138
K.K. Bhasin et al. / Journal of Organometallic Chemistry 732 (2013) 137e141
2.3. Synthesis of 4,6-dimethyl-2-chloropyrimidine [26]
DMF
4E + N2H4.H2O + 4 NaOH
2Na2E2 + 5 H2O + N2
A mixture of 4,6-dimethyl-2-hydroxypyrimidine hydrochloride
(20.0 g, 0.125 mol) and phosphorous oxychloride (110 ml) was
refluxed for 10 h after which time the residual phosphorous oxy-
chloride was removed in vacuum. The residual oil was poured into
50 g of ice and was neutralized below 10 ꢁC with a concentrated
solution of potassium hydroxide. The resulting mixture with
300 ml diethyl ether was vigorously stirred for 10 h. The organic
extract was evaporated to dryness. The residual crude product was
recrystallized from a minimal amount of petroleum ether (b.pt. 40e
CH3
CH3
CH3
N
N
DMF
N
2-
E2
+
H3C
N
E
E
N
CH3
H3C
N
Cl
Ia-c
E = S, Se, Te
Scheme 1. Scheme for the synthesis of bis(4,6-dimethyl-2-pyrimidyl)dichalcogenides,
Iaec.
70 ꢁC) giving 13.8
chloropyrimidine plates (m.pt. 37e38 ꢁC). 1H NMR (CDCl3/CCl4)
6.89(1H, s), 2.37 (6H, s).
g (77%) of as colorless 4,6-dimethyl-2-
under vacuum. The organic layer was repeatedly washed with
distilled water (3 ꢂ 40 ml), dried over anhydrous sodium sulfate.
Solvent was removed on a rota evaporator and the product was
subjected to purification on a silica column using hexane as eluant.
d
2.4. Synthesis of bis(4,6-dimethyl-2-pyrimidyl)dichalcogenide
(Iaec)
2.5.1. 4,6-Dimethyl-2-(phenylselanyl)pyrimidine (IIa)
To a vigorously stirred mixture of powdered sodium hydroxide
(3.0 g, 75 mmol), elemental chalcogen (S ¼ 1.6 g, 50 mmol,
Se ¼ 4.0 g, 50 mmol or Te ¼ 6.4 g, 50 mmol) and dimethylforma-
mide (30 ml), 100% hydrazine hydrate was added slowly. After
stirring for nearly 6 h at room temperature, a solution of 4,6-
dimethyl-2-chloropyrimidine (100 mmol) dissolved in 15 ml DMF
was added drop wise. The reaction mixture was refluxed for 2e3 h
and continuously monitored by TLC. After the completion of the
reaction, it is diluted with about 250 ml of distilled water and
extracted with dichloromethane (3 ꢂ 50 ml). The organic layer was
separated and solvent removed to get the crude product in solid
form. The product was subjected to purification on a silica column
using hexane as the eluant.
Yield ¼ 75%, white crystalline solid, m.p. ¼ 58e62 ꢁC, Anal. Calc
for C12H12N2Se: Calcd. C, 54.50; H, 4.54, N, 10.60. Found: C, 54.89, H,
4.35, N, 10.86. IR (KBr, cmꢀ1): 2924.0, 1578.0, 1529.0, 1438.0, 1341.0,
783.0, 542.0. 1H NMR:
d
7.63e7.60 (2H, d), 7.26e7.24 (3H, m), 6.58
170.3,166.9,136.9,136.0,129.6,128.2,
(1H, s), 2.28 (6H, s); 13C NMR:
d
117.5, 36.8, 23.8; 77Se NMR:
d
486.8; MS-EI, m/e (R.I. %, assignment):
265 (100, [C12H12N2Se]þ þ 1), 185 (30, [C6H7N2Se]þ ꢀ 2).
ꢃ
2.5.2. 4,6-Dimethyl-2-(naphthalen-2-ylselanyl)pyrimidine (IIb)
Yield ¼ 67%, yellow crystalline solid, m.p. ¼ 95e97 ꢁC, Calcd.
Anal. Calc for C16H14N2Se: C, 61.14 H, 4.45, N, 8.91. Found: C, 61.01, H,
4.22, N, 8.65. IR (KBr, cmꢀ1): 2925.1, 1541.5, 1399.1, 1324.1, 791.0,
669.4. 1H NMR:
d
7.80e7.78 (1H, d), 7.44e7.35 (3H, d), 7.18e7.11 (2H,
t), 6.86 (1H, s), 6.60 (1H, d), 2.41 (6H, s); 13C NMR:
d
175.1, 160.6,
2.4.1. Bis(4,6-dimethyl-2-pyrimidyl)disulfide (Ia)
157.2, 137.4, 134.6, 134.5, 131.8, 128.9, 128.1, 127.6, 124.3, 118.7, 23.8.
Yield ¼ 60%, white crystalline solid, m.p. ¼ 115e116 ꢁC, Anal.
