Synthesis of t-Boc-protected 4,40-diaminodeoxybenzoin (3)
solvent under reduced pressure, the side product triethylamine
hydrochloride was removed by washing with anhydrous
dichloromethane under nitrogen atmosphere. Further drying
under vacuum afforded the product as a pale brown solid (3.9 g,
To a two-neck round bottom flask were added t-Boc-protected
4,40-diaminobenzil 2 (17.5 g, 40 mmol) and 200 mL of pyridine.
Hydrogen sulfide gas was bubbled into the solution through
a septum in a sidearm of the flask (the outlet of the reaction vessel
was connected to a trap containing aqueous sodium hydroxide
solution (10%) to quench the unreacted H2S gas). As the reaction
progressed, the solution changed from pale yellow to deep red,
and a separation of yellow solid (sulfur) was observed. As the Rf
values of both starting material and product were very similar, it
was difficult to follow the reaction progress by TLC. Monitoring
the reaction by 1H NMR indicated that the reaction was
complete after 8 h of H2S bubbling. Excess pyridine was removed
under reduced pressure. The residue was poured into dilute
hydrochloric acid (5%), and the resulting off-white solid was
isolated by filtration. Further washing with water, drying under
vacuum, and purification by column chromatography (1 : 5
mixtures of ethyl acetate and hexane) afforded the desired
1
79% yield). H NMR (acetone-d6, 400 MHz): 3.99 (s, 2H), 6.60
(m, 2H), 6.67 (m, 2H), 6.99 (m, 2H), 7.83 (m, 2H). 13C NMR
(DMSO-d6, 100 MHz): 196.0, 145.7, 139.0, 138.8, 131.5, 130.5,
124.7, 124.2, 118.01, 116.3, 112.5, 43.7. FT-IR (cmꢁ1): n 3312,
2978, 2603, 2497, 2267, 1747, 1664, 1599, 1523, 1475, 1409, 1308,
1220, 1180, 1157, 1036, 993, 830, 761. HRMS-FAB: m/z M+ calcd
278.0691; found 278.0684.
Synthesis of 4,40-[bis-(2-hydroxyethoxy)]deoxybenzoin (6)
To a round bottom flask was added 4,40-bishydroxydeoxy-
benzoin (3 g, 13.15 mmol), ethylene carbonate (2.43 g,
27.6 mmol) and sodium carbonate (0.1 g, 0.9 mmol), and the
mixture was heated with stirring at 180 ꢂC for 4 h. The melt was
then cooled to room temperature and the solidified product was
washed with water to retrieve the product as a pale yellow solid
(3.9 g, 94%); mp 130 ꢂC. 1H NMR (400 MHz, DMSO-d6, ppm):
3.72 (m, 4H), 3.94 (t, 2H), 4.07 (t, 2H), 4.21 (s, 2H), 4.84 (t, 1H),
4.91 (t, 1H), 6.86 (m, 2H), 7.03 (m, 2H), 7.16 (m, 2H), 8.0
(m, 2H). 13C NMR (DMSO-d6, 100 MHz): 196.4, 162.7, 157.4,
130.8, 130.6, 129.2, 127.3, 114.4, 114.2, 70.0, 69.5, 59.7, 59.5,
43.6. FT-IR (cmꢁ1): n 3347, 2953, 1682, 1599, 1512, 1454, 1417,
1334, 1302, 1220, 1172, 1043, 995, 912, 828, 772, 674. HRMS-
FAB: m/z [M + 1]+ calcd 317.1311; found 317.1391.
1
product as white fluffy solid (16 g, 94% yield); mp 203 ꢂC. H
NMR (acetone-d6, 400 MHz): 1.49 (s, 9H), 1.46 (s, 9H), 4.23
(s, 2H), 7.21 (m, 2H), 7.48 (m, 2H), 7.66 (m, 2H), 8.02 (m, 2H),
8.34 (bs, 1H), 8.79 (bs, 1H). 13C NMR (acetone-d6, 100 MHz):
196.6, 153.7, 153.4, 145.1, 139.1, 131.7, 130.7, 130.6, 130.2, 119.1,
118.1, 80.7, 79.8, 44.9, 28.5, 28.4. FT-IR (cmꢁ1): n 3371, 2977,
1705, 1682, 1605, 1525, 1502, 1409, 1392, 1368, 1319, 1235, 1121,
1155, 1057, 996, 904, 826, 772. HRMS-FAB: m/z M+ calcd
426.2155; found 426.2136.
