Photocatalytic Strategies for the Synthesis of Xanthates and Their Analogues

Abstract

Sulfur-containing organic molecules, particularly xanthates (dithiocarbonates) and dithiocarbamates, are valuable intermediates in synthetic chemistry and the development of bioactive molecules. For instance, xanthates are potent carbon-radical precursors that can be engaged in diverse transformations, including the 1,2-difunctionalization of alkenes and other functionalizations. However, traditional synthetic methods for these compounds have been limited in efficiency and diversity. This Short Review focuses on novel photochemical procedures for generating xanthates and dithiocarbamates, discussing their advantages and disadvantages. Two main strategies emerge from the literature: (1) Three-component reactions involving the in situ formation of carbodithioate anions, and (2) two-component reactions (direct xanthylation and thiocarbamoylthiolation) using ex situ prepared xanthate and dithiocarbamate sources.

1 Introduction

2 Three-Component Transformations

3 Two-Component Transformations

4 Miscellaneous

5 Conclusion

 

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Key words

xanthates - dithiocarbamates - thioamides - photocatalysis - radicals

1

Introduction

Lilian Geniller (left) earned his M.Sc. in organic chemistry and biomolecules in 2021 from the ENSCM and the University of Montpellier. His M.Sc. thesis, conducted in the research department of Sanofi near Paris, focused on the development of bioactive molecule transformations using dual photoredox/nickel catalysis. In 2024, he obtained his Ph.D. under the supervision of Florian Jaroschik and Alexis Prieto at the ICGM, where he worked on developing novel photomediated processes in organic synthesis. Marc Taillefer (second left) earned his Ph.D. in 1989 from the University Paul Sabatier, Toulouse, under the supervision of Dr. Jean-Jacques Brunet. After a postdoc at the Technische Universität München with Prof. Wolfgang Herrmann, he joined the CNRS in 1992 and became Research Director at the ICGMontpellier. His research focuses on organic synthesis and phosphorus chemistry. For his pioneering work on copper-catalyzed couplings and its worldwide academic and industrial impact, he was awarded the Grand Prix Emile Jungfleisch (French Academy of Sciences) in 2017, and the European Sustainable Chemistry Award (EuChemS) in 2012. He was also president of the French Chemical Society from 2018 to 2021. Florian Jaroschik (second right) obtained his M.Sc. in chemistry from the Universität Regensburg, Germany, in 2004. He then carried out his Ph.D. work in the field of low-valent organolanthanide chemistry under the supervision of Dr. François Nief at the Ecole Polytechnique in Palaiseau, France. After two postdoctoral positions at Monash University, Australia, and at the Université Paris VI, he joined the ICMR, Reims, France, as a CNRS Research Associate in 2009. In 2017, he moved to the ICGM in Montpellier where he currently develops various methodologies in organic synthesis, with a special focus on lanthanide chemistry. Alexis Prieto (right) completed his Ph.D. in 2016 under the co-direction of Nuno Monteiro and Didier Bouyssi at the Université Claude Bernard Lyon 1 (France). Following a one-year period as a post-doc in the group of Paolo Melchiorre (Spain), he joined Emmanuel Magnier and Jérome Hannedouche in Paris for a second post-doc. In 2019, he joined the ICGM, Montpellier, to start his independent career as a CNRS researcher, focusing on the development of novel photomediated processes.

Sulfur-containing organic molecules have attracted considerable attention over the years due to their ubiquity and key roles in natural products,[1] biological processes,[2] and materials science.[3] Among them, compounds featuring an S–C(S) linkage, notably including xanthates (dithiocarbonates) and dithiocarbamates, are of particular interest. These compounds are valuable due to their potential involvement in diverse and promising applications in synthetic chemistry and the development of bioactive molecules.[4] For instance, a large number of xanthates and dithiocarbamates exhibit biological activity, ranging from insecticidal to anticancer properties (Scheme [1]A). Xanthates are particularly notable as versatile intermediates for their ability to generate carbon radicals and undergo a wide range of organic chemical transformations.

