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Synlett 2017; 28(08): 957-961
DOI: 10.1055/s-0036-1588140
letter
© Georg Thieme Verlag Stuttgart · New York

Thieme Chemistry Journals Awardees – Where Are They Now?
Molybdenum(V)-Mediated Synthesis of Nonsymmetric Diaryl and Aryl Alkyl Chalcogenides

Peter Franzmann
a   Johannes Gutenberg University Mainz, Institute of Organic Chemistry, Duesbergweg 10-14, 55128 Mainz, Germany   Email: waldvogel@uni-mainz.de
,
Sebastian B. Beil
a   Johannes Gutenberg University Mainz, Institute of Organic Chemistry, Duesbergweg 10-14, 55128 Mainz, Germany   Email: waldvogel@uni-mainz.de
b   Graduate School Materials Science in Mainz, Staudingerweg 9, 55128 Mainz, Germany
,
Peter M. Winterscheid
c   Bonn University, Kekulé Institute of Organic Chemistry and Biochemistry, Gerhard-Domagk-Str. 1, 53121 Bonn, Germany
,
Dieter Schollmeyer
a   Johannes Gutenberg University Mainz, Institute of Organic Chemistry, Duesbergweg 10-14, 55128 Mainz, Germany   Email: waldvogel@uni-mainz.de
,
Siegfried R. Waldvogel*
a   Johannes Gutenberg University Mainz, Institute of Organic Chemistry, Duesbergweg 10-14, 55128 Mainz, Germany   Email: waldvogel@uni-mainz.de
b   Graduate School Materials Science in Mainz, Staudingerweg 9, 55128 Mainz, Germany
› Author Affiliations
Further Information

Publication History

Received: 06 December 2016

Accepted after revision: 09 January 2017

Publication Date:
02 February 2017 (online)

 
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Abstract

Oxidative chalcogenation reaction using molybdenum(V) reagents provides fast access to a wide range of nonsymmetric aryl sulfides and selenides. The established protocol is tolerated by a variety of labile functions, protecting groups, and aromatic heterocycles. In particular, when labile moieties are present, the use of molybdenum(V) reagents provides superior yields compared to other oxidants.


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Key words

molybdenum pentachloride - oxidative coupling - C–S bond formation - cross-coupling - disulfides
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Siegfried R. Waldvogelwas born in Konstanz, Germany, in 1969. He obtained his diploma in chemistry from the University of Konstanz under the supervision of Prof. W. Pfleiderer in 1994. He completed his doctoral research with Prof. M. T. Reetz at the Max Planck Institute for Coal Research in Mülheim in 1996. After a postdoctoral stay at the Scipps Research Institute, La Jolla, California with Prof. J. Rebek, Jr. he started his habilitation at the Westfälische Wilhelms University Münster in 1998. In 2004, he was appointed as associate professor at the Kekulé Institute at the University of Bonn, and in 2010 he was appointed as full professor for Organic Chemistry at the Johannes Gutenberg University Mainz. His research interests include oxidative transformations of arenes with molybdenum(V) reagents and electrochemical methods as well as supramolecular receptor structures for the detection of drugs and explosives. He received the following awards and fellowships throughout his scientific career (selection): Fellowship of the German Scholarship foundation (1990–1994), Kekulé Fellowship (1995–1996), Otto-Hahn-Medal of the Max-Planck-Society (1996), NATO stipend from the DAAD (1997–1998), Liebig Fellowship (1998–2000), Thieme Chemistry Journals Award (2000), Bennigsen-Foerder-Award of the state of North Rhine-Westphalia (2001), Young researchers award of the Förderkreis der Westfälischen Wilhelms Universität (2003), Inventors Award ‘Patente Erfinder’ of the state of North Rhine-Westphalia (2008), Nicolaus-August-Otto-Award of the city of Cologne (2008), and the Zukunftspreis Pfalz Award (2013).

