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Scientific paper
New Reactions of ß-oxo Sulfenyl Chlorides With 2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane-2,4-disulfide and Phosphorus Pentasulfide
Mohamed I. Hegab*
Photochemistry Dept., National Research Centre, Dokki, 12622 Cairo, Egypt.
* Corresponding author: E-mail: apmihegab65@yahoo.com
Received: 03-05-2006
Abstract
2,2-Disubstituted 3-chloro-4-oxochromane-3-sulfenyl chlorides (2a,b) reacted with Lawesson’s reagent (3) to afford the unprecedented 4-oxochromane phosphoro(dithioperoxo)thioic chlorides (5a,b) and not the ß-thiooxo sulfenyl chlorides (6a,b). Whereas, sulfenyl chlorides (2a,b) gave 1,2,5,6-tetrathiocines (7a,b) along with 1,2,3,4-tetrathiins (8a,b) when they were treated with phosphorus pentasulfide. However, chlorination of 1,2,5,6-tetrathiocine (7a) with sulfuryl chloride afforded the 3,4-dichloro-3,4-disulfenyl dichloride (12) along with the 3,4-disulfenyl dichloride (13).
Keywords: 3-Chloro-4-oxochromane-3-sulfenyl chloride, Lawesson’s reagent, tetrathiocine, tetrathiin, disulfenyl chloride.
1. Introduction
ß-Oxo ?-chlorosulfenyl chlorides are versatile intermediates for the formation of ?-chlorosulfenami-des,1,2 thione S-imides,3,4 dithiiranes/thiosulfines,5 thione S-ylides,6 thiapyranes,7 and thiadiazoles.8 Many reactions
of sulfenyl chlorides with nucleophilic reagents, thioketo-nes, 1,3-butadienes, alkenes, disulfides, and with diseleni-des have been reported.9 The formation of a symmetrical cyclic tetrasulfide via the oxidative coupling of dithiol with cesium fluoride-Celite has been also described.10
In the course of continuing study of the chemistry of 3-chloro-2,2-dialkylchroman-4-one-3-sulfenyl chloride, it would be interesting to investigate the chemistry of ß-oxo sulfenyl chlorides 2a,b towards Lawesson’s reagent (LR) and phosphorus pentasulfide.
2. Results and Discussion
Reaction of ß-oxo sulfenyl chlorides 2a,b with LR in 2:1 or 1:1 ratio (see experimental part) in dry toluene under reflux gave, surprisingly, the 4-methoxyphenyl-3-[3-chloro-2,2-disubstituted chromano-4-oxo]phospho-
ro(dithioperoxo)thioic chlorides 5a,b, respectively, and not the 2,2-disubstituted-3-chloro chromano-4-thioxo-3-sulfenyl chlorides 6a,b (see Scheme 1). The formation of phosphorus derivatives 5a,b could be explained presumably, by the addition of the sulfenyl chloride group to the double bond of the phosphorus sulfide of intermediate 4 to leave the carbonyl group inact (see Scheme 2).
The structures of 5a,b were confirmed by the spectroscopic data (IR, 1H,13C, and 31P NMR, and MS) as well as elemental analyses (see Experimental part). The IR spectrum of 5a reveals a strong band at v = 1704 cm–1 for the carbonyl group. 1H NMR spectrum of 5a exhibits for the cyclohexyl protones as a multiplet signal at ? = 1.17–2.47, and methoxy protons at ? = 3.85 as a singlet signal, in addition to the expected aromatic protons. 13C NMR spectrum of 5a adds a good support for the established structure. Whereas, the five cyclohexyl methylene carbons appear at ? = 20.79, 21.17, 24.91, 27.93, and 30.94, which might be, due to the presence of the cyclohexane ring as a chair form. OCH3, C–2, and C–3 atoms are recognized at ? = 55.61, 86.33, and 113.74, respectively. Moreover, 31P NMR spectrum of 5a shows phosporus chemical shift at ? = 88.81.
