Article pubs.acs.org/OPRD
Multigram Scale Syntheses of First and Second Generation of Trifluoromethanesulfenamide Reagents Quentin Glenadel,† Sébastien Alazet,† François Baert,† and Thierry Billard*,†,‡ †
Institute of Chemistry and Biochemistry (ICBMS − UMR CNRS 5246), Univ Lyon, Université Lyon 1, CNRS, 43 Bd du 11 novembre 1918, F-69622 Villeurbanne, France ‡ CERMEP − In Vivo Imaging, Groupement Hospitalier Est, 59 Bd Pinel, F-69003 Lyon, France S Supporting Information *
ABSTRACT: Trifluoromethanesulfenamide reagents constitute a family of very efficient reagents to trifluoromethylthiolate various molecules. Optimized syntheses have been developed to easily obtain, in a reproducible manner, large quantities of these reagents, with good overall yields. Up to 84 g have already been obtained, at a reasonable cost.
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toxicity of the historical reagent CF3SCl.30 Therefore, some new efficient reagents and methods have emerged these last years to propose to the chemist community convenient tools to easily prepare various CF3S molecules.17,31−36 Among all of these new reagents, trifluoromethanesulfenamides (BB reagents, Figure 2), developed in our laboratory, appeared as very efficient and versatile reagents allowing either electrophilic or nucleophilic trifluoromethylthiolations.37−41
INTRODUCTION Since a long time, fluorinated compounds have always known a particular attention, essentially because of the specific intrinsic properties of fluorine atom.1−12 With time, this interest has constantly grown to reach, these last years, its paroxysm with the development of new original and efficient methods to synthesize fluorinated compounds.13−18 This availability of new synthetic strategies has largely contributed to the development of new fluorinated groups with various specific properties, finding applications in a large panel of various fields. In particular, association of fluorinated moieties with heteroatoms turned out very interesting because of the extraordinary properties brought by such substituents.16,17,19−21 Among these new moieties, the trifluoromethylsulfanyl group (CF3S) has recently emerged. This infatuation is notably justified by its specific electronic properties (Hammett constants σp = 0.50, σm = 0.40; Swain−Lupton constants F = 0.36, R = 0.14)22 and its high lipophilicity (Hansch parameter πR = 1.44).23−25 Furthermore, some CF3S molecules have found pertinent applications in life sciences (Figure 1).26−29 Such an interest in trifluoromethylthiolated compounds has required the development of new methods to synthesize these targeted products, but above all, the design of new trifluoromethylthiolating reagents to circumvent the high
Figure 2. Trifluoromethanesulfenamide reagents (BB reagents). In parentheses, the CAS Registry Number is shown.
Consequently, because of the increasing use of these reagents, large-scale production appeared to be essential.
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RESULTS AND DISCUSSION The syntheses of these reagents are based on the specific rearrangement of the corresponding trifluoromethanesulfinamidines (1) arising from the reaction of Ruppert−Prakash reagent with DAST and a primary amine (Scheme 1). In the case of BB13 and BB23, a postmethylation is then performed.42 Synthesis of BB13H. In this case, the trifluoromethanesulfinamidine (1a) obtained after addition of aniline is very sensitive, and the acidity of the reaction medium is strong enough to induce, in situ, the rearrangement into BB13H. Consequently, the expected reagent is directly obtained after Received: March 1, 2016
Figure 1. Some bioactive CF3S molecules. © XXXX American Chemical Society
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DOI: 10.1021/acs.oprd.6b00062 Org. Process Res. Dev. XXXX, XXX, XXX−XXX
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Scheme 1. Synthetic Scheme of Trifluoromethanesulfenamides
Table 2. Methylation of BB13H To Provide BB13 entry
BB13H (g)
1a 2 3
2.80 3.00 1.00
4
1.00
5 6b
0.50 17.00
base (g) NaH (0.70) NaH (0.75) i-PrNEt2 (0.74) i-PrNEt2 (0.74) K2CO3 (0.72) NaH (3.87)