The formation of aryl–chalcogen bonds is a reaction of significant importance in organic synthesis. In particular, nonsymmetric diaryl chalcogenides are highly valuable compounds for biological and pharmaceutical applications.[1] They are part of numerous drugs for the potential treatment of cancer, human immunodeficiency virus (HIV), inflammations, and Alzheimer’s disease (Figure [1]).[2] Furthermore, they serve as unique building blocks for functional materials and as ligands in asymmetric catalysis.[3]

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Figure 1 Bioactive structures involving the diarylsulfide motif

The carbon–chalcogen bond is commonly accessible by two strategies (Scheme [1]): The route 1 involves a transition-metal-catalyzed cross-coupling of an aryl halogenide and a reactive chalcogen intermediate.[4] [5] Secondly, the alternative route 2 exploits oxidative chalcogenation of electron-rich arenes by direct C–H activation in the presence of symmetrical dichalcogenides.[5,6] Since the discovery by Migita and co-workers, the transition-metal-catalyzed C–S cross-coupling reactions have been further improved to access a wide product range in excellent yields.[7] Nevertheless, the substrate scope of those transformations is limited to precursor molecules equipped with leaving groups. In order to overcome this disadvantage, several methods for direct C–H sulfenylation have been recently reported.[8] Those reactions are either carried out employing a stoichiometric amount of an oxidant or by transition-metal catalysis using a co-oxidant. Although these recent developments significantly increased the scope of accessible structures, the number of tolerated functional groups is still highly limited for these protocols. In particular, labile moieties like halides or protecting groups are challenging at the harsh reaction conditions involving high temperatures, long reaction times, or strong oxidants.[9] In contrast, a mild and versatile protocol for oxidative chalcogenation, tolerating a broad scope of functional groups, would be highly desirable.

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Scheme 1 Reaction pathways towards nonsymmetric aryl chalcogenides

Molybdenum pentachloride is a readily available bulk chemical with a strong oxidative power.[10] In combination with its unique Lewis acidic characteristics this leads to very fast substrate transformations.[11] This results in a highly valuable tolerance of acid-sensitive functional groups like iodo,[12] tert-butyl,[13] ketals,[14] or amides.[15] In contrast to other transition-metal-based oxidants, the molybdenum salts formed during the reaction are considered as biocompatible.[16] The performance of MoCl5 can be further enhanced by the addition of Lewis acids like TiCl4.[17] The next generation molybdenum(V) reagent was prepared by substitution of two chlorido ligands by 1,1,1,3,3,3-hexafluoroisopropanolate (HFIP), which significantly reduces the formation of chlorinated byproducts.[18] These molybdenum(V) reagents have shown superior performance for the construction of various five-,[15] [19] six-,[20] seven-,[21] and eight-membered[22] ring systems compared to other oxidants.

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Scheme 2 Oxidative chalcogenation of 1,3,5-trimethoxybenzene with different dichalcogenides. a Mesitylene was used instead of 4.

Here, we report a highly versatile and valuable molybdenum(V)-mediated oxidative chalcogenation of highly functionalized arenes as substrates. Initially, we studied the influence of different dichalcogenides onto the sulfenylation of 1,3,5-trimethoxybenzene (Scheme [2]). The amounts of reagents as well as the reaction times were elucidated by GC-supported optimization. The dichalcogenides 5 were synthesized by the oxidation of the corresponding thiols by iodine.[23] Our results reveal that the electron-withdrawing or electron-releasing character of the substituent has no major influence on the oxidative sulfenylation. As targeted, we were able to obtain products including labile moieties like iodo in 6e in good yields. Moreover, the synthetic protocol turned out to be suitable for aliphatic disulfides and selenium derivatives (6g and 6h). Although full conversion of the dichalcogenides was observed, we did not reach quantitative yields due to the formation of nonidentified byproducts (polymers, oligomers), which are easily separated during workup. The lower yields of product 6d and 6g are attributed to the lower reactivity of the components employed (5d and 5g), which results in prolonged reaction times and the increased formation of byproducts. While disulfide 5d can be transformed into a thianthrene species, which has been described previously,[23] the yield of 6g is diminished due to chlorination. Therefore, we performed this synthesis using MoCl3(HFIP)2 as a more elaborated reagent. The yield was almost doubled up to 45%. This demonstrates the superior reactivity and selectivity of the second generation molybdenum(V) reagent.