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SOC12
la,b
2a, b
Cl      LR (3) R,      1:1 or 2:1
Scheme 1
6a,b
S O                     II
ay  s—s—p—R3 N-Cl   Cl
R2
Scheme 2
1H NMR spectrum of 5b exhibits two methyl protons as two singlet signals at ? = 1.72, and 1.80, and signal for methoxy protons at ? = 3.85 as a singlet signal, besides the expected aromatic protons. In fact, products 5a,b exhibited clearly the NMR signals of only one diastereomer (see Experimental part). If the minor dias-tereomer was present, its concentration was too small to be detected. 13C NMR spectrum of 5b reveals two methyl carbons at ? = 22.50, and 24.32. OCH3, C–2, and C–3 carbons are recognized at ? = 55.59, 85.81, and 113.72, respectively. Again, 31P NMR spectrum of 5b shows phosporus chemical shift at ? = 88.60.
The ß-oxo sulfenyl chlorides 2a,b afforded 1,2,5,6-tetrathiocines 7a,b, 1,2,3,4-tetrathiins 8a,b and sulfur when they were heated under reflux with phosphorus pentasulfide in toluene (see Scheme 3). The formation of
7a,b and 8a,b could be explained, presumably, by converting the oxo group of 2 to the thiooxo group to give the unstable ß-thiooxo sulfenyl chloride 6, which further reacts by two alternative pathways: a) the active sulfenyl chloride group of two molecules of 6 could be added to the thiooxo groups via intermolecular addition to give tetrachloro tetrathiocine 9, which loses chlorine gas to afford 7; b) The ß-thiooxo sulfenyl chloride 6 loses chlorine gas to give 1,2-dithiooxo intermediate 10 which is in equilibrium with 1,2-dithiate intermediate 11, and then sulfur could be inserted to 10 or 11 to obtain product 8 (see Scheme 4).
However, chlorination of 7a with sulfuryl chloride (SO2Cl2) in CCl4 afforded 3,4-dichloro-3,4-disulfenyl dichloride 12 along with 3,4-disulfenyl dichloride 13 (see Scheme 3). These products (12 and 13) are stable and
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could be separated by silica gel column chromatography. This is in accordance with literature reports for 1,2-dichloro-1,2-disulfenyl dichlorides.11 The IR spectrum of derivative 7a did not show any absorption band corresponding to the C=O group. 1H NMR spectrum of 7a showed cyclohexyl protons at ? = 1.30–2.03 as a multiplet signal, beside the expected aromatic protons. 13C NMR
spectrum of 7a reveals the chemical shifts for C-2', and C-2" carbons at ô = 80.54, for C-3', and C-3" catrbons at ô = 126.43, and for C-A', and CM" carbons at ô = 128.18. Mass spectrum of 7a showed the prominent ion peak at m/z 458 (M+ - 2SH). :H NMR spectrum of 8a showed only absorptions for cyclohexyl protons and aromatic protons. 13C NMR spectrum of 8a showed
r^N
ci   P2S5
7a
Scheme 3
2a,b
SO2CI2 ,
O
CL      SCI
R/      R
,S—S
s—S
7a,b
Rk      R7
O
^^
SCI
SCI
^^
cl s-s cl
R
C1S    S Cl
R2
P       - 2C1
^
7a,b
^^
Cl,
10
11
Scheme 4
8a,b
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absorptions for C–2´, C–3´, and C–4´ carbons, at ? = 80.76, 125.26, and 137.80 respectively. Mass spectrum of 8a reveals the prominent ion peaks at m/z 326 (M+) and 198. 1H NMR spectrum of 7b reveals the presence of four CH3 protons at ? = 1.58, whereas the 13C NMR of 7b showed signals for four CH3 carbons at ? = 23.01, signals for C–2, and C–2´ carbons at ? = 80.61, for C–3, and C–3´ carbons at ? = 126.43, and for C–4, and C–4´ carbons at ? = 128.16. 1H NMR spectrum of 8b showed absorption for two CH3 groups at ? = 1.65, and 13C NMR spectrum of 8b showed absorption for two CH3 carbons at ? = 22.49, and for C–2, C–3, and C–4 carbons at 80.76, 125.26, and 137.88 respectively.
