−1	6.5	ND	7	55	ND

^a Volume of the reaction mixture processed under the selected electrolysis conditions to generate the results presented herein.

^b Determined by ¹H NMR analysis of the crude reaction mixture using 1,3,5‐trimethoxybenzene as internal standard.

^c Reaction performed under inert atmosphere of nitrogen.

^d n‐Bu₄NBF₄ was used as supporting electrolyte instead of LiClO₄.

^e Colophony enriched in 2 (30%). ND, Not detected by ¹H NMR analysis of the crude reaction mixture. CPE, Constant potential electrolysis performed with reference electrode (Ag/AgCl 3 M KCl).

Transfer of the electrochemical oxidation of abietanes 2 and 4 from batch to single pass continuous flow was explored using two commercially available electrochemical systems: Syrris Asia FLUX and IKA ElectraSyn flow. The initial reaction conditions for electrolysis were based on the batch results and using 4 as the model substrate. Thus, a solution of 4 and LiClO₄ in MeCN/H₂O 94:6 was electrolyzed in an undivided Syrris Asia FLUX flow cell containing a graphite (C_gr) anode and a stainless‐steel (SS) cathode. The best reaction performance was obtained using 0.05 M of 4, at 30 mA of current and 50 or 75 μL min⁻¹, which afforded abietane ketone 5 of up to 68% qNMR yield with full conversion of 4 (Table 2, entries 13–14). Increased flow rate to 100 μL min⁻¹ or decreased current to 10 mA resulted in lower conversion of 4 (up to 57%, Table 2, entries 11–12 and 15). The use of a platinum anode resulted in similar performance (Table 2, entry 17), while the use of a stainless‐steel anode gave only 5% conversion of 4 (Table 2, entry 16). Finally, the best productivity was obtained when the concentration of 4 was increased to 0.1 M, a current of 30 mA, and a flow rate of 25 μL min⁻¹ were used (Table 2, entry 22). Overoxidation reaction, resulting from the benzylic oxidation at C‐15, was, however, observed at lower flow rate of 20 and 10 μL min⁻¹, resulting in formation of 11 of up to 24% yield (Table 2, entries 20–21). Under the optimized conditions, oxidation of 4 afforded 5 in 79% isolated yield (Table 2, entry 22). These electrolysis conditions were successfully transferred to the oxidation of abietane 2, which afforded the corresponding product 7 in 55% isolated yield (Table 2, entry 23). Importantly, the optimized flow conditions were successfully applied to colophony enriched in dehydroabietic acid, with similar outcomes.

Next, we explored the electrolysis of 4 in the commercially available IKA ElectraSyn flow cell, but the performance was found to be irreproducible. Inconsistent conversion and yields were attributed to visible gas evolution, which disrupted the flow in the cell (cell volume ca. 1.2 mL). To overcome this coalescence of hydrogen bubbles, a home‐made PTFE cell gasket with micro channels was employed. This modification enabled systematic optimization of the electrolysis conditions, similar to that achieved with the Syrris system, although full conversion of 4 was not achieved under the investigated conditions (Figures S10–S12).

2.2. Green Metrics Analysis

A qualitative assessment of sustainability metrics suggests that the present protocol is greener than those previously reported, particularly concerning solvent selection, and health and safety profiles of the reagents employed. Furthermore, key green chemistry metrics, including yield, atom economy (AE), reaction mass efficiency (RME), and process mass intensity (PMI), were benchmarked against previously reported oxidation methods (see Tables S13–S16, Supporting Information, for details on quantitative and qualitative green metrics) [62].

In particular, quantitative green metrics analysis of the method developed herein for the oxidation of MDHA demonstrates a high yield combined with excellent atom economy, ouperforming most classical chromium‐based oxidations, which exhibit lower AE values and substantially higher PMI (Figure 2). The moderate RME value (35.5%) determined for the method developed herein is a result of the dual role of water as both reactant and solvent, being employed in relatively large mass compared to the product.

FIGURE 2.

Comparison of green metrics for the oxidation of MDHA (3) between the method developed in this work and previously reported procedures.