Secondly, the sulfenylation reaction was performed with di(p-tolyl)disulfide (5b). A scope of ten different diarylsulfides with sophisticated substitution patterns was obtained in moderate to good yields (Scheme [3]). The molybdenum(V)-mediated sulfenylation tolerates different protecting groups for phenols or amines as well as labile moieties such as tert-butyl or iodo groups. Furthermore, we have shown that the synthetic protocol is suitable for heterocyclic substrates such as indoles or benzofuranes.

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Scheme 3 Oxidative aryl-sulfenylation of different aromatic substrates

In order to verify the superior performance compared to other oxidants we studied the oxidative sulfenylation of 2-bromo-5-iodoanisole (Table [1]). Other oxidants result in an increased formation of byproducts and therefore lower yields. These byproducts are mostly formed by protodehalogenation of the labile iodo moiety. A milder oxidant like I2/DMSO is not capable to form the desired product. The oxidative sulfenylation with TiCl4 as a sole reagent was also not successful, which reveals that MoCl5 acts as the oxidant in the reaction, while TiCl4 only serves as an additive to decrease chlorination. This is in complete accordance to previous mechanistic studies.[24]

Table 1 Comparison of Different Oxidants

Entry

Reagent[8] [9] [25]

Temp (°C)

Time

Yield (%)

1

MoCl5/TiCl4

22

15 min

52

2

DDQ/MeSO3H

22

15 min

43

3

FeCl3

22

15 min

37

4

K2S2O8/TFA

22

16 h

17

5

I2/DMSO

80

 3 h

 0

6

TiCl4

22

15 min

 0

Previous studies by Yoshida and co-workers indicate that the initial step in the oxidative sulfenylation reaction is the formation of an (RS)3 + species (Scheme [4]).[26] This intermediate can be attacked by an activated arene as nucleo­phile to form the desired product after subsequent proton extrusion and re-aromatization. According to the oxidation potentials of similar substrates described in the literature, an initial oxidation of the aromatic substrate is also plausible.[27] Since we only observed the formation of thianthrenes as byproducts, but no biaryl species, it is more likely that the reaction occurs according the mechanism described by Yoshida and co-workers.

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Scheme 4 Plausible mechanistic rationale for the molybdenum(V)-mediated sulfenylation

In conclusion, we established a novel protocol for molybdenum(V)-mediated oxidative sulfenylation reactions.[28] [29] [30] [31] The synthesis is reliable, easy to perform, and provides moderate to good yields. Various labile moieties like iodo groups or protecting groups are tolerated in the oxidative coupling reaction. The use of molybdenum(V) as an oxidant provides superior yields compared to other reagents in the presence of labile functional groups. The method is highly complementary to other reagents described. Furthermore, we were able to obtain several molecular structures by X-ray analysis of suitable single crystals.


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Acknowledgment

The authors thank the German Research Foundation DFG (WA 1276/15-1) for financial support. S.B.B. gratefully acknowledges support by a Kekulé fellowship of the Fonds der Chemischen Industrie (FCI).

Supporting Information

    Supporting information for this article is available online at http://dx.doi.org.accesdistant.sorbonne-universite.fr/10.1055/s-0036-1588140.
  • Supporting Information