Scheme 1 (A) Bioactive xanthates and dithiocarbamates. (B) Reactivities of xanthates and their analogues

For example, Zard and others have showcased the utility of xanthates as carbon radical precursors, especially in the 1,2-difunctionalization of alkenes, forming two new C–C and C–S bonds (Scheme [1]B, top left).[5] Xanthates have also been extensively employed in various reactions such as hydroxylation, vinylation, allylation, azidation, and thiolation (Scheme [1]B, top right).[6] Furthermore, they have been widely used to construct complex molecular scaffolds through radical cyclizations, facilitating the synthesis of a remarkable array of natural products,[7] including aphanorphine,[7a] pleuromutilin,[7d] and lycorane[7e] (Scheme [1]B, bottom). Despite their numerous applications, the use of xanthates and their analogues has historically been restricted to specific substrates due to the low efficiency of their synthetic procedures. Traditionally, xanthate synthesis was limited to metal-free nucleophilic substitution of electrophiles or copper-mediated xanthylation of aryl halides using potassium ethyl xanthate.[5] [8] Meanwhile, conventional synthetic approaches to dithiocarbamates primarily relied on nucleophilic substitution involving thiophosgene, isothiocyanates, and alkyl halides.[9] These methods offered limited diversity in the types of xanthates and dithiocarbamates that could be accessed, thereby constraining their applicability. Consequently, the development of effective and practical synthetic procedures for the preparation of a wide array of xanthates and their analogues is still an active area of research. Over the past five years, the development of novel synthetic routes for the synthesis of such compounds has been explored,[10] especially under photochemical conditions. This Short Review focuses on novel procedures for generating xanthates and dithiocarbamates under photomediated conditions, and discusses the advantages and disadvantages of these methods. The transformations can be classified into two categories: (1) Three-component reactions, which typically involve the in situ formation of anions with an S–C(S) linkage (I, carbodithioates) via reactions between carbon disulfide and nucleophiles (Scheme [2], left), and (2) two-component transformations, which utilize ex situ prepared xanthate or dithiocarbamate sources and primarily involve the formation of intermediates of type II (Scheme [2], right).

Scheme 2 The two main photomediated strategies for the synthesis of xanthates and dithiocarbamates; LG = leaving group

 

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2

Three-Component Transformations

The three-component strategy has been exclusively employed for the photochemical generation of dithiocarbamates. As previously mentioned, this transformation relies on the in situ generation of carbodithioates I, which can further­ function in three distinct ways: (1) as simple nucleophiles, (2) by being oxidized to the corresponding thiyl radicals, or (3) by serving as electron-rich species in the formation of electron donor–acceptor (EDA) complexes (Scheme [3]).

Scheme 3 Reactivities associated with the carbodithioate intermediate

2.1

Carbodithioates as Nucleophiles

Scheme 4 Synthesis of dithiocarbamates via multicomponent reactions

In 2022, He and co-workers reported the synthesis of two classes of dithiocarbamates, 4 and 5, through multicomponent reactions involving α-diazoesters 1, carbon disulfide (2), and amines 3 as starting reagents (Scheme [4]).[11] The nature of the solvent played a crucial role in determining the reaction outcome. While the transformation selectively yielded dithiocarbamates 4 in THF, it primarily led to the formation of dithiocarbamates 5 in 1,4-dioxane. It is worth noting that small quantities of dithiocarbamates 4′ are also formed due to the ring opening of 1,4-dioxane (Scheme [4], gray square). Overall, this strategy provides access only to primary S-alkyl dithiocarbamates or S-benzyl dithiocarbamates, and it is incompatible with the use of primary amines 3.

From a mechanistic perspective, the authors proposed that the reaction would begin with the photoexcitation of α-diazoesters 1, leading to the formation of carbene I through dinitrogen extrusion (Scheme [4]). This intermediate would then be trapped either by the solvent or by the in situ formed carbodithioate II. The pathway involving the solvent would result in the formation of molecules 4 via nucleophilic attack of carbodithioate II onto the zwitterion III. Conversely, the direct reaction with carbodithioate II would lead to the formation of compounds 5.

 

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2.2

Carbodithioates as S-Centered Radical Precursors

Scheme 5 Synthesis of β-keto dithiocarbamates

In 2021, the Singh group reported the synthesis of β-keto dithiocarbamates 9 via a radical functionalization of styrenes 6 in the presence of tert-butyl hydroperoxide (TBHP) under air (Scheme [5]).[12] This approach enabled the generation of a diverse library of compounds 9 using various styrene derivatives, primarily those bearing electron-rich substituents, and amines 8. However, the reaction was limited to the use of secondary amines. Notably, the authors demonstrated that activated styrene derivatives, such as 2-vinylpyridine and 4-nitrostyrene, were sufficiently reactive to undergo thia-Michael additions.