Spectral data as well as elemental analysis confirmed the structure of 12. 1H NMR spectrum of 12 reveals cyclohexyl protons as multiplet at ? = 1.23–2.22. Actually, 12 exhibited clearly the NMR signals of only one diastereomer (see Experimental part). If the minor diastereomer was present, its concentration was too small to be detected. 13C NMR spectrum of 12 showed C–2´, C–3´, and C–4´ carbons at ? = 87.79, 92.14, and 95.23 respectively. Finally, the 1H NMR spectrum of 13 showed absorption for cyclohexyl protons as multiplet at ? = 1.25–2.223 in addition to the expected aromatic protons. 13C NMR spectrum of 13 reveals C–2´, C–3´, and C–4´ carbons, at ? = 87.90, 113.16, and 114.21 respectively.
3. Experimental
Melting point is uncorrected and recorded on a digital Electrothermal IA 9000 SERIES melting point apparatus (Electro thermal, Essex, U.K.). Microanalyses were performed with all final compounds on Elementar-Vario EL, Microanalytical Unit, Central Services Laboratory, National Research Centre, Cairo, Egypt. The NMR spectra were recorded on a Varian Mercury VX-300 NMR spectrometer. 1H spectra were performed at 300 MHz and 13C NMR spectra at 75 MHz in CDCl3 as solvent. Chemical shifts are quoted in 8 and were related to that of the solvents (Cairo University, Faculty of Science). Splitting patterns were designated as follow: s singlet; d doublet; t triplet; m multiplet. Mass spectra were recorded on Schimadzu GCMS-QP 1000EX (EI, 70 eV) and Hewlett-Packard (EI, 70 eV) spectrometers. IR spectra were obtained with Brucker-Vector 22 for neat samples (for liquids) or KBr wafers (for solid) (Micro-analytical Centre of Cairo University). Compounds la,12 lb,13 2a,b 1 were prepared according to the literature procedures.
Reaction of ß-oxo OC-chloro sulfenyl chlorides (2) with Lawesson’s reagent (3). A mixture of ß-oxo a-chloro sulfenyl chloride 2a or 2b (5 mmol) and Lawesson’s reagent 3 (2.5 or 5 mmol) in 20 ml toluene was refluxed for 6 h. The solution was evaporated under vacu-
um and the crude product was chromatographed on a silica gel column with diethyl ether-petroleum ether (40-60) 1:5 (v:v) as an eluent.
4-Methoxyphenyl-3- [3-chloro spirochroman (2,l')cyclohexane-4-oxo]phosphoro-(dithioperoxo) thioic chloride (5a). Prepared from 2a. Colorless crystals, yield 50%, m.p. 175-176 °C. Anal. Calcd for C21H21Cl2O3PS3 (519.45): C 48.55, H 4.07, Cl 13.65, P 5.96, S 18.52. Found: C 48.38, H 3.89, Cl 13.51, P 5.59, S 18.35. IR (v, cm–1): 1704 (C=O). 1H NMR (CDCl3) 8 1.17-2.47 (m, 10H, cyclohexyl H), 3.85 (s, 3H, OCH3), 6.80-7.07 (m, 4H, Ar H), 7.45-7.56 (m, 1H, Ar H), and 7.60-8.00 (m, 3H, Ar H). 13C NMR (CDCl3) 8 20.79, 21.17, 24.91, 27.93, 30.94, 55.61, 86.33, 113.74, 113.83, 113.97, 114.06, 118.03, 122.16, 129.19, 133.45, 133.64, 136.44, 136.48, 156.46, 163.77, and 188.36. 31P NMR (CDCl3) 8 88.81. EIMS m/z (%): 458 (M+ - 2S, 2Cl37, 6), 456 (M+ - 2S, Cl35, 37, 39), 454 (M+ - 2S, 2Cl35, 45), 419 (55), 265 (12), 233 (13), 213 (15), 205 (100), 173 (21), 155 (12), 121 (37), and 64 (6).
