Mercapto-compounds are important intermediates in organic synthesis,dye,and are widely used for the synthesis of medicines, polymeric materials,aluminum alloy corrosion inhibitors and analytical reagents for heavy metal ion complexation ^{[1, 2]}. Moreover,sulfur-containing compounds are widely used spices in food flavor and play an important role in improving the quality and grade of flavors ^{[3, 4]}. So,a great number of studies have appeared on sulfur-containing compounds ^[5]. In this paper,we first synthesized 1,3-diphenylpropane-2,2-dithiol using 1,3-diphenyl-2-propanone as the starting material. Several related novel compounds (3a-3c, 4a-4c) were then also synthesized. The procedures required only mild reaction conditions and simple protocols but gave high yields. The crystal structure of compound 4a was determined by X-ray diffraction. The synthetic route to produce compounds 3-4 is shown in Scheme 1.

Scheme 1

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Scheme 1. Synthetic route of compounds 3a-3c and 4a-4c.

Infrared spectra were measured on a Nicolet 360 FT-IR instrument using KBr pellet in the 4000-400 cm^-1 range.¹H NMR spectra were collected on a Mercury Plus-400 MHz spectrometer in DMSO-d₆ solution with TMS as an internal standard. Elemental analysis was performed by a Vario EL III elementary analysis instrument. Melting point was measured on a XT4A melting-point apparatus with microscope and uncorrected. Single crystal X-ray diffraction data were collected on a BRUCKER SMART APEX-CCD diffractometer equipped with a graphite-monochromatic Mo K_α radiation (λ= 0.71073 Å ). 1,3-Diphenyl-2-propanone and other chemicals were purchased from commercial sources.

A solution of 0.01 mol of iodine in 50 mL of benzene was added, with stirring,to 0.01 mol of 1,3-diarylpropane-2,2-dithiol (2)in 100 mL of benzene in an ice bath. The first portion of the iodine was rapidly decolorized,but the color soon persisted. The flask was allowed to warm to room temperature and stirring continued for 2 days. The unchanged iodine was then destroyed by washing the benzene solution with aqueous sodium bisulfite. The pale yellow benzene layer was washed with saturated sodium chloride solution. Evaporation of the benzene at reduced pressure gave a reddish semisolid,which was extracted with hot n-hexane. The crude material was recrystallized fromn-hexane-chloroform to give pure products 3a-3c.

3,3,5,5-Tetrabenzyl-1,2,4-trithiole (3a): White solid,yield 83%, mp 144-146℃;¹H NMR (400 MHz,DMSO-d₆):δ 2.79(s,8H,CH₂), 7.31-7.37 (m,12H,Ar-H),7.43-7.48 (m,8H,Ar-H); IR (KBr,cm^-1): υ 3032,2917,1611,1593; EI-MS (m/z): 91 (100%),484 (M⁺,4.29%). Anal. Calcd. for C₃₀H₂₈S₃: C 73.38,H 5.79; Found: C 73.52,H 5.71.

3,3,5,5-Tetra(4-bromobenzyl)-1,2,4-trithiole (3b): White solid, yield 77%,mp 173-175℃;¹H NMR (400 MHz,DMSO-d₆):δ 2.80 (s, 8H,CH₂),7.33-7.37 (m,8H,Ar-H),7.59-7.64 (m,8H,Ar-H); IR (KBr,cm^-1): υ 3025,2917,1607,1591; EI-MS (m/z): 169 (100%),796 (M⁺,1.45%). Anal. Calcd. for C₃₀H₂₄Br₄S₃: C 45.23,H 3.02; Found: C 45.37,H 3.11.

3,3,5,5-Tetra(4-nitrobenzyl)-1,2,4-trithiole (3c): White solid, yield 73%,mp 201-203℃;¹H NMR (400 MHz,DMSO-d₆):δ 2.90 (s, 8H,CH₂),7.37-7.40 (m,8H,Ar-H),8.21-8.25 (m,8H,Ar-H); (KBr, cm^-1): υ 3047,2911,1611,1597; EI-MS (m/z): 136 (100%),664 (M⁺,3.46%). Anal. Calcd. for C₃₀H₂₄N₄O₈S₃: C 54.22,H 3.61,N 8.43; Found: C 54.41,H 3.54,N 8.59.

A solution of 1,3-diarylpropane-2,2-dithiol (0.01 mol) in 50 mL of absolute alcohol was saturated with hydrogen chloride at 0- 5℃,and the mixture was stirred at 78℃. After 1.5 h,the flask was stored in a refrigerator overnight and a white solid appeared. The crude product was recrystallized from ethanol to give pure products 4a-4c.

An alcohol solution of compound 4a was allowed to stand at room temperature and the alcohol was allowed to slowly evaporate. White crystals suitable for X-ray diffraction analysis were isolated one week later.