Mechanistically, the authors proposed that the reaction would begin with photoexcitation of the photocatalyst (PC). In its excited state, PC would oxidize the in situ formed carbodithioate I to the thiyl radical II. The resulting PC^•– species would then reduce TBHP, regenerating the ground-state PC and producing the tBuO^• radical. This radical would then react with another molecule of TBHP, generating the radical intermediate III. Concurrently, radical II would react with styrene 6, leading to the formation of intermediate IV. From this intermediate, two pathways have been proposed: (1) Intermediate IV would react first with dioxygen and then with intermediate III, yielding intermediate VI, or (2) intermediate IV would react directly with intermediate III, yielding intermediate VII. Finally, compound 9 would be generated from intermediate VI via a Russell fragmentation, while intermediate VII would afford compound 9 through a Kornblum–DeLaMare rearrangement.

More recently, Sun and co-workers developed a strategy for the synthesis of gem-difluoro quinolin-2(1H)-ones 13 using 2-bromo-2,2-difluoroacetamide reagents 10 in the presence of carbon disulfide (11) and amines 12 (Scheme [6]).[13] The method demonstrated good compatibility with a variety of secondary amines and certain functional groups on the aromatic rings, particularly halides. Similar to Singh’s mechanism (see Scheme [5]), the authors proposed the generation of the key thiyl radical IV from carbodithioate III. The radical IV may then dimerize to form the dithiocarbamate dimer V. The radical intermediate II, which is likely formed by intramolecular cyclization of intermediate I, would then react with the dimer V to afford the product 13 (Scheme [6]).

 

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2.3

Carbodithioates in electron donor–acceptor (EDA) Complexes

Scheme 6 Formation of gem-difluoro quinolin-2(1H)-ones

In recent years, several protocols have emerged for the preparation of dithiocarbamates 17 via the in situ formation of electron donor–acceptor (EDA) complexes, which require the presence of both an electron-rich and an electron-poor species. In the current framework, EDA complex I would be formed between the in situ generated carbodithioate and electron-poor radical precursor 14 (bearing either electron-poor leaving groups (LG) or electron-poor aromatic rings) (Table [1]). The direct photoexcitation of the EDA complex would trigger a single-electron transfer (SET) between the electron-rich and the electron-poor species, yielding the reduced form of molecule 14 and the thiyl radical (intermediate II). Heterolytic cleavage of the C–LG bond would lead to the generation of a carbon radical, which subsequently would couple with the thiyl radical to afford the corresponding dithiocarbamates 17 (Table [1]). The first development highlighting the role of the carbodithioate intermediate in the formation of EDA complexes was reported by Yang’s group (Table [1], entry 1).[14] Indeed, in this study, the authors demonstrated that EDA complexes can be formed between carbodithioates and electron-deficient aryl halides 14a, allowing the formation of S-aryl dithiocarbamates 17. However, while the reaction was highly effective with aryl iodides, it was less productive with aryl bromides and completely ineffective with chlorinated counterparts. Interestingly, during this investigation, the authors found that the use of primary aniline derivatives did not lead to the expected dithiocarbamates 17. Instead, the reactions yielded the corresponding thioureas. After this initial exploration, the same group extended this reactivity to the synthesis of S-alkyl dithiocarbamates 17 by using Katritzky salt 14b (Table [1], entry 2).[15] This reaction primarily provides access to S-alkyl dithiocarbamates 17 derived from stabilized carbon radicals, such as benzyl or α-ester carbon radicals. As previously, the employment of primary aniline or amine derivatives did not afford the expected compounds 17. Subsequently, Wu and Zhang developed an alternative protocol using organothianthrenium salts 14c as electron-poor species in the formation of EDA complexes (Table [1], entry 3).[16] In contrast to previous procedures, this method requires the pre-formation of the carbodithioate species before exposure to light. Compared to the prior work by Yang’s group,[14] [15] this approach allowed the use of substrates 14c with electron-rich aromatic rings, providing the corresponding S-aryl dithiocarbamates 17 in good yields. The main difference can be attributed to the different leaving groups. In Yang’s case (Table [1], entry 1),[14] the formation of the EDA complex is facilitated by electron-deficient aromatic rings. In contrast, in Wu and Zhang’s approach (Table [1], entry 3),[16] the formation of the EDA complex is ensured by the presence of the thianthrenium group. Finally, in 2024, the Yang group reported a one-pot strategy based on the use of organothianthrenium salts 14c, water as the solvent and dodecyltrimethylammonium chloride (DTAC) as a surfactant (Table [1], entry 4).[17]

 

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3

Two-Component Transformations

As previously mentioned, several methods have also been developed for the preparation of xanthates and dithiocarbamates based on the use of ex situ prepared xanthate or dithiocarbamate sources.

