Green protocol for conjugate addition of amines
1319
2-(Propylamino)cyclohexa-2,5-diene-1,4-dione
and secondary amines underwent smooth additions
with p-quinones in H2O in absence of a catalyst. The
scope and generality of this process is illustrated
in Table 1. In conclusion, we have developed an
efficient and greener protocol for the synthesis of
2-amino-p-quinones in H2O. This method offers sev-
eral advantages including mild reaction conditions,
enhanced rates, cleaner reactions with improved
yields, no production of by-products, and ready
availability of starting materials, high regioselectiv-
ity, operational and experimental simplicity which
makes this method a useful and attractive strategy
for the synthesis of 2-amino-p-quinones.
(3h, C9H11NO2)
Solid, mp 110–112ꢀC; 1H NMR (200MHz, CDCl3): ꢀ ¼
0.992–1.03 (m, 3H), 1.62–1.69 (m, 2H), 3.10–3.15 (m, 2H),
5.19 (s, 1H), 6.51–6.61 (s, 2H) ppm; IR (KBr): ꢁꢀmax ¼ 3454,
3314, 2932, 2852, 1609, 1573, 1482, 1213, 1201, 1149,
753 cmꢁ1; HRMS (ESI): m=z calcd for C9H12NO2 166.0868,
found 166.0860.
2-(Phenlamino)cyclohexa-2,5-diene-1,4-dione (3j, C12H9NO2)
Solid, mp 131–133ꢀC; 1H NMR (200MHz, CDCl3): ꢀ ¼
6.55–6.61 (m, 4H), 6.91–7.05 (m, 3H), 8.1 (s, 1H) ppm; IR
(KBr): ꢁꢀmax ¼ 3465, 3312, 2932, 2855, 1609, 1571, 1471,
1222 1201, 1152, 755 cmꢁ1; HRMS (ESI): m=z calcd for
C12H10NO2 200.0711, found 200.0702.
2-(p-Tolylamino)cyclohexa-2,5-diene-1,4-dione
(3k, C13H11NO2)
Experimental
Solid, mp 137–139ꢀC; 1H NMR (200 MHz, CDCl3): ꢀ ¼ 2.35
(s, 3H), 6.53 (s, 1H), 6.83 (d, J ¼ 8.7 Hz, 1H), 7.08–7.22 (m,
4H), 7.26 (d, J ¼ 8.7 Hz, 1H) ppm; IR (KBr): ꢁꢀmax ¼ 3445,
3310, 2932, 2886, 1662, 1642, 1553, 1297, 1108, 968, 866,
774 cmꢁ1; HRMS (ESI): m=z calcd for C13H11NO2Na
236.0653, found 236.0647.
Melting points were recorded on a Bu¨chi R-535 apparatus. IR
spectra were recorded on a Perkin-Elmer FT-IR 240-c spectro-
photometer using KBr optics. 1H NMR spectra were recorded
on Gemini-200 and Varian Bruker-300 spectrometers in CDCl3
using TMS as internal standard. Mass spectra were recorded on
a Finnigan MAT 1020 mass spectrometer operating at 70 eV.
2-(4-Methoxyphenylamino)cyclohexa-2,5-diene-1,4-dione
(3l, C13H11NO3)
Typical procedure
A mixture containing 1 mmol p-quinone 1, 1 mmol amine 2 in
1 cm3 water was stirred at 50–70ꢀC for the specified time (see
Table 1). After completion of the reaction, the crude product
was filtered off, washed with water, and dried under reduced
pressure to afford pure 2-aminoquinone which was purified by
chromatography.
Solid, mp 132–134ꢀC; 1H NMR (200MHz, CDCl3): ꢀ ¼ 3.50
(s,3H),6.75(s,1H),6.81(d,J ¼ 8.7Hz,1H),6.92–7.02(m,4H),
7.23 (d, J ¼ 8.7 Hz, 1H) ppm; IR (KBr): ꢁꢀmax ¼ 3454, 3324,
2931, 2872, 1609, 1571, 1481, 1223, 1154, 753 cmꢁ1; HRMS
(ESI): m=z calcd for C13H12NO3 230.0817, found 230.0810.