methylating reagent (g) MeI (2.71) MeI (2.96) MeI (0.81)
TfOMe (0.51) MeI (13.74)
i-PrNEt2 (g)
aniline (g)
BB13H (quantity/ yield)
1 2 3 4 5a
0.28 2.13 7.12 14.22 14.24
0.35 2.66 8.84 17.73 17.80
0.26 1.94 6.49 12.93 12.95
0.19 1.40 4.69 9.31 9.28
0.30 g (79%) 2.58 g (89%) 8.68 g (89%) 15.42 g (80%) 17.00 g (88%)
a
b
Use of a
mechanical stirring seems to improve the yield. It is important to notice that BB13H and BB13 are relatively volatile and require the use of pentane as chromatographic solvent and evaporation under moderate controlled vacuum (110 mbar, at 25 °C). Synthesis of BB23. The second generation of trifluoromethanesulfenamides (BB23) is in general more reactive,39 and to this day it constitutes the most used reagent of this family. Consequently, its production at a large scale, still bigger than for BB13, was highly expected. The synthesis of this reagent requires a supplementary step because the intermediate trifluoromethanesulfinamidine (1b), arising from tosylamide, is stable and cannot be rearranged during the first step. Consequently, 1b must be transformed into corresponding trifluoromethanesulfenamide (BB23H) under acidic conditions, before the methylation step (Scheme 2).
Table 1. Multigram Synthesis of BB13H DAST (g)
16.40 g (90%)
Without chromatographic purification of BB13H. mechanical stirrer.
aniline addition. The production of this first reagent has been scaled up to 17 g without major issues, following the initially described procedure (Table 1).42 It is noteworthy that no
CF3SiMe3 (g)
2.40 g (80%) 2.74 g (85%)
TfOMe (0.93)
a
entry
BB13 (quantity/ yield)
Use of a mechanical stirrer.
diminution of yields was observed by increasing the starting material quantity. On the contrary, generally, better yields were obtained. With the biggest quantity, the amount of final product slightly decreases with a standard magnetic stirrer (entry 3), whereas an optimal yield is obtained under mechanical stirring, certainly due to a more efficient stirring, and species diffusion, with larger volume. It is noteworthy that the low temperature (−20 °C) is necessary to well control the first step and to observe an optimal formation of the transient difluoro(trifluoromethyl)-λ4sulfanamine without degradation. Concerning the use of iPrNEt2, a previous study42 has demonstrated that other tertiary amines (pyridine, 2,6-lutidine, triethylamine) could be also used, but in general, better results were observed with Hünig’s base. Other sources of “CF3−” species have been also screened. In particular, fluoral hemiaminals,43,44 arising from trifluoroacetaldehyde or fluoroform, trifluoroacetamides,45,46 arising from trifluoroacetic acid, or trifluoromethanesulfinamides,47,48 arising from trifluoromethanesulfinate, have been tested without success. Synthesis of BB13. Initially, the methylation step had been performed with NaH and MeI. To try to avoid the manipulation of large amount of NaH, a few other systems has been tested (Table 2). Nevertheless, by using a less strong base, such as iPrNEt2 or K2CO3, no methylation has been observed, even with stronger methylating agent or by heating the reaction medium. In the initial published procedure, BB13H was obtained relatively clean after the first step, and no further purification was performed before the methylation step. However, several attempts have shown that not only the methylation yield was slightly lower but that the final BB13 product was of lesser quality, even after purification. Consequently, it is recommended to systematically purified BB13H by chromatography before the methylation step. Finally, on multigram scale, the methylation works well, and up to 17 g of final product BB13 could be obtained. Again, a
Scheme 2. Synthesis of Trifluoromethanesulfenamide BB23
First, scale-up of the synthesis of 1b has been studied (Table 3). The solubility of tosylamide is a major issue in this multigram extrapolation. Indeed, if with a small amount, a homogeneous Table 3. Synthesis of Trifluoromethanesulfinamidine 1b entry
CF3SiMe3 (g)
DAST (g)
iPrNEt2 (g)
tosylamide (g)
1b (quantity/ yield)