Table 1 Carbodithioates in EDA Complexes for the Formation of Dithiocarbamates 17

Entry	Group	14	Conditions	Examples & yields	17 (selected examples)
1	Yang[14]		14a (1 equiv.) 15 (2.7 equiv.), 16 (1.3 equiv.) Cs2CO3 (2 equiv.) 23 W CFL, DMF, RT, 24 h	26 examples 21–81%
2	Yang[15]		14b (1 equiv.) 15 (2.7 equiv.), 16 (1.3 equiv.) Et3N (2 equiv.) 455 nm, water, RT, 24 h	28 examples 55–90%
3	Wu/Zhang[16]		(1) 15 (2 equiv.), 16 (1 equiv.) Na2CO3 (1.1 equiv.), DMSO/H2O (1:1) (2) then 14c (1 equiv.) 420 nm, 35–40 °C, 8 h	27 examples 25–80%
4	Yang[17]		14c (1 equiv.) 15 (3 equiv.), 16 (2 equiv.) K2CO3 (2 equiv.), DTAC(2 wt%) 455 nm, water, RT, 12 h	33 examples 40–91%

3.1

Carbodithioates in EDA Complexes

Building on the same reactivity described above (Table [1]), Wang and co-workers also reported a transformation involving the in situ formation of EDA complexes (Scheme [7]).[18] However, in this method, functionalized dibenzothiophenium salts 18 and ex situ prepared sodium carbodithioate salts 19 were used as starting materials. Overall, this approach yielded a wide array of S-aryl xanthates and dithiocarbamates 20 in moderate to good yields. Remarkably, this method proved effective for the preparation of products 20 derived from relevant pharmaceutical drugs and natural molecules. Interestingly, and in contrast to previously described procedures, this strategy was effective for the synthesis of dithiocarbamates bearing an NH group (Scheme [7]). In this context, it is noteworthy that EDA complexes between preformed carbodithioate salts and redox-active esters have also been employed for C–C bond formation through Giese additions.[19]

Scheme 7 Formation of S-aryl xanthate and dithiocarbamate derivatives

 

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3.2

Direct Xanthylation and Thiocarbamoylthiolation

In 2016, the Alexanian group reported the first direct xanthylation reaction. In this study, the authors explored the C–H xanthylation of alkane derivatives 21 (Scheme [8]).[6d] To achieve this transformation, they synthesized N-xanthylamide 22, which served dual roles in the reaction, acting as both the xanthylating agent and the hydrogen atom transfer (HAT) agent. The specific interest in N-functionalized amides lies in their ability to transfer functional groups and generate amidyl radicals in situ, which can further promote HAT processes, as was previously demonstrated by the same group.[20] However, the main drawback of such reactions is control of the regioselectivity. While the strategy is attractive for generating xanthate compounds 23 from simple, affordable, and abundant alkanes 21, it often results in a mixture of regioisomers (Scheme [8]). However, for specific substrates 21 with hydridic hydrogens (C–H^δ–) or specific conformations, the reaction is fully selective, providing access to single regioisomers. During this study, the authors also demonstrated that xanthates 23 could be converted into various useful compounds, including amines, alcohols, and thioethers. Mechanistically, the reaction would be initiated by photolysis of the N–S bond in molecule 22, producing the amidyl radical I and the thiyl radical II (Scheme [8]). Next, intermediate I would activate the alkane 21 through a HAT event, yielding the carbon radical III. Intermediate IV would subsequently be generated by the addition of intermediate III to compound 22, delivering the xanthate 23 and regenerating the amidyl radical I through a β-scission process.

Scheme 8 The first direct xanthylation process

In 2018, the Alexanian group, in collaboration with the Leibfarth group, extended the C–H xanthylation to polyolefin derivatives (Scheme [9]).[6c] Using this approach, the authors demonstrated that poly(ethylethylene) (PEE) 24 could undergo xanthylation at both primary and secondary sites under blue LED irradiation using N-xanthylamide 22, yielding a mixture of xanthylated-PEEs 25. During their study, they showed that increasing the quantity of 22 directly impacted the rate of xanthylation. For example, using 1 equivalent of 22 per 20 repeat units resulted in only a 3% xanthylation ratio. Increasing the amount of 22 raised the functionalization level to 18% (Scheme [9]). As previously demonstrated, xanthylated-PEE derivatives have also been employed in various post-functionalization reactions, allowing access to diverse polymers that are unattainable through conventional approaches.

