J. Chil. Chem. Soc., 55, Nº 1 (2010)
The dibenzyl bromide (2a:R=Me, 2b:R=Ph) derivatives were synthesized
according to a procedure described previously.5,6 This reaction uses benzoyl
peroxide (0.75 mol%) as radical initiating agent and NBS (0.016 mol) in 100
mL of CCl4 under nitrogen atmosphere. The mixture was heated and a solution
of the respective bis(p-methylphenylen)(R)phenylsilane (8x10-2 mol) in CCl4
was slowly added. The system was refluxed for 6 h and then stirred at room
temperature during 24 h. After cooling, the remainder NBS was removed by
filtration and the solution was washed with water. The organic portion was
treated with anh. CaCl2, filtered and the solvent was removed by distillation.
The white solid obtained was used without further purification due to its high
spectroscopic purity.
Bis(p-(carboxymethyl)phenylen)(R)phenylsilanes (4)
The preparation of diphenylacetic acid (4a:R=Me, 4b:R=Ph) derivatives
was realized following techniques already reported by Rotman et al. for
dimethylsilane compounds3. Thus, 3x10-3 mol of the dibenzyl nitrile derivative
was dissolved in 15 mL of DEG and the solution was heated at 40 ºC during 30
min. Then 7 mL of aq. NaOH 50% solution was added and then refluxed at 90
ºC for 48 h. After this, the system was cooled and aq. HCl (5%) solution was
added until pH 1 was obtained. The organic portion was separated and washed
with water and then treated with aq. NaOH 4% solution. The alkaline portion
was acidified with aq. HCl and the crude product obtained was re-dissolved
employing NaOH solution. A semi-solid of adequate spectroscopic purity was
obtained after extracting with Et2O, wash with water, dry with anh. MgSO4 and
distil the solvent.
Bis(p-(carboxymethyl)phenylen)methylphenylsilane (4a): Yield 37%. IR
(KBr) (n) (cm-1): 3396 (COO-H), 3069, 3045 (C-H arom.), 2958, 2922 (C-H
aliph.), 1708 (C=O), 1599, 1427 (C=C arom.), 1397, 1109, 736 (silyl-Ph),
1402, 1251 (silyl-CH3), 785, 700 (arom. p-subst.), 723 (arom. mono-subst.).
1H NMR (CDCl3) (d) (ppm): 0.82 (s,3H,Si-CH3), 3.66 (s,4H,CH2), 7.27-7.79
(m,13H,Ph-H), 10.0 (s,2H,COOH). 13C NMR (CDCl ) (d) (ppm): -3.37 (Si-
CH3), 41.1 (CH2), 127.9 (C7), 128.8 (C3), 128.9 (C8),3134.5 (C1), 134.9 (C5),
135.8 (C4), 136.4 (C2), 136.7 (C6), 177.5 (COOH). 29Si NMR (CDCl3) (d)
(ppm): -10.8.
Bis(p-(bromomethyl)phenyenl)methylphenylsilane (2a): Yield 32%, mp
120-122 ºC. IR (KBr) (n) (cm-1): 3067 (C-H arom.), 2957, 2928 (C-H aliph.),
1598, 1503 (C=C arom.), 1426, 1109, 726 (silyl-Ph), 1228, 787 (silyl-CH3), 832,
700 (arom. p-subst.), 745 (arom. mono-subst.), 605 (C-Br). 1H NMR (CDCl3)
(d) (ppm): 0,86 (s,3H,Si-CH3), 4,52 (s,4H,CH2), 7,24-7,68 (m,13H,Ph-H). 13
C
NMR (CDCl3) (d) (ppm): -3.39 (Si-CH3), 33.3 (CH2), 120.0 (C7), 129.7 (C3),
129.7 (C8), 134.3 (C6), 135.6 (C2), 136.4 (C5), 137.0 (C1), 139.1 (C4). 29Si
NMR (CDCl3) (d) (ppm): -10.8.
Bis(p-(bromomethyl)phenylen)diphenylsilane (2b): Yield 38%, mp 211-
214 ºC. IR (KBr) (n) (cm-1): 3066 (C-H arom.), 2957, 2916 (C-H aliph.), 1484,
1427 (C=C arom.), 1395, 1108, 726 (silyl-Ph), 785, 700 (arom. p-subst.), 737
1
(arom. mono-subst.), 606 (C-Br). H NMR (CDCl3) (d) (ppm): 4.52 (s,4H,CH2),
7.21-7.72 (m,18H,Ph-H). 13C NMR (CDCl ) (d) (ppm): 33.3 (CH ), 125.9 (C7),
128.0 (C3), 125.8 (C8), 129.9 (C6), 130.23(C2), 134.5 (C5), 1362.3 (C1), 139.2
(C4). 29Si NMR (CDCl3) (d) (ppm): -14.3.
Bis(p-(cianomethyl)phenylen)(R)phenylsilanes (3)
Bis(p-(carboxymethyl)phenylen)diphenylsilane (4b): Yield 41%. IR (KBr)
(n) (cm-1): 3404 (COO-H), 2995, 2980 (C-H arom.), 2941, 2875 (C-H aliph.),
1757 (C=O), 1523, 1400 (C=C arom.), 1377, 1158, 726 (silyl-Ph), 869, 717
(arom. p-subst.), 745 (arom. mono-subst.). 1H NMR (CDCl3) (d) (ppm): 3.55
(s,4H,CH ), 7.18-7.61 (m,18H,Ph-H), 8.78 (s,2H,COOH). 13C NMR (CDCl3)
(d) (ppm)2: 41.3 (CH2), 128.0 (C7), 128.1 (C1), 129.1 (C3), 129.8 (C8), 134.1
(C5), 135.3 (C4), 136.5 (C6), 136.8 (C2), 177.0 (COOH). 29Si NMR (CDCl3)
(d) (ppm): -14.5.