1 2 3 4 5 6a 7a 8a 9a
4.90 6.92 8.64 16.61 16.65 4.15 41.52 41.52 45.67
6.11 7.85 10.77 20.71 20.76 5.18 51.79 51.78 56.96
4.45 6.29 7.85 15.10 13.13 3.77 37.74 37.74 41.51
5.90 10.00 10.40 20.00 20.05 5.00a 50.00a 50.00a 55.00a
10.88 g (92%) 15.10 g (91%) 14.87 g (71%) 35.30 g (88%) 28.79 g (72%) 8.76 g (88%) 87.60 g (88%) 83.00 g (83%) 95.00 g (86%)
a
B
Solid addition of tosylamide. DOI: 10.1021/acs.oprd.6b00062 Org. Process Res. Dev. XXXX, XXX, XXX−XXX
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solution in ethyl acetate is easy to obtain in reasonable volume (entry 1), with larger quantities tosylamide must be solubilized in hot solution, to minimize the added volume of solvent, and this final solution must be kept warm during the dropwise addition. By the way, this technical issue is source of variability in the observed yields (entries 2−3 and 4−5). To better control this critical addition, a solid addition has been envisaged. To validate this modification, the reaction has been first performed in small scale (entry 6). The obtained results are in accordance with the previous “liquid addition” (entry 1). Then, this strategy has been scaled up to 50 g of starting tosylamide with good, and reproducible, results (entries 7−8). To this day, this method has allowed the production of 95 g of 1b in one batch, with good yields (entry 9). It is noteworthy that, from the experience acquired from BB13 synthesis, this step has been systematically performed under mechanical stirring as, also, the following steps. The rearrangement in acidic conditions of 1b has been, next, optimized (Table 4).
In general, NaH, as s base, did not lead to satisfactory yields, whatever the methylating agent. Even if satisfactory results have been obtained with NaH/Me2SO4 system on a 6 g scale (entry 4), lower, unsatisfactory yields were systematically obtained at a larger scale (entries 5−6). If iPrNEt2/MeI system leads to a disappointing result (entry 7), with the iPrNEt2/TfOMe system, excellent, and reproducible, results were obtained whatever the starting quantities (from 7 to 91 g). It is noteworthy that TfOMe must be added rapidly following the deprotonation (around 5 min after) because of the relative instability of deprotonated species. In a practical point of view, during the synthesis of BB23 reagent, the chromatographic purification of intermediates 1b is highly recommended to achieve optimal yields. However, BB23H is only purified by trituration with pentane before to be engaged in last step. Financial Estimations for Reagent Production. To this day, we have been able to produce 17 g of BB13H, nearly 17 g of BB13 and 84 g of BB23 with respective overall yields 88%, 79% and 72%. The production of BB23 in similar amounts is now an implemented routine in the laboratory. We have tried to determined the cost of these batches. To perform such analysis, we have taken in consideration the reagents, the solvents used for reactions, extractions and purifications, the silica for chromatography, and the drying agent (MgSO4), and we have also estimated the acetone volume used for cleaning (Table 6).
Table 4. Acidic Rearrangement of 1b To Provide BB23H entry
1b (g)
acid (g)
1 2 3 4 5 6
25.76 34.60 23.14 80.00 96.40 120.60
CF3CO2H (30.02) CF3CO2H (40.33) H2SO4 (23.20) H2SO4 (79.60) H2SO4 (95.92) H2SO4 (120.00)
BB23H (quantity/yield) 19.20 24.50 17.73 61.43 74.44 91.00
g g g g g g
(94%) (89%) (97%) (97%) (97%) (95%)
Table 6. Estimated Costs of BB Reagents BB (batch)
The acidic treatment of 1b led to BB23H with good reproducible yields at around 30 g scale (entries 1−2). Nevertheless, to try to reduce costs at larger scale, trifluoroacetic acid has been successfully substituted by less expensive sulfuric acid (entry 3). In a larger scale, excellent yields were obtained (entries 4−6), with, to this day, a one-batch production of 91 g of BB23H. The last step to obtain the expected BB23 reagent is the methylation of the previous BB23H. Before, to extrapolate to large quantities, some optimizations have been performed to determine the best methylating system in this case (Table 5).
