1
730
TANDON AND CHHOR
Perkin-Elmer model R-32 spectrometer in CDCl using TMS as internal
3
stan da rdandMass spectra on a Joel-JMS-D-300 spectrometer. Spectral
facilities andelemental micro-analysis were carriedout by R.S.I.C. of
Central Drug Research Institute, Lucknow. Analysis of C, H, N was found
within difference of ꢂ0.4%.
General Procedure for Synthesis of 1,3,4-oxadiazoles: To a stirredsol-
ution of acid chloride or aroyl chloride (0.01 mole) in dry dioxane (50 ml)
ꢁ
was added hydrazine hydrate (0.005 mole) at 0 C andstirredfurther for
3
added dropwise to the above stirred reaction mixture in 15 min and reaction
0 min at room temp. BF ꢀEt O (0.025 mole) in dry dioxame (5 ml) was
3
2
ꢁ
mixture further refluxedfor 1 to 2 h at 130 C. The resulting solution was
ꢁ
concentratedin vacuo, saturatedNH Cl solution added at 0 C till the pH
4
becomes 6, ectractedwith EtOAc, dr iedover Na SO andconcentratedin
2
4
vacuo to give the crude product, which was further purified by column
chromatography [SiO -(MeOH-CHCl , 1:4)] to give 1,3,4-oxadiazoles
2
3
(
91–98%).
2
1
6a
ꢃ1
,
,5-Diphenyl-1,3,4-oxadiazole (2a) : ꢀmax 968, 1024, 1548, 1639 cm
þ
dH 7.26–8.19 (m, 10H, Ar-H), M , 222 (m/z), 165.
ꢃ1
2
,5-Dimethyl-1,3,4-oxadiazole (2b): ꢀ
1024, 1460, 1602 cm , dH
max
þ
1
.18 (s, 6H, 2 Â CH ), M , 98 (m/z).
3
ꢃ1
þ
2
,5-Dimethyl-1,3,4-oxadiazole (2c): ꢀ
929, 1022, 1531, 1678 cm
,
max
dH 0.98 (t, J ¼ 4 Hz, 6H, 2 Â CH ), 2.2 (q, J ¼ 4Hz, 4H, 2 Â CH ), M ,
3
2
1
26 (m/z).
2
ꢃ1
,5-Di(3-chlorophenyl)-1,3,4-oxadiazole(2d):ꢀmax1074,1569,1695cm
,
þ
dH 7.30–7.60 (m, 6H, Ar-H), 7.89–7.92 (m, 2H, Ar-H), M , 293 (m/zþ2),
2
91 (m/z), 289 (m/z-2).
2
1
6b
,5-Di-(4-aminophenyl)-1,3,4-oxadiazole (2e) : ꢀmax 1033, 1406,
ꢃ1
1
645 cm , dH 6.61–6.66 (m, 4H, m to ArNH ), 7.85–7.87 (m, 4H, 0 to
2
þ
ArNH ), 7.16 (s, 4H, 2 Â NH ), M , 252 (m/z).
2
2
2
,5-Di-(2-hydroxyphenyl)-1,3,4-oxadiazole (2f): ꢀmax 1033, 1556,
ꢃ1
3
(
093 cm , dH 6.97 (d, J ¼ 8 Hz, 2H, ArH), 7.44–7.51 (m, 4H, ArH), 7.94
þ
d, J ¼ 8H, 2H, ArH), 10.91 (s, 1H, OH), M , 254 (m/z).
2
,5-Di-(4-fluorophenyl)-1,3,4-oxadiazole (2g): ꢀ
929, 1014, 1550,
þ
max
ꢃ1
1
602 cm , dH 6.99–7.15 (m, 4H, ArH), 7.96–8.16 (m, 4H, ArH), M ,
2
58 (m/z).
2
ꢃ1
,5-Dicyclohexyl-1,3,4-oxadiazole (2h): ꢀ
956, 1033, 1550, 1670 cm
,
max
þ
dH 1.17–2.38 (m, 22H, cyclohexyl), M , 234 (m/z).
2
,5-Di(3-nitrophenyl)-1,3,4-oxadiazole (2i): ꢀ
914, 1082, 1352, 1583,
max
ꢃ1
þ
1
618 cm , dH 7.58-8.61 (m, 8H, ArH), M , 312 (m/z).
,5-Dibenzamidomethyl-1,3,4-oxadiazole (2j): ꢀmax 929, 1055, 1593,
2
1
2
631, 1737; dH 2.50 (s, 4H, 2CH ), 8.24–8.89 (m, 10H, ArH), 9.28 (s, 2H,
NH), M , 336 (m/z).
2
þ