General
Uncorrected Melting points were taken in a Gallenkamp melting point apparatus (Weiss-Gallenkamp, Loughborough, UK). The infrared spectrum of I was determined with a Bruker Alpha ATR instrument. The NMR spectra of I were measured in CDCl3 and were recorded on a Bruker Avance 400 NMR instrument at 400 MHz for 1H NMR and 100 MHz for 13C NMR. For the characterization of centrosymmetric signals, the signal's median point was chosen; for multiplets, the signal range was given. The following abbreviations were used to describe the proton splitting pattern: d = doublet, t = triplet, m = multiplet, dd = doublet of a doublet. Mass spectra were observed by FAB (Fast atom bombardment) experiments and were recorded using a Finnigan MAT 90 (70 eV) instrument. Elemental analyses were performed on an Elementar vario MICRO instrument. TLC silica plates coated with fluorescence indicator from Merck (silica gel 60 PF254, thickness 0.2 mm) were used to identified the products.
Synthesis of 4,4'-thio-bis(1-methylquinoline-2(1 H )-thione (I)
A mixture of 4-chloro-1-methylquinolin-2(1H)-one (1) (0.193 g, 1 mmol) and P4S10 (0.193 g, 1 mmol) was heated at 100 oC in 30 ml pyridine for 2 h (the reaction was followed up by TLC analysis). The reaction mixture was poured into ice water and the formed precipitate was filtered and recrystallized from CHCl3. The solution of recrystallization was left 2 d until the monoclinic brown crystals were formed.
Color; brown crystals; m.p. 310°C, yield; 55%; IR (KBr): νmax/cm− 1 = 3066 (Ar-CH), 2934 (Aliph-CH), 1662 and 977 (C = S), 1628 (C = N). 1H NMR (400 MHz, CDCl3, ppm) δH = 8.01 (dd, J = 8.1, 1.3 Hz, 2H, Ar-H), 7.76–7.67 (m, 2H, Ar-H), 7.64 (d, J = 8.6 Hz, 2H, Ar-H), 7.58 (s, 2H, Ar-H), 7.41–7.35 (m, 2H, Ar-H), 4.31 (s, 6H, 2CH3). 13C NMR (100 MHz, CDCl3, ppm) δ = 182.8 (2C = S), 164.2 (2C-S), 140.8 (2C-Ar), 136.9 (2C-Ar), 135.8 (2CH-Ar), 132.2 (2CH-Ar), 126.0 (2CH-Ar), 124.5 (2CH-Ar), 116.4 (2CH-Ar), 38.1 (2CH3). MS (FAB, 3-NBA), m/z (%): 380 (100) [M]+, 347 (43), 207 (43). Anal. for C20H16N2S3 (380): Calcd. C, 63.13; H, 4.24; N, 7.36. Found: C, 63.19; H, 4.31; N, 7.42.
Synthesis of 3,3'-methylenebis(4-hydroxy-1-methylquinolin-2(1 H )-one) (II)
Compound II was prepared according to the literature [18]. Compound II was recrystallized from DMF. The solution was left for 3 d until the growth of hexagonal yellow crystals.
X-ray structure analyses of compounds I and II
Single crystal X-ray diffraction data of compounds I and II were collected on an STOE STADI VARI diffractometer with monochromated Ga Kα (1.34143 Å) radiation at low temperatures. Using Olex2 [23], the structures were solved with the ShelXT [24] structure solution program using Intrinsic Phasing and refined with the ShelXL [25] refinement package using Least Squares minimization. Refinement was performed with anisotropic temperature factors for all non-hydrogen atoms; hydrogen atoms were calculated on idealized positions.
Crystallographic data for compounds I and II reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary information no. CCDC-2236514 and 2236515. Copies of the data can be obtained free of charge from
https://www.ccdc.cam.ac.uk/structures/ .