BB23H (g)
1 2 3 4 5 6 7
0.50 0.50 0.50 6.00 9.20 18.60 0.50
8
7.00
9
10.93
10
19.20
11
74.00
12
91.00
base (g) NaH (0.08) NaH (0.08) BuLi (0.12) NaH (1.06) NaH (1.63) NaH (3.23) i-PrNEt2 (0.27) i-PrNEt2 (3.67) i-PrNEt2 (5.73) i-PrNEt2 (10.06) i-PrNEt2 (38.78) i-PrNEt2 (47.69)
methylating reagent (g)
BB23 (quantity/ yield)
MeI (0.35) TfOMe (0.33) TfOMe (0.30) Me2SO4 (3.63) Me2SO4 (5.56) Me2SO4 (11.24) MeI (0.28)
0.29 g (55%) 0.30 g (57%) 0.15 g (29%) 5.00 g (79%) 4.9 g (51%) 10.10 g (52%) 0.09 g (16%)
TfOMe (4.66)
7.01 g (95%)
TfOMe (6.94)
10.50 g (91%)
TfOMe (12.78)
18.10 g (90%)
TfOMe (47.00)
69.70 g (90%)
TfOMe (57.80)
84.22 g (88%)
cleaning acetonea
silicaa + MgSO4a
“chemical cost” 10.90 €/g 11.86 $/gb 18.90 €/g 20.57 $/gb 8.00 €/g 8.71 $/gb
BB13H (7 g)
41 €
23 €
7€
5€
BB13 (7 g)
51 €
60 €
12 €
9€
BB23 (63 g)
419 €
60 €
15 €
15 €
a
Negotiated prices with chemical suppliers. bExchange rate on 03/01/ 16, 07:46 UTC.
Surprisingly, despite a lower step number, the first generation of trifluoromethanesulfenamide reagents (BB13H and BB13B) is more expensive than the second generation (BB23). This is mainly due to the pentane, used for chromatographic purifications, which is a more expensive solvent than cyclohexane, used for BB23. Nevertheless, globally the cost per gram of these reagents stays reasonable.
Table 5. Methylation of BB23H To Provide BB23 entry
reagentsa solventsa
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CONCLUSION To conclude, the production of trifluoromethanesulfemanide reagents has been optimized to be scaled-up on multigram scale, up to 84 g for the second generation. Nevertheless, this quantity does not constitute an upper limit, and larger quantities should be obtained with these optimized conditions, with good overall yields. Furthermore, the estimated costs are really reasonable and clearly compatible with low cost applications of these reagents. These efficient conditions open the way to easy syntheses of large amounts of these reagents by any research laboratories for further applications. This should contribute to the development of chemistry around these reagents in the future and to popularize their use. C
DOI: 10.1021/acs.oprd.6b00062 Org. Process Res. Dev. XXXX, XXX, XXX−XXX
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EXPERIMENTAL SECTION Synthesis of N-[(Trifluoromethyl)sulfanyl]aniline (BB13H). A dry 500 mL, three-necked, round-bottomed flask equipped with a thermometer and a mechanical stirrer was charged with diisopropylethylamine (12.95 g, 1.0 equiv) and anhydrous dichloromethane (200 mL) under nitrogen. The resulting mixture was cooled to −20 °C, and DAST (17.80 g, 1.1 equiv) was added dropwise keeping the temperature between −20 °C and −10 °C. Ten minutes after the end of the addition, TMSCF3 (14.24 g, 1.0 equiv) was added dropwise keeping the temperature between −20 °C and −10 °C. After the end of the addition, the reaction mixture was stirred at −20 °C for 1 h. Aniline (9.28 g, 1.0 equiv) was added keeping the temperature between −20 °C and −10 °C, and then the reaction mixture was