  • References and Notes

  • 5 Drabowicz J, Kielbasínski P, Zajac A, Wach-Panfilow P. Synthesis of Sulfides, Sulfoxides and Sulfones . In Comprehensive Organic Synthesis . Vol. 6. Knochel P, Molander GA. Elsevier; Amsterdam: 2014: 131
    CrossrefSearch in Google Scholar
  • 6 Tran LD, Popov I, Daugulis O. J. Am. Chem. Soc. 2012; 134: 18237
    CrossrefPubMedSearch in Google Scholar
    • 11a Schubert M, Waldvogel SR. Eur. J. Org. Chem. 2016; 1921
    • 11b Waldvogel SR, Trosien S. Chem. Commun. 2012; 48: 9109
      CrossrefPubMedSearch in Google Scholar
    • 11c Kramer B, Fröhlich R, Bergander K, Waldvogel SR. Synthesis 2003; 91
    • 12a Waldvogel SR, Aits E, Holst C, Fröhlich R. Chem. Commun. 2002; 1278
    • 12b Mirk D, Kataeva O, Fröhlich R, Waldvogel SR. Synthesis 2003; 2410
      Thieme Connect
  • 13 Mirk D, Wibbeling R, Fröhlich R, Waldvogel SR. Synlett 2004; 1910
  • 14 Waldvogel SR, Fröhlich R, Schalley CA. Angew. Chem. Int. Ed. 2000; 39: 2472
    CrossrefPubMedSearch in Google Scholar
  • 15 Franzmann P, Trosien S, Schubert M, Waldvogel SR. Org. Lett. 2016; 18: 1182
    CrossrefPubMedSearch in Google Scholar
  • 16 Yamamoto A, Honma R, Sumita M. J. Biomed. Mater. Res. 1998; 39: 331
    CrossrefPubMedSearch in Google Scholar
  • 17 Kramer B, Fröhlich R, Waldvogel SR. Eur. J. Org. Chem. 2003; 3549
  • 18 Schubert M, Leppin J, Wehming K, Schollmeyer D, Heinze K, Waldvogel SR. Angew. Chem. Int. Ed. 2014; 53: 2494
    CrossrefPubMedSearch in Google Scholar
    • 19a Schubert M, Wehming K, Kehl A, Nieger M, Schnakenburg G, Fröhlich R, Waldvogel SR. Eur. J. Org. Chem. 2016; 60
    • 19b Trosien S, Böttger P, Waldvogel SR. Org. Lett. 2014; 16: 402
      CrossrefPubMedSearch in Google Scholar
  • 21 Kramer B, Waldvogel SR. Angew. Chem. Int. Ed. 2004; 43: 2446
    CrossrefPubMedSearch in Google Scholar
  • 22 Kramer B, Averhoff A, Waldvogel SR. Angew. Chem. Int. Ed. 2002; 41: 2981
    CrossrefPubMedSearch in Google Scholar
  • 23 Spurg A, Schnakenburg G, Waldvogel SR. Chem. Eur, J. 2009; 15: 13313
    CrossrefPubMedSearch in Google Scholar
  • 24 Leppin J, Schubert M, Waldvogel SR, Heinze K. Chem. Eur. J. 2015; 21: 4229
    CrossrefPubMedSearch in Google Scholar
  • 26 Matsumoto K, Kozuki Y, Ashikari Y, Suga S, Kashimura S, Yoshida J.-I. Tetrahedron Lett. 2012; 53: 1916
    CrossrefSearch in Google Scholar
    • 27a Zweig A, Hodgson WG, Jura WH. J. Am. Chem. Soc. 1964; 86: 4124
      CrossrefSearch in Google Scholar
    • 27b Appendix B: Tables of Physical Data. In Fundamentals and Applications of Organic Electrochemistry: Synthesis, Materials, Devices. Vol. 1. Fuchigami T, Inagi S, Atobe M. John Wiley and Sons; Chichester: 2015: 217
      Search in Google Scholar
  • 28 General Protocol of the Disulfide Synthesis (A) A solution of the given thiol (1.0 equiv) in pyridine was treated with iodine (0.66 equiv) and stirred for the given time (15–30 min) at r.t. at argon atmosphere. Subsequently, water was added, and the mixture was extracted with EtOAc. The combined organic layers were washed with brine, dried over MgSO4, and the solvent was evaporated. The crude product was purified as described below.
  • 29 General Protocol of the Oxidative Coupling Reaction Using Mo(V) Reagents (B) A solution of the disulfide 5 (1.0 equiv) in anhydrous CH2Cl2 was treated with TiCl4 (3.3 equiv) and subsequently MoCl5 (3.0 equiv) or with MoCl3(HFIP)2 (3.0 equiv). Subsequently, a solution of the aromatic compound (5.0 equiv) in anhydrous CH2Cl2 was added dropwise,e and the mixture was stirred for the given time (10–60 min) at r.t. at argon atmosphere. After completion of the reaction, a sat. aq solution of NaHCO3 was added and it was stirred for additional 5 min. The mixture was extracted with CH2Cl2, washed with brine, dried over MgSO4, and the solvent was evaporated. The crude product was purified as described below.
  • 30 Bis(4-iodophenyl)disulfide (5e) According to the protocol for the disulfide synthesis (A), 4-iodothiophenol (0.50 g, 2.12 mmol) was treated with iodine (0.36 g, 1.40 mmol) in pyridine (20 mL) for 15 min. The crude product was filtered through a pad of silica (eluent: cyclohexane–EtOAc, 9:1) to yield compound 5e as a colorless solid (0.44 g, 88%). 1H NMR (400 MHz, CD2Cl2): δ = 7.65–7.62 (m, 4 H), 7.25–7.21 (m, 4 H). 13C NMR (101 MHz, CD2Cl2): δ = 138.7, 137.2, 129.9, 93.0. HRMS (APCI+): m/z calcd for C12H8I2S2 [M]•+: 469.8151; found: 469.8160.
  • 31 4-Methylphenyl-5′-bromo-2′-iodo-4′-methoxyphenylsulfide (8f) According to the protocol for the oxidative coupling reaction (B), bis(4-methylphenyl)disulfide (5b, 0.20 g, 0.81 mmol) was treated with TiCl4 (0.51 g, 2.68 mmol) and MoCl5 (0.66 g, 2.44 mmol) in anhydrous CH2Cl2 (20 mL). Subsequently, 2-bromo-5-iodoanisole (7f, 1.27 g, 4.06 mmol) in anhydrous CH2Cl2 (10 mL) was added dropwise, and the reaction mixture was stirred for 15 min. After the described workup, the crude product was purified by flash column chromatography (eluent: cyclohexane–EtOAc, 99:1) and recrystallized from MeOH (approx. 15 mL, 65 → 4 °C) to yield compound 8f as a colorless solid (0.37 g, 52%); mp 135.2–136.7 °C. 1H NMR (400 MHz, CD2Cl2): δ = 7.38 (s, 1 H), 7.32 (s, 1 H), 7.32–7.20 (m, 2 H), 7.18–7.16 (m, 2 H), 3.87 (s, 3 H), 2.34 (s, 3 H). 13C NMR (101 MHz, CD2Cl2): δ = 155.8, 138.7, 135.5, 134.5, 131.9, 131.9, 130.9, 123.5, 113.1, 101.4, 57.3, 21.4. HRMS (ESI+): m/z calcd for C14H12OS79BrI [M + H]+: 434.8915; found: 434.8924.