Calc for C12H14N4S2: Calcd. C, 51.79, H, 5.03, N, 20.14. Found: C, 51.57,
H, 5.23, N, 20.40. IR (KBr, cmꢀ1): 2919.0, 1659.9, 1376.5, 1455.0,
2.5.3. 2-(p-tolylselanyl)-4,6-dimethylpyrimidine (IIc)
Yield ¼ 78%, light yellow crystalline solid, m.p. ¼ 67e69 ꢁC, Anal.
Calc for C13H14N2Se: Calcd. C, 56.11, H, 5.03, N, 10.07. Found: C,
55.99, H, 5.23, N, 10.23. IR (KBr, cmꢀ1): 2926.4, 1570.0, 1524.0,
881.5, 842.4, 766.2, 722.2. 1H NMR:
d C
6.64 (1H, s), 2.36 (6 H, s); 13
NMR: d 169.4, 167.2,116.8, 23.9; MS-EI, m/e (R.I. %, assignment): 279
(100, [C12H14N4S2þ1]þꢃ), 245 (10, [C12H14N4S ꢀ 1]þꢃ), 140 (5,
1421.0, 783.0, 542.0. 1H NMR:
d
7.58e7.52 (2H, d), 6.86e6.81 (2H, d),
[C6H7N2S þ 1]þꢃ).
6.63 (1H, s), 3.81 (3H, s), 2.29 (6H, s); 13C NMR:
d
170.5, 166.9, 159.9,
137.7, 118.5, 117.4, 116.6, 115.6, 114.5, 113.6, 55.7, 23.8; MS-EI, m/e
2.4.2. Bis(4,6-dimethyl-2-pyrimidyl)diselenide (Ib)
(R.I. %, assignment): 278 (100, [C13H14N2Se]þꢃ).
Yield ¼ 58%, red crystalline solid, m.p. ¼ 142e145 ꢁC, Anal. Calc
for C12H14N4Se2: Calcd. C, 38.50, H, 3.94, N, 14.97.Found: C, 38.17, H,
3.72, N, 14.71. IR (KBr, cmꢀ1): 2923.3, 2852.5, 1580.0, 1384.0, 785.9.
2.5.4. 2-(4-Chloropyrimidin-2-ylselanyl)-4,6-dimethylpyrimidine
(IId)
1H NMR:
d d 168.9, 167.3, 116.9,
6.60 (1H, s), 2.30 (6H, s); 13C NMR:
Yield ¼ 54%, white crystalline solid, m.p. ¼148e149 ꢁC, Anal. Calc
for C10H9N4SeCl: Calcd. C, 39.93, H, 2.99, N,18.63. Found: C, 40.20, H,
3.13, N, 18.37. IR (KBr, cmꢀ1): 2925.4, 1581.7, 1543.2, 1398.5, 1328.9,
23.8; 77Se NMR:
d
486.2; MS-EI, m/e (R.I. %, assignment): 371 (þ32,
[C12H14N4Se2]þ ꢀ 3), 213(95, [C12H14N4]þ ꢀ 1) 107(96, [C6H7N2] ꢃ).
ꢃ
ꢃ
844.3, and 540.5. 1H NMR:
d 8.39e8.36 (1H, d), 8.36e8.33 (1H, d),
2.4.3. Bis(4,6-dimethyl-2-pyrimidyl)ditelluride (Ic)
6.79 (1H, s), 2.39 (6H, s); 13C NMR:
d 167.7, 157.3, 122.1, 118.2, 23.8.
Yield ¼ 50%, blue crystalline solid, m.p. ¼ 121e124 ꢁC, Anal. Calc
for C12H14N4Te2: Calcd. C, 30.63, H, 2.97, N, 11.91. Found: C, 30.50, H,
2.88, N,11.55. IR (KBr, cmꢀ1): 2929.8, 2838.5,1600.0,1369.0, 706.3.1H
2.6. X-ray crystallographic studies
NMR: d d 169.0,165.0,117.4, 23.81.
6.51 (1H, s), 2.25 (6H, s); 13C NMR:
Diffraction quality colorless single crystals of Ib and IIa were ob-
tainedby the slow evaporation of dichloromethaneehexane solution
2.5. Synthesis of 4,6-dimethyl-2-(arylselanyl)pyrimidine
compounds (IIaed)
CH3
NaBH4/C2H5OH-DMF,0-50C
N
Ar-Se-Se-Ar
To a solution of diaryldiselenide, Ar2Se2 (Ar ¼ phenyl, naphthyl,
tolyl, 4-chloro-2-pyrimidyl) in 50 ml of C2H5OH-DMF (3:2) was
added 0.456 g (12 mmol) of sodium borohydride in parts with
continuous stirring at 0e5 ꢁC. To the resulting solution, 10 mmol of
4,6-dimethyl-2-chloropyrimidine diluted with an equal volume of
DMF was added drop wise. Reaction was complete within 1e2 h.
Extraction was done in dichloromethane after removing ethanol
CH3
H3C
N
Se Ar
II a-d
Ar = C6H5, C10H7, p-CH3C6H5, , C4N2H2Cl.
Scheme 2. Scheme for the synthesis of 4,6-dimethyl-2-(arylselanyl)pyrimidines, IIaed.
r.t
N
,
N
H3C
Cl