allowed to warm to room temperature. After 15 hours, the conversion of aniline was checked by TLC (pentane/acetone: 98:2). The reaction mixture was washed with water. Layers were separated, and the aqueous layer was extracted with dichloromethane. The combined organic layers were washed with saturated aqueous ammonium chloride, water, and brine, dried over MgSO4, filtered, and concentrated to dryness. The crude residue was finally purified by flash chromatography (pentane/acetone: 100/0 to 98/2) to afford BB13H (17 g, 88%, colorless liquid). 1 H NMR (400 MHz, CDCl3) δ = 7.32 (m, 2H), 7.11 (m, 2H), 7.02 (m, 1H), 5.08 (br, 1H). 13C NMR (101 MHz, CDCl3) δ = 145.2, 129.5 (q, 3J(C,F) = 317 Hz), 129.4, 122.0, 115.2. 19F NMR (376 MHz, CDCl3) δ = −52.89 (s, 3F). Synthesis of N-Methyl-N-[(trifluoromethyl)sulfanyl]aniline (BB13). A dry 500 mL, three-necked, round-bottomed flask equipped a thermometer and a mechanical stirrer was charged with sodium hydride (60% dispersion in mineral oil) (3.87 g, 1.1 equiv) and anhydrous DMF (200 mL) under nitrogen. The suspension was cooled to −20 °C a solution of BB13H (17 g, 1.0 equiv) in anhydrous DMF (100 mL) was added dropwise keeping the temperature between −20 °C and −10 °C. Ten minutes after the end of the addition, iodomethane (13.74 g, 1.1 equiv) was added dropwise keeping the temperature between −20 °C and −10 °C. The suspension was stirred at −20 °C for 30 min and then allowed to warm to room temperature. After 4 h, the conversion of BB13H was checked by TLC (pentane 100%). The reaction mixture was partitioned between pentane and water, and the aqueous layer was extracted with pentane. The combined organic layers were washed with water and brine, dried over MgSO4, filtered, and concentrated to dryness. The crude residue was finally purified by flash chromatography (pentane 100%) to afford BB13 (16.40 g, 90%, colorless liquid). 1 H NMR (400 MHz, CDCl3) δ = 7.31 (m, 2H), 7.24 (m, 2H), 6.97 (tt, J = 7.4, 1.2 Hz, 1H), 3.50 (d, J = 0.9 Hz, 3H). 13C NMR (101 MHz, CDCl3) δ = 148.8, 130.5 (q, 3J(C,F) = 321 Hz), 129.1, 121.3, 116.1, 46.3. 19F NMR (376 MHz, CDCl3) δ = −50.35 (s, 3F). Synthesis of (E)-N,N-Diethyl-1,1,1-trifluoro-N-(4-methylbenzenesulfonyl) methanesulfinimidamide (1b). A dry 2-L, four-necked, round-bottomed flask equipped with a thermometer and a mechanical stirrer was charged with diisopropylethylamine (41.51 g, 1.0 equiv), anhydrous dichloromethane (650 mL) and anhydrous ethyl acetate (320 mL) under nitrogen. The resulting mixture was cooled to −20 °C, and DAST (56.96 g, 1.1 equiv) was added dropwise keeping the temperature between −20 °C and −10 °C. Ten minutes