Subsequently, Alexanian and co-workers developed a similar approach enabling the synthesis of dithiocarbamates 27 (Scheme [10]).[6b] The strategy involves an intramolecular 1,5-hydrogen atom transfer (HAT) that allows regioselective C–H thiocarbamoylthiolation of various amide derivatives 26, providing access to a wide array of compounds 27 in moderate to good yields. It should be noted that for substrates 26 lacking a hydrogen atom at the 5-position, an intramolecular 1,6-HAT occurred preferentially (Scheme [10], 2nd example). Notably, a thermal version assisted by peroxides was also developed during this study, yielding mostly similar results. However, in certain cases, it proved to be superior to the photochemical method. From a mechanistic perspective, the reaction follows a similar mechanism to that depicted in Scheme [8], except that the intermolecular HAT event is replaced by an intramolecular 1,5-HAT event (Scheme [10]).

Scheme 9 Extension to the C–H xanthylation of a polyolefin

Scheme 10 Intramolecular C–H functionalization for the synthesis of dithiocarbamates

Scheme 11 Intramolecular C–H functionalization for the synthesis of xanthates

More recently, Chen and co-workers extended Alexanian’s prior work to the synthesis of xanthates 29 (Scheme [11]).[21] The reaction follows the same principle as before and involves a key intramolecular 1,5-HAT step. The reaction was successfully performed on various substrates, including aliphatic amides and benzyl amides 28.

Scheme 12 Decarboxylative xanthylation via HAT

Scheme 13 Decarboxylative xanthylation via energy transfer

As previously observed, C–H functionalizations are often poorly selective, yielding a mixture of regioisomers. Therefore, more recent xanthylation and thiocarbamoylthiolation processes have been investigated using pre-functionalized substrates, which offer full control over the selectivity of the functionalization. Within this framework, several decarboxylative procedures have been reported in the literature. The first study related to this strategy was reported by Alexanian and colleagues (Scheme [12]).[6a] In this study, the authors developed a reaction based on the use of N-xanthylamide 31 as the xanthylating agent. Two distinct sets of reaction conditions were employed: (a) a thermal approach requiring a catalytic amount of lauroyl peroxide (DLP) at 80 °C, and (b) a light-initiated approach using blue LEDs at room temperature (Scheme [12]). These reactions enabled the formation of a wide variety of xanthates 32 in moderate to excellent yields, although most examples were obtained using the thermal approach. Unfortunately, no comparison between the two sets of reaction conditions was provided within the scope of the exploration. From a mechanistic perspective, the reaction would follow the previously detailed mechanism (see Scheme [8]), except that the amidyl radical I, generated by thermolysis or photolysis, would abstract a hydrogen atom from carboxylic acid 30 via HAT (Scheme [12]). Interestingly, in this study, the reagent 31 was specifically designed to facilitate the HAT process. Previously employed N-xanthylamide 22 (see Scheme [8]), used for C–H xanthylation, was found to be ineffective for this purpose. This can be mainly explained by the bond-dissociation energy (BDE) of the amide N–H bonds. The BDE of the carboxylic acid O–H bond is around 112 kcal/mol. In contrast, the BDE value of the N–H bond of 22 is approximately 104 kcal/mol, while the BDE of the N–H bond of 31 is around 111 kcal/mol, making the HAT possible.

Scheme 14 Decarboxylative thiocarbamoylthiolation via redox catalysis

In 2024, Prieto’s group developed an alternative protocol in which the decarboxylative xanthylation process proceeded from oxime ester derivatives 33 (Scheme [13]).[22] Using this approach, a large variety of xanthates 35 were obtained in modest to excellent yields, including xanthates derived from natural compounds and drugs. In comparison with Alexanian’s work, this approach is exclusively based on photochemical conditions. Additionally, the use of oxime esters in this reaction allowed for the employment of a simple and readily available xanthylating agent, the xanthate dimer 34 (Scheme [13]). The proposed mechanism is also different, as an energy transfer induces the decarboxylation step. Specifically, the excited PC would transfer energy to substrate 33, triggering N–O bond cleavage and forming radical units I and II. The carbon radical I would then react with dimer 34, resulting in the formation of intermediate III. Through a β-scission process, intermediate III would deliver product 35 along with thiyl radical IV. At this stage, the authors proposed two pathways: either the dimerization of IV, restoring dimer 34, or the trapping of species IV by iminyl radical II, generating intermediate V. Finally, the reaction between intermediate V and carbon radical I would yield product 35 (Scheme [13]).