4-Methoxyphenyl-3- [3-chloro 2,2-dimethylchro-mano-4-oxo]phosphoro-(dithiope-roxo)thioic chloride
(5b). Prepared from 2b. Colorless viscous oil, yield 36%. IR (v, cm-1) 1701 (C=O). Anal. Calcd for C18H17Cl2O3PS3 (479.39): C 45.09, H, 3.57, Cl 14.79, P 6.46, S 20.06, Found: C 44.88, H 3.50, Cl 14.65, P 6.25, S 19.80. 1H NMR (CDCl3) 8 1.72 (s, 3H, 2-CH3), 1.80 (s, 3H, 2-CH3), 3.85 (s, 3H, OCH3), 6.80-7.10 (m, 4H, Ar H), 7.40-7.56 (m, 1H, Ar H), and 7.85-8.00 (m, 3H, Ar H). 13C NMR (CDCl3) 8 22.45, 24.25, 55.59, 85.88, 113.72, 113.83, 113.98, 114.04, 118.06, 122.16, 129.18, 133.46, 133.64, 136.44, 136.48, 156.46, 163.78, and 188.36. 31P NMR (CDCl3) 8 88.61. EIMS m/z (%): 419 (M+ - 2S, 2Cl37, 2), 417 (M+ - 2S, Cl35, 37,18), 415 (M+ - 2S, 2Cl35, 100), 381 (20), 379 (56), 225 (13), 193 (14), 173 (15), 155 (12), 121 (100), and 64 (55).
Reaction of ß- oxo OC- chloro sulfenyl chloride 2 with phosphorus pentasulfide. A mixture of ß-oxo a-chloro sulfenyl chloride 2a or 2b (10 mmol) and phosphorus pentasulfide (16 mmol) in 50 ml toluene was heated under refluxe for 10 h. Then the solution was evaporated in vacuo and the crude product was chromatographed on a silica gel column with diethyl ether-petroleum ether (40-60) (1:10) as an eluent to obtain the products (in the order of their elution). Sulfur was separated as first component.
2H, 10H-[l,2,5,6]tetrathiocino[3,4-c:7,8-c']dispi-rochromene-2,l'-cyclohexane (7a). Prepared from 2a. Orange oil, yield 72%. Anal.calcd for C28H28O2S4 (524.76): C 64.08, H 5.38, S 24.44. Found: C 63.78, H 5.28, S 24.05. IR (v, cm–1) 2934, 2859, 1478, 1449, 1272, 1236, 1119, and 755. 1H NMR (CDCl3) 8 1.30-2.03 (m,
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20H, 2-cyclohexyl H), 6.93-6.99 (m, 2H, Ar H), 7.19-7.31 (m, 5H, Ar H), and 7.47-7.50 (m, 1H, Ar H). 13C NMR (CDCl3) 8 21.07, 21.45, 25.20, 32.04, 32.18, 80.54, 116.71, 116.98, 121.42, 126.43, 128.18, 129.48, 129.80, and 151.11. EIMS m/z (%): 458 (M-2SH, 48), 414 (48), 388 (52), 373 (77), 357 (74), 324 (48), 282 (63), 226 (100), 207 (77), 193 (52), and 119 (52).
2H-[l,2,3,4]tetrathiino [5,6-c]spirochromene-2,1-cyclohexane (8a). Prepared from 2a. Yellowish green oil, yield 16%. Anal. Calcd for C14H14OS4 (326.51): C 51.50, H 4.32, S 39.28. Found: C 51.31, H 4.29, S 38.99. IR (v, cm–1): 2935, 2858, 1268, 1250, 1135, and 775. 1H NMR (CDCl3) 8 1.29-1.85 (m, 10H, 2-cyclohexyl H), 6.98- 7.02 (m, 2H, Ar H), 7.20-7.35 (m, 1H, Ar H), and 7.48- 7.52 (m, 1H, Ar H). 13C NMR (CDCl3) 8 21.29, 21.45, 25.03, 32.18, 35.28, 80.76, 116.98, 117.04, 121.42, 121.60, 121.68, 125.26, 137.80, and 151.22. EIMS m/z (%): 326 (M, 10), 294 (23), 230 (16), 198 (13), and 120 (100).