after the end of the addition, TMSCF3 (45.67 g, 1.0 equiv) was added dropwise keeping the temperature between −20 °C and −10 °C. After the end of the addition, the reaction mixture was stirred at −20 °C for 1 h, and solid tosylamide (55.0 g, 1.0 equiv) was added, via a funnel, under nitrogen gas counter-flow. The suspension was stirred at −20 °C for 1 h and then allowed to warm to room temperature. After 15 hours, the conversion of tosylamide was checked by TLC (cyclohexane/ethyl acetate: 7:3). The reaction mixture was washed with water and brine. The organic layer was dried over MgSO4, filtered, and concentrated to dryness. The crude residue was finally purified by flash chromatography (cyclohexane/ethyl acetate: 80/20 to 75/25) to afford 1b (95.0 g, 86%, brown liquid). 1 H NMR (400 MHz, CDCl3) δ = 7.74 (m, 2H), 7.23 (d, J = 7.8 Hz, 2H), 3.33 (dq, J = 14.4, 7.2 Hz, 2H), 3.22 (dq, J = 14.4, 7.2 Hz, 2H), 2.36 (s, 3H), 1.12 (t, J = 7.2 Hz, 6H). 13C NMR (101 MHz, CDCl3) δ = 142.6, 140.5, 129.4, 126.2, 123.2 (q, 3 J(C,F) = 328 Hz), 42.5 (br), 21.5, 13.3. 19F NMR (376 MHz, CDCl3) δ = −68.72 (s, 3F). Synthesis of 4-Methyl-N-[(trifluoromethyl)sulfanyl]benzene-1-sulfonamide (BB23H). A 2-L, four-necked, round-bottomed flask equipped with a thermometer and a mechanical stirrer was charged with 1b (120.6 g, 1.0 equiv) and dichloromethane (700 mL). The resulting mixture was cooled to 0 °C, and sulfuric acid 95% (120 g, 3.3 equiv) was added dropwise keeping the temperature between 0 and 10 °C. After the end of the addition, the reaction mixture was allowed to warm to room temperature. After 2 h, the conversion of 1b was checked by TLC (cyclohexane/ethyl acetate: 8:2). The reaction mixture was washed with water. Layers were separated, and the aqueous layer was twice extracted with dichloromethane. The combined organic layers were washed with brine, dried over MgSO4, filtered, and concentrated to dryness. The crude residue was finally triturated with pentane for 2 h, and the resulting suspension was filtered and rinsed with pentane to afford BB23H (91.0 g, 95%, off white solid). 1 H NMR (400 MHz, CDCl3) δ = 7.80 (m, 2H), 7.34 (d, J = 8.0 Hz, 2H), 6.73 (s, 1H), 2.44 (s, 3H). 13C NMR (101 MHz, CDCl3) δ = 145.3, 135.1, 130.0, 128.1 (q, 3J(C,F) = 315 Hz), 127.9, 21.8. 19F NMR (376 MHz, CDCl3) δ = −51.41 (s, 3F). Synthesis of N-4-Dimethyl-N-[(trifluoromethyl)sulfanyl]benzene-1-sulfonamide (BB23). A dry 2-L, three-necked, round-bottomed flask equipped with a thermometer and a mechanical stirrer was charged with BB23H (91.0 g, 1.0 equiv) and anhydrous dichloromethane (700 mL) under nitrogen. The resulting mixture was cooled to 0 °C, and diisopropylethylamine (47.69 g, 1.1 equiv) was added dropwise keeping the temperature between 0 and 5 °C. Five minutes after the end of the addition, MeOTf (57.80 g 1.05 equiv) was added dropwise keeping the temperature between 0 and 5 °C. After the end of the addition, the reaction mixture was stirred at 0 °C for 30 min, and the conversion of BB23H was checked by TLC (cyclohexane/ethyl acetate: 8:2). The reaction mixture was washed with water and brine. The organic layer was dried over MgSO4, filtered, and concentrated to dryness. The crude residue was finally purified by flash chromatography (cyclohexane/ethyl acetate: 99:1 to 96:4) to afford BB23 (84.22 g, 88%, light yellow solid). 1 H NMR (400 MHz, CDCl3) δ = 7.75 (m, 2H), 7.35 (m, 2H), 3.31 (s, 3H), 2.44 (s, 3H). 13C NMR (101 MHz, CDCl3) δ = 145.1, 134.3, 130.1, 129.0 (q, 3J(C,F) = 316 Hz), 127.9, 43.8, 21.7. 19F NMR (376 MHz, CDCl3) δ = −50.34 (s, 3F). D