Independently and concurrently, Dong’s group reported a very similar approach for the synthesis of dithiocarbamates 38 using dithiocarbamate dimer 37 and redox-active esters 36 (Scheme [14]).[23] This photocatalyzed strategy provided access to a wide array of dithiocarbamates 38 in moderate to excellent yields, including derivatives known for their biological activities.

Interestingly, this procedure involves a different mechanistic scenario. The transformation would be initiated by a single-electron transfer (SET) between the excited PC and ester 36, generating both the radical cation PC^•+ and the radical anion I. The latter would then undergo decarboxylation, yielding carbon radical II, which would subsequently add to dimer 37 to form intermediate III. A β-scission process would finally furnish product 38 and thiyl radical IV, which can dimerize to restore 37 (Scheme [14]).

Scheme 15 Synthesis of thioamides through thiocarbamoylation

 

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4

Miscellaneous

In 2024, Wu and colleagues developed a transformation for synthesizing thioamides (Scheme [15]).[24] In this study, the authors prepared a wide variety of thioamides, including both acyclic thioamides 42 (Scheme [15], top-left) and cyclic thioamides 45 and 47 (Scheme [15], top-right). Overall, the three reactions tolerated a broad array of functionalities, providing simple and some complex substrates derived from relevant pharmaceutical drugs in moderate to excellent yields. Compared to the previously mentioned multicomponent synthesis of dithiocarbamates (see Section 2), this strategy is similar, except that the authors used phosphines to perform a desulfurization process.[25] Indeed, the desulfurization step is crucial for generating the key thiocarbamoyl radical intermediate. For the generation of acyclic thioamides 42, the authors proposed the following reaction mechanism (Scheme [15], bottom-left): The in situ formed carbodithioate I is photoexcited under light irradiation, reaching its excited state. In this excited state compound I would act as a potent reductant (*E_1/2 ^Ox (*I/I ^•) ≈ –2.7 V vs SCE), reducing intermediate II, which is formed by the reaction between PCy₃ and carbon disulfide in a polar solvent. This reduction would lead to the formation of radical carbanion III and thiyl radical IV. Subsequently, thiyl radical IV would react with PCy₃, generating intermediate V. A desulfurization step would then afford the thiocarbamoyl radical VI along with SPCy₃. Finally, the radical addition of VI to 41, followed by a reduction–protonation sequence, would yield the product 42. It is noteworthy that the authors proposed species II as an electron mediator because Stern–Volmer experiments showed no fluorescence quenching of the excited carbodithioate I by any of the starting materials used in the transformation.

For the synthesis of molecules 45, a similar mechanism was proposed (Scheme [15], bottom-right). In this case, the excited carbodithioate I would reduce 2-mercaptopyridine (PySH), forming both the PySH^•– radical anion and thiyl radical II. The desulfurization of compound II into intermediate III, assisted by the phosphine, would then occur. Next, a 5-exo-trig cyclization would provide species IV from intermediate III. Finally, IV would be transformed into 45 through HAT with PySH. For the generation of molecules 47, a photocatalytic cycle was proposed in which the thiyl radical II and carbanion VI would be generated by the photocatalyst, and the radical species 46 would be generated through the radical addition of IV onto alkene 46 (Scheme [15], bottom-right).

 

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5

Conclusion

In summary, this Short Review summarizes the ongoing developments of effective and practical synthetic photochemical procedures for xanthates, dithiocarbamates, and thioamides. Recent advancements have primarily focused on two main categories of photochemical synthesis: three-component reactions involving the in situ formation of carbodithioates, and two-component transformations utilizing ex situ prepared xanthate or dithiocarbamate sources. The photochemical methods discussed present exciting avenues for future research, as they address the limitations of traditional synthetic approaches. This progress paves the way for broadening the applicability of these compounds across various domains, from synthetic chemistry to biological fields. However, the valuable synthetic applications of such novel scaffolds featuring an S–C(S) linkage will be fully realized only if effective and milder photochemical processes are developed in the coming years. These processes will be crucial for valorizing these compounds as carbon radical precursors, thereby unlocking their full potential in diverse scientific and industrial applications.

 

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Conflict of Interest

The authors declare no conflict of interest.

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Publication History

Received: 10 December 2024

Accepted after revision: 07 January 2025

Accepted Manuscript online:
07 January 2025

Article published online:
24 February 2025