As cyclic voltammetry studies revealed that abietane 1 undergoes oxidation at a slightly lower potential than abietane 2, we envisioned that a controlled potential electrolysis (CPE) could be leveraged to achieve selective oxidation within abietane mixtures. To evaluate this possibility, a 2:1 mixture of 1/2 was subjected to CPE at 2.4 V with a total charge of 2 F mol⁻¹. Remarkably, abietane 1 was completely consumed under these conditions, with only abietane 2 remaining in the crude reaction mixture, as confirmed by ¹H NMR analysis. The corresponding oxidation product 8, however, was obtained only in modest yield (14% qNMR yield, Scheme 2), attributed to the earlier evidence that 8 undergoes isomerization and overoxidation under these conditions (Figure S6).

SCHEME 2.

Competitive electrochemical oxidation of abietanes.

2.3. Mediated Electrolysis Experiments

To evaluate if other positions could undergo oxygenation, we explored the ylide‐mediated electrochemical C‐H oxidation of abietanes. We selected ketone 5 as model substrate, a N‐ammonium ylide mediator derived from 2‐(trifluoromethyl)benzohydrazide reported by Kawamata, Neurock, Baran, and co‐workers, and the standard reaction conditions reported by the same authors [63]. Under this standard conditions, abietane 5 was converted into diketone 12 in 58% yield (Table 3, entry 1). This high efficiency was attributed to the presence of the mediator as the yield of 12 decreased to 34% in absence of mediator (Table 3, entry 1). Incomplete conversion and product mixtures were observed when alternative anode materials (C_gr instead of reticulated vitreous carbon, RVC), electrolytes (n‐Bu₄NBF₄ instead of Me₄NBF₄) or solvents (MeCN/water instead of MeCN/HFIP) were used (Table 3, entries 3–6). Finally, as previously reported, we observed that solvent oxygenation played a crucial role in achieving higher yields, with air‐saturated acetonitrile performing best in our setup (Table 3, entry 7).

TABLE 3.

Mediated electrochemical oxidation of dehydroabietic acid.^a

Entry	Deviation from standard conditions	Charge, F mol−1	5, %b	11, %b	12, %b
1	None	6	0	0	58
2	Without mediator	6	Traces	0	34
3	Cgr (+)	6	22	40	14
4	Cgr (+)	12	18	35	30
5	Cgr (+), n‐Bu4NBF4	6	47	36	12
6	MeCN/water (20:1)	6	21	0	23
7	Air‐saturated MeCNc/HFIP	6	0	0	77

^a General conditions: 5 (0.05 M) in MeCN/HFIP 10:1, mediator A (1 equiv.), NaHCO₃ (2.5 equiv.), Me₄NBF₄ (2 equiv.), undivided cell, RVC (+) I Ni (−), 5 mA.

^b Determined by ¹H NMR analysis of the crude reaction mixture using 1,3,5–trimethoxybenzene as internal standard.

^c Acetonitrile previously saturated with air by pumping air through the solvent using an aquarium air pump for 30 min.

We hypothesized that product 11 could serve as an intermediate in the formation of product 12. To test this, 11 was subjected to standard reaction conditions, which indeed afforded 12 in moderate yield. The same conditions were subsequently applied to the oxidation of 7, as well as to the double oxygenation of 4 and 2. In all cases, the corresponding highly oxidized products were obtained in moderate yields (Scheme 3).

SCHEME 3.

Mediated electrochemical oxidation of dehydroabietic acid and methyl dehydroabietate derivatives at C‐7 and C‐15. Standard conditions as depicted in Table 3: RVC(+) I Ni(−), undivided cell, 5 mA, Mediator A (1 equiv.), Me₄NBF₄ (2 equiv.), air‐saturated MeCN/HFIP 10:1.

3. Experimental

3.1. Materials and Methods

All chemicals and solvents were purchased from commercial sources and used without further purification unless otherwise noted. Abietic acid (AA, 1, 80% purity, from Fluorochem, lot FCB065268) and dehydroabietic acid (DHA, 2, 55% purity, from Fluorochem Ltd, lot FCB032360) were purchased. Portuguese Colophony enriched in dehydroabietic acid (lot 3 078/17), derived from Pinus pinea gum, was kindly provided by the Portuguese Association of Distillers and Resin Explorers (Resipinus – Associação de Destiladores e Exploradores de Resina, https://www.resipinus.pt/).