2H, 10H-[l,2,5,6]tetrathiocino[3,4-c:7,8-c']bis-2,2-dimethylchromene (7b). Prepared from 2b. Orange oil, yield 33%. Anal.calcd for C22H20O2S4 (444.64): C 59.42, H 4.53, S 28.84. Found: C 59.03, H 4.48, S 28.53. 1H NMR (CDCl3) 8 1.58 (s, 12H, 4 CH3), 6.94–6.98 (m, 2H, Ar H), 7.20-7.30 (m, 5H, Ar H), and 7.47-7.50 (m, 1H, Ar H). 13C NMR (CDCl3) 8 22.51, 80.54, 116.70, 116.98, 121.42, 126.44, 128.18, 129.44, 129.80, and 151.21. EIMS m/z (%): 378 (M-2SH, 42), 334 (35), 308 (50), 296 (50), 277 (32), 244 (48), and 155 (100).
2H-[l,2,3,4]tetrathiino[5,6-c]-2,2-dimethylchro-mene (8b). Prepared from 2b. Colorless oil, yield 5%. Anal. Calcd for C11H10OS4 (286.45): C 46.12, H 3.52, S 44.77, Found: C 45.87, H 3.48, S 44.45. 1H NMR (CDCl3) 8 1.65 (s, 6H, 2 CH3), 6.99-7.09 (m, 2H, Ar H), 7.20-7.32 (m, 1H, Ar H), and 7.49-7.52 (m, 1H, Ar H). 13C NMR (CDCl3) 8 22.49, 80.76, 116.97, 117.05, 121.42, 121.61, 121.69, 125.26, 137.88, and 151.23. EIMS m/z (%): 286 (M, 5), 254 (20), 190 (16), and 149 (100).
Treatment of tetrathiocine 7a with S02C12. To a
solution of tetrathiocine 7a (1 g, 2 mmol) in CCl4 (10 ml), SO2Cl2 (2 ml in 5 ml CCl4) was added dropwise. The solution was stirred at room temperature for 10h, and solvent evaporated under vacuum at room temperature. The crude product was chromatographed on a silica gel column with diethyl ether : n-hexane (1:20) as an eluent to obtain the products (presented in order of their elution).
3,4-Dichloro-3,4-dichlorosulfenyl spirochroma-ne-2,l'-cyclohexane (12). Yellow oil, yield 19%. Anal. Calcd for C14H14Cl4OS2 (404.20): C 41.59, H 3.49, Cl 35.09, S 15.86. Found: C 41.39, H 3.38, Cl 34.65, S 15.55.
1H NMR (CDCl3) ? 1.23–2.22 (m, 10H, cyclohexyl H), 6.81–6.99 (m, 2H, Ar H), 7.39–7.47 (m, 1H, Ar H), and 7.65–7.85 (m, 1H, Ar H). 13C NMR (CDCl3) ? 21.62, 21.83, 25.11, 27.82, 31.85, 87.79, 92.14, 95.23, 118.00, 119.21, 122.32, 128.73, 136.92, and 156.85. EIMS m/z (%): 410 (M+ Cl35, 3Cl37, 1), 408 [(M+ 2Cl35, 2Cl37, 4), 406 (M+ 3Cl35, Cl37, 16), 404 (M+ 4Cl35, 12), 340 (14), 303 (24), 269 (24), 233 (10), 199 (14), and 64 (100).
