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characterized using a Holland Philips Xpert X-ray diffraction (s, 3H, CH3), 6.95 (s, 1H, thiazole), 7.02 (s, 2H, NH2), 7.05 (d, J ¼
(XRD) diffractometer (CuK, radiation, l ¼ 0.154056 nm), at 7.8 Hz, 1H, Ar-H), 7.22 (t, 1H, J ¼ 7.9 Hz, Ar-H), 7.56 (d, J ¼ 7.9
a scanning speed of 2ꢁ minꢀ1 from 10ꢁ to 100ꢁ (2q). The surface Hz, 1H, Ar-H), 7.60 (s, 1H, Ar-H).
morphology of samples was characterized by scanning electron
3.4.6. 4-(2-Hydroxyphenyl)thiazol-2-amine. Yellow powder;
microscopy (SEM; EM3200) and transmission electron micros- mp ¼ 138–139; yield: 163 mg (85%); IR (KBr): 3246, 2064, 1635,
copy (TEM; Philips CM10).
1569, 1461, 743 (cmꢀ1); 1H NMR (400 MHz, DMSO-d6): d ¼ 6.88
(t, 1H, J ¼ 7.6 Hz, 1H, ArH), 6.89 (d, J ¼ 8.24 Hz, 1H, ArH), 7.16
(s, 1H, thiazole, D2O exchangeable), 7.24 (t, J ¼ 8.24 Hz, 1H,
ArH), 7.52 (d, J ¼ 7.6 Hz, 1H, ArH), 8.70 (s, 1H, OH, D2O
exchangeable).
3.2. Procedure for preparation of Fe3O4 NPs
Typically, 10 mmol of FeCl3$6H2O and 5 mmol of FeCl2$4H2O
were dissolved in 35 mL of distilled water in a round bottom
ask (250 mL) under Ar atmosphere for 1 h. In the next step, 5
mL of NaOH (10 M) was added into the solution within 30 min
with vigorous mechanical stirring. Aer one hour, the resultant
black dispersion was heated to 85 ꢁC for 1 h. The black
precipitate formed was isolated by magnetic decantation,
exhaustively washed with double-distilled water until neutrality,
and further washed twice with ethanol and dried at 60 ꢁC in
vacuum19.
3.4.7. 4-(4-Hydroxyphenyl)thiazol-2-amine. Yellow powder;
mp ¼ 198–200; yield: 174 mg (91%) IR (KBr): 3447, 2921, 1610,
1504, 1435, 834 (cmꢀ1); 1H NMR (400 MHz, DMSO-d6): d ¼ 6.69
(d, J ¼ 8.5 Hz, 2H, Ar-H), 6.70 (s, 1H, thiazole), 6.95 (d, 2H, NH2),
7.58 (d, J ¼ 8.5 Hz, 2H, Ar-H), 9.50 (s, OH).
3.4.8. 4-Methyl-5(ethoxycarbonyl)thiazol-2-amine. White
powder, mp ¼ 177–179; yield: 182 mg (98%); IR (KBr): 3374,
3085, 1674, 1515, 1373, 756 (cmꢀ1); 1H NMR (400 MHz, DMSO-
d6): d ¼ 1.21 (t, J ¼ 7.1, 3H, CH3), 2.48 (s, 3H, CH3), 4.12 (q, 2H,
CH2), 7.71 (S, 2H, NH2).
3.3. General procedure for the synthesis of 2-aminothiazoles
3.4.9. 4-Methyl-5(methoxycarbonyl)thiazol-2-amine. White
powder; mp ¼ 225–226; yield: 170 mg (99%); IR (KBr): 3374,
A mixture of methylcarbonyl (0.5 equiv.), DCDMH (0.5 equiv.)
and Fe3O4 NPs in CH3OH (2 mL) at 65 C was stirred for 1 h.
ꢁ
1
3085, 1682, 1644, 1504, 1320, 758 (cmꢀ1); H NMR (400 MHz,
Then thiourea (0.5 equiv.) was added to the mixture and was
stirred for 1 h. Aer the completion of reaction, reaction
mixture was ltered off and the ltrate was washed by sodium
bicarbonate solution and brine and extracted with ethyl acetate.
