Molecules 2014, 19
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2,6-Di-tert-butyl-4-(5-(3,5-dichlorophenyl)-1,3,4-oxadiazol-2-yl)phenol (5h). The crude product was
purified by recrystallized from acetonitrile to afford a white amorphous solid. Yield 0.386 g (74%),
m.p. 195–197 °C, IR (KBr, νmax/cm−1): 3600 (OHphenol), 3007 (CHaromatic), 2961 (CHaliphatic), 1606 (C=N),
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1574, 1550 (C=C), 1240 (C-O), H-NMR (CDCl3, 400 MHz, ppm): 1.52 (s, 18H, H14, 2 × t-Bu),
5.69 (s, 1H, OH), 7.51 (t, 1H, J = 1.24 Hz, H10), 7.93 (s, 2H, H3), 8.01 (t, 2H, J = 1.72 Hz, H8 & H12),
13C-NMR (CDCl3, 100 MHz, ppm): 30.39 (6C, C14, 2 × C(CH3)3), 34.50 (2C, C13, 2 × C(CH3)3),
114.73 (C4), 124.48 (C3), 125.02 (2C, C8 & C12), 126.87 (C7), 131.24 (C10), 135.92 (C9 & C11),
136.93 (C2), 157.50 (C1), 161.877 (C5), 166.05 (C6). HREIMs m/z = 418.1210 [M•+] (calc. for
C22H24O2N2Cl2, 418.1215).
2,6-Di-tert-butyl-4-(5-(2,4-dimethylphenyl)-1,3,4-oxadiazol-2-yl)phenol (5i). The crude product was purified
by recrystallized from toluene to give white crystalline needles. Yield 0.28 g (60%), m.p. 170–172 °C.
IR (KBr, νmax/cm−1): 3587 (OHphenol), 2957 (CHaliphatic), 1614 (C=N), 1550, 1536 (C=C), 1238 (C-O),
1H-NMR (CDCl3, 400 MHz, ppm): 1.50 (s, 18H, H14, 2 × t-Bu), 2.39 (s, 3H, H15), 2.70 (s, 3H, H16),
5.64 (s, 1H, OH), 7.17–7.14 (m, 2H, H9 & H11), 7.95–7.90 (m, 3H, H12, H3'), 13C-NMR (CDCl3, 100 MHz,
ppm): 21.50 (C16, o-CH3), 22.04 (C15, p-CH3), 30.22 (6C, C14, 2 × C(CH3)3), 34.55 (2C, C13, 2 × C(CH3)3),
115.40 (C4), 12.60 (C7), 124.38 (C3), 126.98 (C11), 128.96 (C12), 132.59 (C9), 136.79 (C2), 138.19 (C8),
141.43 (C10), 157.11 (C1), 164.49 & 164.81 (C5 & C6). HREIMs m/z =378.2301 [M•+] (calc. for
C24H30O2N2, 378.2307).
2,6-Di-tert-butyl-4-[5-(2-methylphenyl)-1,3,4-oxadiazol-2-yl] phenol (5j). The product was recrystallized
from ethyl acetate to afford white crystals, 0.308 g (68.5%), m.p. 132–134 °C, IR (KBr, νmax/cm−1):
3588 (OHphenol), 3008 (CHaromatic), 2963 (CHaliphatic), 1607 (C=N), 1592, 1537 (C=C), 1238 (C-O),
1H-NMR (CDCl3,400 MHz, ppm): 1.52 (s, 18H, H14, 2 × t-Bu), 5.66 (s, 1H, OH), 7.44–7.34 (m, 3H,
H9, H10, H11), 7.96 (s, 2H, H3, H3'), 8.02 (d, 1H, J = 7.32 Hz, H12), 13C-NMR (CDCl3, 100 MHz, ppm):
2 2.11 (o-CH3), 30.22 (6C, C14, 2 × C(CH3)3), 34.52 (2C, C13, 2 × C(CH3)3), 115.53 (C4), 123.40 (C7),
124.37 (C3), 126.21 (C11), 128.96 (C12), 131.03 (C10), 131.80 (C9), 136.80 (C2), 138.35 (C8), 157.14 (C1),
164.32 & 165.04 (C5 & C6), HREIMs m/z = 364.2144 [M•+] (calc. for C23H28O2N2, 364.2151).
2,6-Di-tert-butyl-4-(5-(2-chlorophenyl)-1,3,4-oxadiazol-2-yl)phenol (5k). The crude product was
recrystallized from ethyl acetate to obtain white crystals. Yield 0.386 g (81%), m.p. 113–115 °C,
IR (KBr, νmax/cm−1): 3584 (OHphenol), 3004 (CHaromatic), 2959 (CHaliphatic), 1607 (C=N), 1570, 1539 (C=C),
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1239 (C-O), H-NMR (CDCl3, 400 MHz, ppm): 1.48(s, 18H, H14, 2 × t-Bu), 5.66 (s, 1H, OH),
7.38–7.46 (m, 2H, H10, H11), 7.53 (d, 1H, J = 8.04 Hz, H12), 7.95 (s, 2H, H3, H3'), 8.05 (d, 1H, J = 6.32 Hz,
H9), 13C-NMR (CDCl3, 100 MHz, ppm): 30.27 (6C, C14, 2 × C(CH3)3), 34.61 (2C, C13, 2 × C(CH3)3),
115.18 (C4), 123.65 (C7), 124.61 (C3), 127.21 (C11), 131.33 (C12), 132.32 (C9), 133.14 (C8),
136.79 (C9), 136.94 (C2), 157.28 (C1), 162.55 & 166.04 (C5 & C6). HREIMs m/z = 384.1600 [M•+]
(calc. for C22H25O2N2Cl, 384.1605).
5. Conclusions
A series of new 1,3,4-oxadiazole compound incorporating hindered phenol moities were successfully
synthesized and characterized. All of the new compounds were screened for antioxidant activity using