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M. Danko et al. / Dyes and Pigments 90 (2011) 129e138
the filtration of the inorganics, the solvents were evaporated and the
product was separated on a silica column using i-hexane/ethyl-
acetate (5/1, v/v) as the eluent, yielding 1.56 g (75%) of white powder.
BOC-NOR (1.55 g) was treated with CF3COOH (8 ml, 26 molar
excess) in dichloromethane at r.t. for the deprotection of amine.
Product 6 was formed as a white precipitate after the addition of
a water solution of NaHCO3 to the reaction mixture and was
separated by filtration (yield 1.01 g, 89%). FTIR analysis (KBr pellet)
of the washed and dried white powder did not show carboxyamide
absorption. For further reactions, 6 was used as the crude product.
All protection, N-oxyl formation and deprotection products
were analyzed by FTIR analysis in chloroform solution.
a hydrochloride salt. Another portion of the product was formed
during the evaporation of the THF solvent from the reaction mixture.
The pure parent amine was separated by extraction of a CHCl3
solution of hydrochloride with a water solution of NaHCO3, followed
by extraction with NaCl and water. The total yield of the parent
amine of 2a was 27% of white crystals, with a m.p. of 228e230 ꢀC.
1H NMR (CDCl3)
d(ppm): 1.07e1.11 (2H, eCHeCH2 equat.); 1.17
(s, 6H, eCH3 equat.); 1.24 (t, 6H, 2 ꢁ CH3eCH2eNe, J ¼ 7.14 Hz);
1.31 (s, 6H, eCH3 axial); 2.0 (dd, 2H, eCHeCH2 axial); 3.45 (q, 4H,
2 ꢁ CH3eCH2eNe, J ¼ 7.12 Hz); 4.36e4.52 (tm, 1H, eCHe); 6.50 (d,
1H, coumarin H-8); 6.65 (dd, 1H, coumarin H-6, J ¼ 8.95 Hz); 7.43
(d, 1H, coumarin H-5, J ¼ 8.96 Hz); 8.64 (d, 1H, eNHe); 8.68 (s, 1H,
>C]CHemethylene).
2.1.4. Coumarin-3-carboxy-(1-(10-phenylethyl)oxy-2,2,6,6-
tetramethylpiperidine-4-yl)amide (1c)
13C NMR (CDCl3)
d(ppm): 12.4 (CH3eCH2e); 28.5 (CH3 axial);
34.9 (CH3 equat.); 42.7 (CHeN); 45.1 (CH2eCHeN); 45.2
(CH3eCH2e); 51.1 (CeN); 96.5 (CH-8 coumarin); 108.4 (C-10
coumarin); 109.9 (C-5 naphthalene); 110.4 (C-3 lactone); 131.1
(eCH]methylene); 147.9 (CH-6 coumarin); 152.4 (C-9 coumarin);
157.6 (C-7 coumarin); 162.2 (C]O lactone); 162.7 (C]O amide).
The synthesis of 1c was carried out using mediator 7, similar to
that of 1b. 1 (0.63 g, 3.3 mmol), reacted with 6 (1.01 g, 10% molar
excess) and 7 (1.01 g,10% molar excess) inTHF solution. Because only
small changes were observed using TLC analysis SiO2 plate, elution
ethylacetate/i-hexane (1/5, v/v) of the reaction mixture stirred at r.t.,
the reaction was continued at 55 ꢀC for 8 h. The formed precipitate
was separated by filtration and thoroughly washed on the funnel
with THF (6 ꢁ 10 ml). The solvent was evaporated on a rotary
evaporator, and the solid residue was separated (chromatographed)
on the silica column using gradient elution of ethylacetate/i-hexane
mixtures, starting with a 1/5 mixture and finishing with pure eth-
ylacetate. Only the last fraction was identified by NMR analysis as
a product; preceding fractions did not contain NMR signals related
to the coumarin fluorophore. The yield of coumarin e N-alkoxy-
amine was 28% of theoretical amount of small white crystals with
a m.p. of <120 ꢀC (carbonization).
FTIR (KBr)
n
(cmꢂ1): 3434, 3315, 2974, 1692, 1648, 1618, 1585,
1537, 1513, 1413, 1355, 1244, 1191, 1136, 798.
Anal. Calcd. for C23H33N3O3: C69.14, H8.33, N10.52. Found:
C68.55, H8.25, N10.25.
2.1.7. 7-(N,N-diethylamino)coumarin-3-carboxy-(1-oxo-2,2,6,6-
tetramethylpiperidine-4-yl)amide (2b)
The synthesis of 2b was carried out using a DMT-MM mediator,
similar to that of 1b, using compounds 2 (1.92 mmol), 5 (2.11 mmol)
and 7 (2.11 mmol) in THF solution over 18 h. The FTIR analysis of the
reaction mixture showed formation of eC]O vibration related to
the amide. After the THF evaporation, the residue was dissolved in
chloroform, extracted with brine solution and water and dried over
anhydrous Na2SO4. The product was obtained by chromatographic
separation on a SiO2 column using a CHCl3/MeOH mixture (15/1, v/v)
as the first fraction. Yellow-orange crystals of 2b, with a m.p. of
263e267 ꢀC, were obtained by crystallization from the elution
solution during evaporation in 50% yield. The purity of product (98%)
was confirmed by ESR analysis comparing with 4-hydroxy-1-oxy-
2,2,6,6-tetramethylpiperidine in toluene solution (1 ꢁ10ꢂ3 mol Lꢂ1).