3,5-Dimethyl-2-(Propylamino)cyclohexa-2,5-diene-1,4-dione
2-(Diethylamino)naphthalene-1,4-dione (3b, C14H15NO2)
Solid, mp 125–127ꢀC; 1H NMR (200MHz, CDCl3): ꢀ ¼
1.29–1.32 (m, 6H), 3.51–3.60 (m, 4H), 5.85 (s, 1H), 7.56–
(3n, C11H15NO2)
1
Solid, mp 80–82ꢀC; H NMR (200 MHz, CDCl3): ꢀ ¼ 0.99–
1.02 (m, 3H), 1.65–1.73 (m, 2H), 2.14 (s, 3H), 2.35 (s, 3H),
3.02–3.15 (m, 2H), 6.02 (s, 1H) ppm; IR (KBr): ꢁꢀmax ¼ 3451,
3312, 2923, 2853, 1662, 1642, 1521, 1282, 1232, 1172, 1034,
956 cmꢁ1; HRMS (ESI): m=z calcd for C11H16NO2 194.1181,
found 200.0702.
7.74 (m, 2H), 7.95–8.06 (m, 2H) ppm; IR (KBr): ꢁꢀmax
3452, 3302, 2933, 2871, 1605, 1591, 1482, 1208, 1123,
765 cmꢁ1
HRMS (ESI): m=z calcd for C14H16NO2
¼
;
230.1181, found 230.1172.
2-(4-Phenylpiperazin-1-yl)naphthalene-1,4-dione
(3d, C20H18N2O2)
3,5-Dimethyl-2-morpholinocyclohexa-2,5-diene-1,4-dione
(3o, C12H15NO3)
Solid, mp 141–143ꢀC;1H NMR (200MHz, CDCl3):ꢀ ¼ 3.38 (t,
J ¼ 10.5Hz, 4H), 3.70 (t, J ¼ 10.5 Hz, 4H), 6.03 (s, 1H), 6.84–
6.91 (m, 2H), 7.21–7.27 (m, 3H), 7.61–7.72 (m, 2H), 7.99–
8.05 (m, 2H) ppm; IR (KBr): ꢁꢀmax ¼ 3452, 3312, 2945, 2864,
1613, 1583, 1482, 1221, 1218, 1123, 773 cmꢁ1; HRMS (ESI):
m=z calcd for C20H18N2O2Na 341.1265, found 341.1255.
Solid, mp 91–93ꢀC, 1H NMR (200MHz, CDCl3): ꢀ ¼ 2.21 (s,
3H), 2.30 (s, 3H), 3.52 (t, J ¼ 8.5 Hz, 4H), 3.82 (t, J ¼ 8.5 Hz,
4H), 6.23 (s, 1H) ppm; IR (KBr): ꢁꢀmax ¼ 3435, 3312, 2985,
1614, 1583, 1456, 1435, 1208, 1155cmꢁ1; HRMS (ESI): m=z
calcd for C12H16NO3 222.1130, found 222.1120.
3,5-Dimethyl-2-(phenylamino)cyclohexa-2,5-diene-1,4-dione
2-(p-Tolylamino)naphthalene-1,4-dione (3f, C17H13N2O2)
Solid, mp 135–138ꢀC; 1H NMR (200 MHz, CDCl3): ꢀ ¼ 2.02
(s, 3H), 6.35 (s, 1H), 7.15–7.25 (m, 2H), 7.32–7.41 (m, 2H),
7.60–7.72 (m, 2H), 8.12 (d, J ¼ 8.0 Hz, 2H) ppm; IR
(KBr): ꢁꢀmax ¼ 3445, 3323, 2924, 2832, 1651, 1612, 1518,
1462, 1236, 1164, 1023, 825, 732 cmꢁ1; HRMS (ESI): m=z
calcd for C17H14N2O2 264.1024, found 264.1015.
(3p, C14H13NO2)
1
Solid, mp 75–77ꢀC; H NMR (200MHz, CDCl3): ꢀ ¼ 1.45
(s, 3H), 2.15 (s, 3H), 6.59–6.62 (m, 2H), 6.83 (d, J ¼ 8.0 Hz,
2H), 6.94 (d, J ¼ 8.0 Hz, 2H) ppm; IR (KBr): ꢁꢀmax ¼ 3452,
3315, 2927, 2855, 1660, 1632, 1521, 1262, 1170, 1033, 962,
764 cmꢁ1; HRMS (ESI): m=z calcd for C14H14NO2 228.1024,
found 228.1014.