  • References and Notes

  • 5 Drabowicz J, Kielbasínski P, Zajac A, Wach-Panfilow P. Synthesis of Sulfides, Sulfoxides and Sulfones . In Comprehensive Organic Synthesis . Vol. 6. Knochel P, Molander GA. Elsevier; Amsterdam: 2014: 131
    CrossrefSearch in Google Scholar
  • 6 Tran LD, Popov I, Daugulis O. J. Am. Chem. Soc. 2012; 134: 18237
    CrossrefPubMedSearch in Google Scholar
    • 11a Schubert M, Waldvogel SR. Eur. J. Org. Chem. 2016; 1921
    • 11b Waldvogel SR, Trosien S. Chem. Commun. 2012; 48: 9109
      CrossrefPubMedSearch in Google Scholar
    • 11c Kramer B, Fröhlich R, Bergander K, Waldvogel SR. Synthesis 2003; 91
    • 12a Waldvogel SR, Aits E, Holst C, Fröhlich R. Chem. Commun. 2002; 1278
    • 12b Mirk D, Kataeva O, Fröhlich R, Waldvogel SR. Synthesis 2003; 2410
      Thieme Connect
  • 13 Mirk D, Wibbeling R, Fröhlich R, Waldvogel SR. Synlett 2004; 1910
  • 14 Waldvogel SR, Fröhlich R, Schalley CA. Angew. Chem. Int. Ed. 2000; 39: 2472
    CrossrefPubMedSearch in Google Scholar
  • 15 Franzmann P, Trosien S, Schubert M, Waldvogel SR. Org. Lett. 2016; 18: 1182
    CrossrefPubMedSearch in Google Scholar
  • 16 Yamamoto A, Honma R, Sumita M. J. Biomed. Mater. Res. 1998; 39: 331
    CrossrefPubMedSearch in Google Scholar
  • 17 Kramer B, Fröhlich R, Waldvogel SR. Eur. J. Org. Chem. 2003; 3549
  • 18 Schubert M, Leppin J, Wehming K, Schollmeyer D, Heinze K, Waldvogel SR. Angew. Chem. Int. Ed. 2014; 53: 2494
    CrossrefPubMedSearch in Google Scholar
    • 19a Schubert M, Wehming K, Kehl A, Nieger M, Schnakenburg G, Fröhlich R, Waldvogel SR. Eur. J. Org. Chem. 2016; 60
    • 19b Trosien S, Böttger P, Waldvogel SR. Org. Lett. 2014; 16: 402
      CrossrefPubMedSearch in Google Scholar
  • 21 Kramer B, Waldvogel SR. Angew. Chem. Int. Ed. 2004; 43: 2446
    CrossrefPubMedSearch in Google Scholar
  • 22 Kramer B, Averhoff A, Waldvogel SR. Angew. Chem. Int. Ed. 2002; 41: 2981
    CrossrefPubMedSearch in Google Scholar
  • 23 Spurg A, Schnakenburg G, Waldvogel SR. Chem. Eur, J. 2009; 15: 13313
    CrossrefPubMedSearch in Google Scholar
  • 24 Leppin J, Schubert M, Waldvogel SR, Heinze K. Chem. Eur. J. 2015; 21: 4229
    CrossrefPubMedSearch in Google Scholar
  • 26 Matsumoto K, Kozuki Y, Ashikari Y, Suga S, Kashimura S, Yoshida J.-I. Tetrahedron Lett. 2012; 53: 1916
    CrossrefSearch in Google Scholar
    • 27a Zweig A, Hodgson WG, Jura WH. J. Am. Chem. Soc. 1964; 86: 4124
      CrossrefSearch in Google Scholar
    • 27b Appendix B: Tables of Physical Data. In Fundamentals and Applications of Organic Electrochemistry: Synthesis, Materials, Devices. Vol. 1. Fuchigami T, Inagi S, Atobe M. John Wiley and Sons; Chichester: 2015: 217
      Search in Google Scholar