The organic layer was separated followed by drying using
anhydrous sodium sulfate and concentrated under reduced
pressure to afford the precipitate. The solid obtained was crys-
tallized from a mixture of water and ethanol.
DMSO-d6): d ¼ 2.57 (s, 3H, CH3), 3.85 (s, 3H, CH3), 6.12 (S, 2H,
NH2).
3.4.10. 4-Methyl-5(allyloxycarbonyl)thiazol-2-amine. White
powder; mp ¼ 148–149; yield: 194 mg (98%); IR (KBr): 3375,
3083, 1672, 1514, 1374, 754 (cmꢀ1); 1H NMR (400 MHz, DMSO-
d6): d ¼ 2.38 (s, 3H, CH3), 4.15 (d, J ¼ 5.4 Hz, 2H, CH2), 5.26 (d,
1H, CH), 7.30 (d, 1H, CH), 5.92 (m, 1H, CH), 7.52 (s, 2H, NH2).
4. Conclusions
3.4. Spectroscopic data of representative products
3.4.1. Thiazole-2-amine. Pale yellow powder; mp ¼ 89–90; In summary, we have demonstrated an efficient, simple, effi-
yield: 98 mg (98%); IR (KBr): 3410, 3289, 3084, 1629, 1521, 1491, cient and sable catalyst-N-halo reagent for the synthesis of 2-
1
698 (cmꢀ1); H NMR (400 MHz, DMSO-d6): d ¼ 6.52 (d, J ¼ 3.7 amintothiazole. We compared DCDMH, NBS, and NIS as N-halo
Hz, 1H), 6.75 (s, 2H, NH2, D2O exchangeable), 6.90 (d, J ¼ 3.7 Hz, reagent for the synthesis of 2-aminothiazole and observed that
1H).
DCDMH showed best results. This method is quick, and avoids
3.4.2. 4-Phenylthiazol-2-amine. Yellow crystal, mp ¼ 151– the use of toxic or heavy metal, high temperature, and leads to
153; yield: 163 mg (93%); IR (KBr): 3424, 3256, 2856, 1623, 1519, improved product yields and easy work-up procedure.
1336, 728 (cmꢀ1); 1H NMR (400 MHz, DMSO-d6): d ¼ 6.92 (s, 1H,
thiazole), 7.22 (s, 2H, NH2, D2O exchangeable), 7.32 (t, J ¼ 7.9
Acknowledgements
Hz, 1H, Ar-H), 7.69 (t, J ¼ 7.9 Hz, 2H, Ar-H), 7.71 (m, J ¼ 7.05 Hz,
2H, Ar-H).
This study is part of Masoud Sadeghi PhD thesis entitled: “The
3.4.3. 5-Acetyl-4-methybhiazole-2-amin. White crystal; mp presentation of new nanocatalytic and non-catalytic methods
¼ 215–217; yield: 154 mg (99%); IR (KBr): 3350, 2920, 1680 for the synthesis of 2-aminothiazole derivatives from methyl-
1
(cmꢀ1); H NMR (400 MHz, DMSO-d6): d ¼ 2.21–2.29 (2s, 6H, carbonyls” which has been conducted in the University of
2CH3). 5.32 (s, 2H, NH2).
Kashan. We gratefully acknowledge the nancial support from
3.4.4. 4-(4-Chlorophenyl)thiazol-2-amine. White crystal; the Research Council of the University of Kashan for supporting
mp ¼ 160–162; yield: 186 mg (89%); IR (KBr): 3426, 2924, 1628, this work by Grant No. 363022/12.
1570, 1495, 744 (cmꢀ1); 1H NMR (400 MHz, DMSO-d6): d ¼ 7.24
(s, 1H, thiazole, D2O exchangeable), 7.55 (d, J ¼ 8.4 Hz, 2H, Ar-
References
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3.4.5. 4-(3-Methylphenyl)thiazol-2-amine. Yellow powder,
mp ¼ 88–91, yield; 167 mg (88%); IR (KBr): 3425, 2919, 1605,
1521, 1468, 714 (cmꢀ1); 1H NMR (400 MHz, DMSO-d6): d ¼ 2.48
64754 | RSC Adv., 2016, 6, 64749–64755
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