1H NMR (CDCl3)
d(ppm): 0.68 (s, 3H, 1 ꢁ CH3 equatorial); 1.17 (s,
6H, 1 ꢁ CH3 equatorial); 1.32e1.35 (2 ꢁ s, 6H, 2 ꢁ eCH3 axial); 1.5
(d, 3H, eCHeCH3, J ¼ 6.68 Hz); 1.57 (t, 2H, eCHeCH2 equatorial);
1.80 (td,1H, eCHeCH2 axial); 1.93 (td,1H, eCHeCH2 axial); 4.31 (m,
1H, eCHeNHe); 4.79 (q, 1H, eCHeCH3, J ¼ 6.68 Hz) 7.20e7.32 (m,
5H, 1-Phenyl); 7.34e7.43 (m, 2H, coumarin); 7.62e7.72 (m, 2H,
coumarin); 8.59 (d, 1H, eNHeCHe); 8.87 (s, 1H, >C]
CHemethylene).
13C NMR (CDCl3)
d(ppm): 20.9 (CH3eCHePh); 23.3 (CH3 axial);
1H NMR (CDCl3, reduced by pentafluorophenyl hydrazine)
d
30.9 (>CHeCH3); 34.0 and 34.3 (CH3 equat.); 41.7 (CHeNH); 45.9
(CH2eCHeN); 59.8 and 60.1 (2 ꢁ CeN); 83.3 (CH3eCHePh); 116.6
(CH-8 coumarin); 118.6 (C-3 lactone); 118.7 (C-10 coumarin); 125.2
(CH-6 coumarin); 126.7 (CH-2,6 phenyl); 126.9 (CH-4 phenyl);
128.0 (CH-3,5 phenyl); 129.8 (C-5 coumarin); 133.9 (eCH]meth-
ylene); 145.4 (C-1 phenyl); 148.1 (C-7 coumarin); 154.4 (C-9
coumarin); 160.7 (C]O lactone); 161.4 (C]O amide).
(ppm): 1.25 (t, 6H, 2 ꢁ CH3eCH2eNe); 1.44; (s, 6H, eCH3 equat.);
1.49 (s, 6H, eCH3 axial); 2.04 (t, 2H, eCHeCH2 equat.); 2.19 (dd, 2H,
eCHeCH2 axial); 3.46 (q, 4H, 2 ꢁ CH3eCH2eNe); 4.01 (strong
singlet, residual from pentafluorophenyl hydrazine); 4.45e4.62 (m,
1H, eCHe); 5.16 (wide, 1H, >NeOH); 6.50 (d, 1H, coumarin); 6.67
(dd, 1H, coumarin); 7.44 (d, 1H, coumarin); 8.65 (s, 1H, >C]
CHemethylene); 8.82 (d, 1H, eNHe).
FTIR (KBr)
n
(cmꢂ1): 3451, 3328, 2974, 2934, 1714, 1655, 1613,
FTIR (KBr) n
(cmꢂ1): 3439, 3301, 3040, 2975, 2935, 1706, 1659,
1570, 1539, 1457, 1365, 1241, 1078, 948, 799, 759, 699, 633.
Anal. Calcd. for C27H32N2O4: 72.30, H7.19, N6.25. Found: C72.18,
H7.22, N5.44.
1609, 1565, 1543, 1452, 1362, 1238, 1145, 798, 768, 642.
2.1.8. 7-(N,N-diethylamino)coumarin-3-carboxy-(1-(10-
phenylethyl)oxy-2,2,6,6-tetramethylpiperidine-4-yl)amide (2c)
The synthesis of 2c was carried out using DMT-MM mediator,
similar to that of 1c, using compounds 2 (1.16 mmol), 6 (1.27 mmol)
and 7 (1.27 mmol) in THF solution over 48 h. The formed precipitate
was separated by filtration and thoroughly washed on the funnel
with THF (6 ꢁ 10 ml). The solvent was evaporated on a rotary
evaporator, and the solid residue was chromatographed on a silica
column using gradient elution of i-hexane/ethylacetate mixtures,
beginning with a 1/1 mixture (v/v) and finishing with a 1/2 mixture
(v/v). Orange crystals of 2c with a m.p. of 230e232 ꢀC were
obtained by crystallization from the elution solution during evap-
oration in 27% yield.
2.1.5. 7-N,N-diethylaminocoumarin-3-carboxylic acid (2)
Product 2 was prepared according to the procedure of Song et al.
[37] in 63% yield. The product was crystallized from the reaction
mixture after cooling to ꢂ25 ꢀC as orange crystals with a m.p. of
230e232 ꢀC (ref. [37] m.p. 222e224 ꢀC) and was used for next step
without further purification. The chemical structure and purity of
this compound were proven by 1H NMR.
2.1.6. 7-(N,N-diethylamino)coumarin-3-carboxy-(2,2,6,6-
tetramethylpiperidine-4-yl)amide (2a)
The synthesis of 2a was performed as for 1a, using compounds 2
(1.16 mmol), 4 (1.27 mmol) and 7 (1.27 mmol) in THF solution for
18 h. The product was crystallized from the reaction mixture as
1H NMR (CDCl3)
3H, 1 ꢁ CH3 equat.); 1.26 (t, 6H, 2 ꢁ CH3eCH2eNe); 1.31e1.34
d(ppm): 0.67 (s, 3H, 1 ꢁ CH3 equat.); 1.17 (s,