Flash column chromatography was performed using E. Merck silica gel (60, particle size 0.043–0.063 mm). Reactions were monitored by thin layer chromatography (TLC) carried out on 0.25 mm E. Merck silica plates (60F–254), using shortwave UV light and PMA or KMnO₄ stains for visualization. NMR spectra were recorded on a Bruker Fourier 300 spectrometer or Bruker Fourier 400 spectrometer. Determination of conversion, yield and purity of the compounds by NMR was performed using 1,3,5‐trimethoxybenzene as the internal standard. Mass spectra were recorded on a Thermoscientific Exactive Plus spectrometer copulated with Thermoscientific Dionex Ultimate 3000 HPLC. Optical rotation was measured in an Anton Paar MCP 100 polarimeter (measured at 20°C, wavelength 589 nm, cell length 10 mm, concentration reported in g/100 mL, specific rotation reported in ° mL dm⁻¹ g⁻¹).

Reactions were carried out with no precautions to exclude air or moisture, unless otherwise mentioned. Electrolysis reactions and cyclic voltammetry (CV) experiments were carried out with IKA ElectraSyn 2.0 [61].

3.2. General Procedure for the Electrolysis of Abietanes in Batch

Abietane derivative, solvent, and supporting electrolyte were added to an undivided cell (IKA Electrasyn 2.0), equipped with a stir bar at room temperature. The cell was equipped with graphite electrodes as both anode and cathode, and an additional silver reference electrode (Ag/AgCl 3M KCl) for constant potential electrolysis (CPE). Upon completion of the reaction, judged by total charge (F mol⁻¹) and/or TLC, the solvent was removed under reduced pressure. The residue was purified by column chromatography (silica). Alternatively, the yield was determined by ¹H NMR analysis of the crude product before purification.

3.3. General Procedure for Continuous Flow Electrolysis of Abietanes Using the Syrris Flow Cell

A freshly filtered solution of abietane derivative, solvent, and supporting electrolyte was pumped through the Syrris electrochemical flow system. The electrochemical cell was equipped with a stainless‐steel electrode as cathode and graphite, stainless‐steel or platinum coated stainless‐steel as anode, a cell gasket (microflow system), and a cell back‐up seal (Figure S15). The power source was set to the selected constant current, and the reactions were carried out at the specified flow rate with no applied back pressure.

The collection unit was fitted with either an Eppendorf, during reaction condition optimization, or a vial, during long‐run sample collection. For the screening of reaction conditions, 0.5 mL of solution was first passed through the cell with the power source turned off, followed by another 0.5 mL with the power source turned on. These initial volumes were discarded to ensure consistent operating conditions, after which three samples of 0.25 mL were collected under each condition (under steady state). The solvent was removed under reduced pressure, and the residue was purified by column chromatography (silica), or alternatively, yields were determined by ¹H NMR analysis of the crude reaction mixture.

3.4. General Procedure for the Mediated Electrochemical Oxidation of Abietanes

Abietane derivative, solvent, supporting electrolyte, mediator, and base were added to an undivided cell (IKA Electrasyn 2.0), equipped with a stir bar at room temperature. The cell was equipped with graphite or reticulated vitreous carbon (RVC) electrode as anode and nickel electrode as cathode. Upon completion of the reaction, judged by total charge (F mol⁻¹) and/or TLC, the solvent was removed under reduced pressure. The residue was purified by column chromatography (silica).

4. Conclusion

In summary, we present an electrochemical oxidation strategy for the oxygenation of abietane‐type carboxylic acids to access the corresponding C‐7 ketones under both batch and continuous flow conditions. This approach enables the direct use of the naturally occurring carboxylic acid derivatives, thereby circumventing the need of prior esterification steps. Furthermore, we demonstrate that colophony itself can serve as a viable starting feedstock for the preparation of these ketones. In addition, we present a complementary methodology using ylide‐mediated electrochemical oxidation for subsequent oxygenation at the C‐15 position. These methodologies provide selective and versatile tools for upgrading renewable diterpene feedstocks, and we anticipate they will facilitate the synthesis of value‐added abietane derivatives with potential applications in materials and medicinal chemistry.

Supporting Information

Additional supporting information can be found online in the Supporting Information section. The authors have cited additional references within the Supporting Information. The Supporting Information contains general procedures for synthesis of substrates, electrochemical oxidation of abietanes in batch and flow, cyclic voltammetry studies, green metric analysis, and characterization of products by NMR and X‐ray analysis.

Funding

Fundação para a Ciência e a Tecnologia (PTDC/QUI‐QOR/1786/2021; 2022.11562.BD; UID/00100/2025; UID/PRR/100/2025; LA/P/0056/2020; UID/04138/2025); Programa de Desenvolvimento Rural (PDR2020‐101‐032319).

Conflicts of Interest

The authors declare no conflicts of interest.

Supporting information

Supplementary Material