2H-3,4-dichlorosulfenyl spirochromene-2,1´-cy-clohexane (13). Yellow oil, yield 23%. Anal. Calcd for C14H14Cl2OS2 (333.28): C 50.45, H 4.23, Cl 21.27, S 19.24. Found: C 50.19, H 4.18, Cl 20.92, S 18.95. 1H NMR (CDCl3) ? 1.25–2.23 (m, 10H, cyclohexyl H), 6.82–6.99 (m, 2H, Ar H), 7.39–7.47 (m, 1H, Ar H), and 7.66–7.85 (m, 1H, Ar H). 13C NMR (CDCl3) ? 21.62, 21.82 25.15, 27.82, 31.85, 87.90, 113.16, 114.21, 117.90, 118.97, 122.32, 128.74, 136.93, and 156.91. EIMS m/z (%): 300 (M – Cl, Cl37, 1), 298 (M – Cl, Cl35, 4), 269 (2), 263 (6), 198 (10), 155 (15), 121 (100), 92 (73), and 64 (40).
4. Conclusion
The unprecedented 4-oxochromane phosphoro (dithioperoxo)thioic chlorides (5) were obtained from 2,2-disubstituted 3-chloro-4-oxochromane-3-sulfenyl chlorides (2) with Lawsson’s reagent (3). 2 reacted with phosphorus pentasulfide to give 1,2,5,6-tetrathiocines (7) in addition to 1,2,3,4-tetrathiins (8). However, 1,2-dichlo-ro-1,2-disulfenyl chloride (12) in addition to 1,2-disul-fenyl chloride (13) were obtained via chlorination of 1,2,5,6-tetrathiocine (7a).
5. References
1. C. D. Gabbutt, J. D. Hepworth, B. M. Heron, M. Kanjia, Tetrahedron 1994, 50, 827–834.
2. K. Oka, S. Hara, Tetrahedron Lett. 1977, 695–698.
3. M. I. Hegab, F. M. E. Abdel-Megeid, F. A. Gad, S. A. Shiba, I. Sotofte, J. Moller, A. Senning, Acta Chem. Scand. 1999, 53, 284–290.
4. M. I. Hegab, F. A. G. El-Essawy, J. Ogaard, I. Sotofte, A. Senning, Sulfur Lett. 2001, 24, 191–196.
5. M. I. Hegab, F. M. E. Abdel-Megeid, F. A. Gad, S. A. Shiba, I. Sotofte, J. Moller, A. Senning,. Acta Chem. Scand. 1999, 53, 133–140.
6. K. Oka, A. Dobashi, S. Hara, Tetrahedron Lett. 1980, 3579–3582.
7. M. I. Hegab, A. A. Amr, F. M. E. Abdel-Megeid, Z. Naturforsch. 2002, 57b, 922–927.
8. M. I. Hegab, N. A. Hassan, E. M. El-Telbani, I. S. Ahmed Farag, F. M. E.Abdel-Megeid, Heteroatom. Chem. 2003, 14, 223–228.
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10. S. T. A. Shah, K. M. Khan, M. Fecker, W. Voelter,        12. H. J. Kabbe, Synthesis 1978, 886–887. Tetrahedron Lett. 2003, 44, 6789–6791.                                       13. F. A. G. El-Essawy, S. M.Yassin, I. A. El-Sakka, A. F.
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Povzetek
V prispevku je predstavljena reakcija 2,2-disubstituiranih 3-kloro-4-oksokroman-3-sulfenil kloridov (2) z Lawessonovim reagentom (3), pri ~emer presenetljivo nastanejo 4-oksokroman fosforo(ditioperokso)tio kloridi (5) in ne -tiookso sulfenil kloridi (6). Nasprotno pa 2 reagira s fosforjevim pentasulfidom in tvori 1,2,5,6-tetratiocine (7) in 1,2,3,4-tetratiine (8). Pri nadalnjem kloriranju 1,2,5,6-tetratiocina (7a) nastaneta 1,2-dikloro-1,2-disulfenil klorid (12) in 1,2-disulfenil klorid (13).
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