  • 28 General Protocol of the Disulfide Synthesis (A) A solution of the given thiol (1.0 equiv) in pyridine was treated with iodine (0.66 equiv) and stirred for the given time (15–30 min) at r.t. at argon atmosphere. Subsequently, water was added, and the mixture was extracted with EtOAc. The combined organic layers were washed with brine, dried over MgSO4, and the solvent was evaporated. The crude product was purified as described below.
  • 29 General Protocol of the Oxidative Coupling Reaction Using Mo(V) Reagents (B) A solution of the disulfide 5 (1.0 equiv) in anhydrous CH2Cl2 was treated with TiCl4 (3.3 equiv) and subsequently MoCl5 (3.0 equiv) or with MoCl3(HFIP)2 (3.0 equiv). Subsequently, a solution of the aromatic compound (5.0 equiv) in anhydrous CH2Cl2 was added dropwise,e and the mixture was stirred for the given time (10–60 min) at r.t. at argon atmosphere. After completion of the reaction, a sat. aq solution of NaHCO3 was added and it was stirred for additional 5 min. The mixture was extracted with CH2Cl2, washed with brine, dried over MgSO4, and the solvent was evaporated. The crude product was purified as described below.
  • 30 Bis(4-iodophenyl)disulfide (5e) According to the protocol for the disulfide synthesis (A), 4-iodothiophenol (0.50 g, 2.12 mmol) was treated with iodine (0.36 g, 1.40 mmol) in pyridine (20 mL) for 15 min. The crude product was filtered through a pad of silica (eluent: cyclohexane–EtOAc, 9:1) to yield compound 5e as a colorless solid (0.44 g, 88%). 1H NMR (400 MHz, CD2Cl2): δ = 7.65–7.62 (m, 4 H), 7.25–7.21 (m, 4 H). 13C NMR (101 MHz, CD2Cl2): δ = 138.7, 137.2, 129.9, 93.0. HRMS (APCI+): m/z calcd for C12H8I2S2 [M]•+: 469.8151; found: 469.8160.
  • 31 4-Methylphenyl-5′-bromo-2′-iodo-4′-methoxyphenylsulfide (8f) According to the protocol for the oxidative coupling reaction (B), bis(4-methylphenyl)disulfide (5b, 0.20 g, 0.81 mmol) was treated with TiCl4 (0.51 g, 2.68 mmol) and MoCl5 (0.66 g, 2.44 mmol) in anhydrous CH2Cl2 (20 mL). Subsequently, 2-bromo-5-iodoanisole (7f, 1.27 g, 4.06 mmol) in anhydrous CH2Cl2 (10 mL) was added dropwise, and the reaction mixture was stirred for 15 min. After the described workup, the crude product was purified by flash column chromatography (eluent: cyclohexane–EtOAc, 99:1) and recrystallized from MeOH (approx. 15 mL, 65 → 4 °C) to yield compound 8f as a colorless solid (0.37 g, 52%); mp 135.2–136.7 °C. 1H NMR (400 MHz, CD2Cl2): δ = 7.38 (s, 1 H), 7.32 (s, 1 H), 7.32–7.20 (m, 2 H), 7.18–7.16 (m, 2 H), 3.87 (s, 3 H), 2.34 (s, 3 H). 13C NMR (101 MHz, CD2Cl2): δ = 155.8, 138.7, 135.5, 134.5, 131.9, 131.9, 130.9, 123.5, 113.1, 101.4, 57.3, 21.4. HRMS (ESI+): m/z calcd for C14H12OS79BrI [M + H]+: 434.8915; found: 434.8924.