1,2-Dis(1,3-diphenylpropan-2-yl)disulfane (4a): white solid, yield 90%,mp 126-128℃;¹H NMR (400 MHz,DMSO-d₆):δ 2.75 (d,J= 7.2 Hz,8H,CH₂),3.28-3.31 (m,2H,CH),7.26-7.29 (m,12H,ArH),7.41-7.45 (m,8H,Ar-H); IR (KBr,cm^-1):υ 3019,2917,1593; EIMS (m/z): 91 (100%),454 (M⁺ ,3.19%). Anal. Calcd. for C₃₀H₃₀S₂:C 79.30; H 6.61. Found: C 79.58,H 6.43.

1,2-Dis[1,3-di(4-bromophenylpropan)-2-yl]disulfane (4b): White solid,yield 81%,mp 143-145℃;¹H NMR(400MHz,DMSO-d₆):δ 2.76(d,J= 7.2 Hz,8H,CH₂),3.27-3.29 (m,2H,CH),7.31-7.34 (m,8H,Ar-H), 7.57-7.61 (m,8H,Ar-H); IR (KBr,cm^-1 ):υ 3021,2911,1597; EI-MS (m/z): 169 (100%),766 (M⁺ ,1.02%).Anal.Calcd.for C₃₀H₂₆Br₄S₂: C 47.00,H 3.39; Found: C 47.12,H 3.47.

1,2-Dis[1,3-di(4-nitrophenylpropan)-2-yl]disulfane (4c): White solid,yield 83%,mp 197-199℃;1 HNMR(400MHz,DMSO-d₆):δ 2.91 (d,J= 7.2 Hz,8H,CH₂),3.35 (m,2H,CH),7.38 (m,8H,ArH),8.19 (m,8H,Ar-H); (KBr,cm^-1):υ 3021,2907,1599; EI-MS (m/z): 136 (100%),634 (M⁺ ,5.71%). Anal. Calcd. for C₃₀H₂₆N₄O₈S₂: C 56.78,H 4.10,N 8.83; Found: C 56.93,H 4.02,N 8.76.

The synthesis of compound 2 followed literature procedures ^[6] and the isolated yield was in agreement with the literature report.

The ¹H NMR,IR and elemental analysis data of these products supported their proposed chemical structures. A white single crystal of compound 4a with dimensions of 0.16 mm×0.15 mm×0.10 mm was chosen for X-ray diffraction analysis performed on a BRUCKER SMART APEX-CCD diffractometer equipped with a graphite-monochromatic Mo Kα radiation (λ= 0.71073 Å ) radiation at 298(2) K. A total of 5119 reflections were collected in the range of 1.96°<u<30.00° by using a ψ-ω scan mode with 3278 independent ones (R_int = 0.0464),in which 3211 with I>2σ(I) were observed and were used in the subsequent refinements. The data set was corrected by SADABS program,the structure was solved by direct methods and expanded by Difference Fourier techniques with SHELXS-97 ^[7]. The non-hydrogen atoms were refined anisotropically and the hydrogen atoms were added according to the theoretical models.The structure was refined by the full-matrix least-squares method on F² with SHELXL-97 ^[8]. The final refinement gave R= 0.0490, wR= 0.1247 (w= l/[σ²(F_o²)+(0.0682P)²+1.7325P],where P=(F_O²+2FC²)/3,S= 1.059,(Δ/σ)_max= 0.001,(Δρ)_max= 2.403 and (Δρ) _min =0.296/ų.

Fig. 1

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Fig. 1. Molecular structure of compound 4a.

Fig. 2

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Fig. 2. Packing diagram of compound 4a.

The molecular structure and packing diagram are depicted in Figs. 1 and 2,respectively. In the crystal structure,the bond length (1.834(2)) of C(8)-S(1) is longer than that (1.533(3)) of C(7)-C(8) and the bond length of S(1)-S(1a)(2.0284(9)) is the longest. Moreover,there is no center of symmetry and symmetry plane in the molecule. So the molecule is not symmetrical. In the aromatic rings in the molecule,the molecular dimensions are as expected with the aromatic C-C bond distances between 1.388(4) and 1.408(4) Å ,and these bond lengths are even. The aromatic C-C-C bond angles ranging from 118.1(2) to 121.14(18)8 are almost within the normal ranges ^[9]. Each of the rings is nearly planar. It can be seen that the molecular structure is stabilized by weak π-π stacking interactions and there no classical hydrogen bonds can be observed.

In conclusion,a series of novel sulfur-containing compounds were synthesized in ethanol using 1,3-diphenyl-2-propanone as the starting material. The advantages of this procedure include mild reaction conditions,simple protocols,and high yields. The crystal structure of the new compound 4a was obtained. Other properties of these compounds are being studied.

We are grateful for the Natural Science Foundation of Hubei Province (No. 2012FFB01103),the Hubei Provincial Department of Education (No. Q20131905),the National Natural Science Foundation of China (No. 21262011),and the Fund of Ethnic Affairs Commission of China (No. 12HBZ010).