These syntheses were developed following classic references for phase-
transfer reactions31. Sodium cyanide (0.10 mol) and TBAB (1x10-2 mol)
were dissolved in 40 mL of water. The solution was stirred for 15 min. at a
temperature close to 50 ºC. Later, the mixture was cooled at room temperature
and 5x10-2 mol of the respective dibenzyl bromide derivative dissolved in 20
mL of CHCl3 was added. The systems was refluxed for 2 h and then cooled.
Three portions of water were used for removing salts and the organic portion
was treated with anh. CaCl2. After filtration the solvent was removed and the
crude product was dried at 50 ºC during 12 h.
Bis(p-(aminomethyl)phenylen)(R)phenylsilanes (5)
3b (R = Ph) was successively recrystallized from ethanol in order to obtain
a white solid, while 3a (R= Me) was dissolved in n-hexane and purified by
chromatographic techniques using silica gel (Merck, 70-230 mesh) and a
mixture of n-hexane/ethyl acetate (90/10 vol/vol) as eluent.
The phenethylamine (5a:R=Me, 5b:R=Ph) derivatives were synthesized
by reduction of the dibenzyl nitrile compounds according to described
procedures1,3. Thus, 5x10-2 mol of the respective bis(p-(cianomethyl)phenylen)
(R) phenylsilane was dissolved in 70 mL of THF and placed in a water-ice
bath. Then a solution of 3x10-2 mol of LiAlH4 in 100 mL of THF was slowly
added. The system was refluxed for 4 h and then stirred at room temperature
during 12 h. After this, the system was cooled at 0 ºC and 5 mL of water were
added with stirring for 1 h. After filtration, the solution was treated with anh.
CaCl2 and the solvent removed by distillation.
Bis(p-(aminomethyl)phenylen)methylphenylsilane (5a): Yield 58%. IR
(KBr) (n) (cm-1): 3373 (N-H), 3066, 3011 (C-H arom.), 2954, 2851 (C-H
aliph.), 1599, 1427 (C=C arom.), 1394, 1109, 726 (silyl-Ph), 1394, 1252
(silyl-CH3), 784, 699 (arom. p-subst.), 723 (arom. mono-subst.). 1H NMR
(CDCl3) (d) (ppm): 0.93 (s,3H,Si-CH3), 1.97 (s,4H,NH2), 2.68-2.80 (t,4H,Ph-
CH2), 2.82-3.00 (t,4H,CH2-N), 7.14-7.78 (m,13H,Ph-H). 13C NMR (CDCl3) (d)
(ppm): -3.00 (Si-CH3), 40.1 (Ph-CH ), 43.4 (CH -N), 127.6 (C3), 128.6 (C7),
129.5 (C8), 132.8 (C1), 135.4 (C2),2136.2 (C6),2 139.7 (C5), 141.2 (C4). 29Si
NMR (CDCl3) (d) (ppm): -10.6.
Bis(p-(cianomethyl)phenylen)methylphenylsilane (3a): Yield 38%, mp 35-
38 ºC. IR (KBr) (n) (cm-1): 3068 (C-H arom.), 2959 (C-H aliph.), 2250 (CN),
1599, 1427 (C=C arom.), 1395, 725 (silyl-Ph), 1257, 784 (silyl-CH3), 806, 699
(arom. p-subst.), 725 (arom. mono-subst.). 1H NMR (CDCl3) (d) (ppm): 0.83
(s,3H,Si-CH3), 3.69 (s,4H,CH ), 7.28-7.58 (m,13H,Ph-H). 13C NMR (CDCl )
(d) (ppm): -3.38 (Si-CH3), 232.6 (CH2), 117.8 (CN), 127.6 (C7), 128.2 (C83),
128.8 (C4), 129.9 (C3), 131.5 (C1), 135.2 (C2), 135.9 (C5), 136.1 (C6). 29Si
NMR (CDCl ) (d) (ppm): -10.6.
Bis(p-(ci3anomethyl)phenylen)diphenylsilane (3b): Yield 47%, mp 137-
139 ºC. IR (KBr) (n) (cm-1): 3067 (C-H arom.), 3025, 2915 (C-H aliph.),
2250 (CN), 1598, 1427 (C=C arom.), 1415, 1109, 726 (silyl-Ph), 799, 702
(arom. p-subst.), 737 (arom. mono-subst.). 1H NMR (CDCl3) (d) (ppm):
3.76 (s,4H,CH2), 7.24-7.57 (m,18H,Ph-H). 13C NMR (CDCl ) (d) (ppm): 23.6
(CH2), 117.6 CN), 127.5 (C7), 128.1 (C3), 129.9 (C8), 131.53(C4), 133.2 (C5),
134.1 (C1), 136.5 (C6), 137.1 (C2). 29Si NMR (CDCl3) (d) (ppm): -14.4.
Bis(p-(aminomethyl)phenylen)diphenylsilane (5b): Yield 55%. IR (KBr)
(n) (cm-1): 3359 (N-H), 3067, 3011 (C-H arom.), 2919, 2851 (C-H aliph.), 1599,
1428 (C=C arom.), 1393, 1108, 726 (silyl-Ph), 803, 701 (arom. p-subst.), 745
(arom. mono-subst.). 1H NMR (CDCl3) (d) (ppm): 2.12 (s,4H,NH ), 2.72-2.79
(t,4H,Ph-CH ), 2.80-3.01 (t,4H,CH -N), 7.12-7.76 (m,18H,Ph-H)2. 13C NMR
(CDCl3) (d) 2(ppm): 39.9 (Ph-CH2)2, 43.2 (CH2-N), 127.8 (C3), 128.5 (C7),
138