   Permissions and Reprints All articles of this category
Zoom Image
Siegfried R. Waldvogelwas born in Konstanz, Germany, in 1969. He obtained his diploma in chemistry from the University of Konstanz under the supervision of Prof. W. Pfleiderer in 1994. He completed his doctoral research with Prof. M. T. Reetz at the Max Planck Institute for Coal Research in Mülheim in 1996. After a postdoctoral stay at the Scipps Research Institute, La Jolla, California with Prof. J. Rebek, Jr. he started his habilitation at the Westfälische Wilhelms University Münster in 1998. In 2004, he was appointed as associate professor at the Kekulé Institute at the University of Bonn, and in 2010 he was appointed as full professor for Organic Chemistry at the Johannes Gutenberg University Mainz. His research interests include oxidative transformations of arenes with molybdenum(V) reagents and electrochemical methods as well as supramolecular receptor structures for the detection of drugs and explosives. He received the following awards and fellowships throughout his scientific career (selection): Fellowship of the German Scholarship foundation (1990–1994), Kekulé Fellowship (1995–1996), Otto-Hahn-Medal of the Max-Planck-Society (1996), NATO stipend from the DAAD (1997–1998), Liebig Fellowship (1998–2000), Thieme Chemistry Journals Award (2000), Bennigsen-Foerder-Award of the state of North Rhine-Westphalia (2001), Young researchers award of the Förderkreis der Westfälischen Wilhelms Universität (2003), Inventors Award ‘Patente Erfinder’ of the state of North Rhine-Westphalia (2008), Nicolaus-August-Otto-Award of the city of Cologne (2008), and the Zukunftspreis Pfalz Award (2013).
Zoom Image
Figure 1 Bioactive structures involving the diarylsulfide motif
Zoom Image
Scheme 1 Reaction pathways towards nonsymmetric aryl chalcogenides
Zoom Image
Scheme 2 Oxidative chalcogenation of 1,3,5-trimethoxybenzene with different dichalcogenides. a Mesitylene was used instead of 4.
Zoom Image
Scheme 3 Oxidative aryl-sulfenylation of different aromatic substrates
Zoom Image
Scheme 4 Plausible mechanistic rationale for the molybdenum(V)-mediated sulfenylation