Synthesis of 4,40-diaminodeoxybenzoin (4)
General procedure for the synthesis of polyurethanes
To an ice-cooled solution of t-Boc-protected 4,40-diaminodeoxy-
benzoin 3 (16 g, 37 mmol) in 200 mL of anhydrous dichloro-
methane was added trifluoroacetic acid (38.9 g, 336 mmol) in
a dropwise manner. During the addition, the solution became
homogeneous and red. The mixture was stirred at room
temperature for 24 h. A brown solid (ammonium salt) separated
during the course of the reaction. The mixture was filtered and
washed with dichloromethane to remove organic soluble impu-
rities. The solid so obtained was then dissolved in water,
neutralized by addition of sodium carbonate, and the precipi-
tated product was extracted with ethyl acetate. The organic
layers were combined, washed with water, dried over anhydrous
magnesium sulfate and concentrated to give a brown solid (5.9 g,
To a flame-dried round bottom flask was added diisocyanate
(1 equiv), diol (1 equiv) and dibutyltin dilaurate (0.1 equiv) in
anhydrous N-methyl pyrrolidone (10 mL per 2 g of diisocyanate
batch). The mixture was heated at 120 ꢂC for 24 h. After cooling
to room temperature, the reaction mixture was added dropwise
to an excess of methanol (ꢀ1 L). The precipitate obtained was
washed with methanol, then with water and again with methanol
to obtain off-white or pale yellow solid as the product.
Data for polyurethanes
Polyurethane 9 (DBDI + deoxybenzoin diol, 6). Yield: 70%. 1H
NMR (DMSO-d6, 400 MHz): 3.69 (t, 2H), 3.73 (t, 2H), 3.93
(t, 2H), 4.06 (t, 2H), 4.0 (s, 2H), 4.21 (s, 2H), 6.88 (m, 2H), 7.05
(m, 2H), 7.16 (m, 4H), 7.37 (m, 2H), 7.60 (m, 2H), 7.99 (m, 4H),
8.58 (bs, 1H), 9.75 (bs, 1H). FT-IR (cmꢁ1): n 3322, 2930, 1714,
1672, 1597, 1512, 1414, 1314, 1216, 1172, 1061, 993, 922, 833.
ꢂ
1
70% yield); mp 137 C. H NMR (acetone-d6, 400 MHz): 3.99
(s, 2H), 4.46 (bs, 2H), 5.44 (bs, 2H), 6.60 (m, 2H), 6.67 (m, 2H),
6.99 (m, 2H), 7.83 (m, 2H). 13C NMR (acetone-d6, 100 MHz):
196.2, 154.2, 147.6, 131.8, 130.7, 126.5, 120.2, 115.2, 113.7, 44.5.
FT-IR (cmꢁ1): n 3329, 3228, 1682, 1659, 1627, 1589, 1565, 1514,
1437, 1329, 1302, 1229, 1171, 991, 807, 772. HRMS-FAB:
m/z [M + 1]+ calcd 227.1106; found 227.1176.
Polyurethane 10 (MDI + deoxybenzoin diol, 6). Yield: 64%. 1H
NMR (DMSO-d6, 400 MHz): 3.79 (m, 4H), 3.92 (t, 2H), 4.05
(t, 2H), 4.22 (s, 2H), 6.6 (m, 2H), 6.8 (m, 2H), 7.05 (m, 4H), 7.35
(m, 4H), 7.16 (m, 2H), 8.00 (m, 2H), 8.53 (bs, 1H), 9.71 (bs, 1H).
FT-IR (cmꢁ1): n 3312, 2927, 1704, 1678, 1597, 1537, 1510, 1413,
1305, 1220, 1173, 1110, 1059, 995, 916, 818, 771.
Synthesis of 4,40-deoxybenzoin diisocyanate (5)
To a flame-dried round bottom flask was added 4,40-dia-
minodeoxybenzoin, 4 (4.0 g, 17 mmol). This was dried under
vacuum for 3–4 h, then purged with nitrogen. To this was added
triphosgene (3.7 g, 12 mmol), anhydrous triethylamine (1.26 g,
12.5 mmol) and anhydrous THF (60 mL). The mixture was
stirred at room temperature for 4 h. After removing excess
Polyurethane 11 (TDI + deoxybenzoin diol, 6). Yield: 70%. 1H
NMR (DMSO-d6, 400 MHz): 2.12 (s, 3H), 3.93 (t, 2H), 4.07
(t, 2H), 4.18 (t, 2H), 4.23 (s, 2H), 4.32 (t, 2H), 6.70 (m, 2H), 7.02
(m, 3H), 7.17 (m, 3H), 7.52 (m, 1H), 8.01 (m, 2H), 8.98 (bs, 1H),
3686 | J. Mater. Chem., 2010, 20, 3681–3687
This journal is ª The Royal Society of Chemistry 2010