DOI: 10.1021/acs.oprd.6b00062 Org. Process Res. Dev. XXXX, XXX, XXX−XXX
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(27) Coleman, N.; Nguyen, H. M.; Cao, Z.; Brown, B. M.; Jenkins, D. P.; Zolkowska, D.; Chen, Y.-J.; Tanaka, B. S.; Goldin, A. L.; Rogawski, M. A.; Pessah, I. N.; Wulff, H. Neurotherapeutics 2015, 12, 234. (28) Houston, M. E., Jr; Vander Jagt, D. L.; Honek, J. F. Bioorg. Med. Chem. Lett. 1991, 1, 623. (29) Sato, D.; Kobayashi, S.; Yasui, H.; Shibata, N.; Toru, T.; Yamamoto, M.; Tokoro, G.; Ali, V.; Soga, T.; Takeuchi, T.; Suematsu, M.; Nozaki, T. Int. J. Antimicrob. Agents 2010, 35, 56. (30) Stump, E. C. Chem. Eng. News 1967, 45, 44. (31) Boiko, V. N. Beilstein J. Org. Chem. 2010, 6, 880. (32) Tlili, A.; Billard, T. Angew. Chem., Int. Ed. 2013, 52, 6818. (33) Toulgoat, F.; Alazet, S.; Billard, T. Eur. J. Org. Chem. 2014, 2014, 2415. (34) Lin, J.-H.; Ji, Y.-L.; Xiao, J.-C. Curr. Org. Chem. 2015, 19, 1541. (35) Zhang, K.; Xu, X.; Qing, F. Youji Huaxue 2015, 35, 556. (36) Zheng, H.; Huang, Y.; Weng, Z. Tetrahedron Lett. 2016, 57, 1397. (37) Billard, T. In Encyclopedia of Reagents for Organic Synthesis [O nline]; J ohn Wiley & Sons Ltd., 2015, 10.1002/ 047084289X.rn01828. (38) Billard, T. In Encyclopedia of Reagents for Organic Synthesis [O nline]; J ohn Wiley & Sons Ltd., 2014, 10.1002/ 047084289X.rn01763. (39) Glenadel, Q.; Alazet, S.; Billard, T. J. Fluorine Chem. 2015, 179, 89. (40) Glenadel, Q.; Alazet, S.; Tlili, A.; Billard, T. Chem. - Eur. J. 2015, 21, 14694. (41) Glenadel, Q.; Bordy, M.; Alazet, S.; Tlili, A.; Billard, T. Asian J. Org. Chem. 2016, 5, 428. (42) Ferry, A.; Billard, T.; Langlois, B. R.; Bacque, E. J. Org. Chem. 2008, 73, 9362. (43) Billard, T.; Bruns, S.; Langlois, B. R. Org. Lett. 2000, 2, 2101. (44) Billard, T.; Langlois, B. R.; Blond, G. Tetrahedron Lett. 2000, 41, 8777. (45) Jablonski, L.; Joubert, J.; Billard, T.; Langlois, B. R. Synlett 2003, 230. (46) Joubert, J.; Roussel, S.; Christophe, C.; Billard, T.; Langlois, B. R.; Vidal, T. Angew. Chem., Int. Ed. 2003, 42, 3133. (47) Inschauspe, D.; Sortais, J.-B.; Billard, T.; Langlois, B. R. Synlett 2003, 233. (48) Roussel, S.; Billard, T.; Langlois, B. R.; Saint-Jalmes, L. Synlett 2004, 2119.
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.oprd.6b00062. 1 H, 13C, and 19F NMR spectra (PDF)
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AUTHOR INFORMATION
Corresponding Author
*E-mail address:
[email protected]. Author Contributions
Q.G. and S.A. contributed equally. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS We thank the CNRS and the French Ministry of Research for their financial support. We also thank the French Fluorine Network for its support.
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ABBREVIATIONS DAST, (diethylamino)sulfur trifluoride; Tf, trifluoromethanesulfinyl; TLC, thin layer chromatography; TMS, trimethylsilyl REFERENCES
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DOI: 10.1021/acs.oprd.6b00062 Org. Process Res. Dev. XXXX, XXX, XXX−XXX
