Acylation of o-imidoylphenol lithium dianions: Synthesis of 4H-chromen- 4-ylidenamines

Article abstract of DOI:10.1016/S0040-4020(99)01029-7

A method is described to obtain 4H-chromen-4-ylidenamines 4, through the reaction of o-imidoyl phenol dianions 2' with aromatic esters and subsequent acid cyclisation of the 3-(2-hydroxyphenyl)-3-(amino)-1-phenylprop-2-en-1- ones 3 obtained. (C) 2000 Else

Full text of DOI:10.1016/S0040-4020(99)01029-7

TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 475–478
Acylation of o-Imidoylphenol Lithium Dianions: Synthesis of
4H-Chromen-4-ylidenamines
*
Cristina Cimarelli and Gianni Palmieri
`
Dipartimento di Scienze Chimiche, Universita di Camerino, Via S. Agostino 1, I-62032 Camerino, Italy
Received 4 October 1999; revised 8 November 1999; accepted 18 November 1999
Abstract—A method is described to obtain 4H-chromen-4-ylidenamines 4, through the reaction of o-imidoyl phenol dianions 20 with
aromatic esters and subsequent acid cyclisation of the 3-(2-hydroxyphenyl)-3-(amino)-1-phenylprop-2-en-1-ones 3 obtained. ᭧ 2000
Elsevier Science Ltd. All rights reserved.
Chromones and flavones belong to a widely explored family
of organic compounds largely present in the plant kingdom.
Flavones and flavonoids show a general tendency to have
biological activity and many compounds have found uses in
medicine and industry.1 4H-Chromen-4-ylidenamines 4 are
derivatives of flavones, almost absent from the literature,
that have awakened new interest because the simplest of
them (2-phenyl-4H-chromen-4-imine), has been the object
of patents2 for treatment of cell proliferative diseases and for
its antihypoxic, hypotensive, and antiallergic properties.
secondary amines results in the opening of the pyran ring,
yielding the corresponding enamino ketone 7, which reverts
the starting material in acidic medium as shown in Scheme
2(a). On the other hand Zagorevskii et al. prepared imino-
chromenes 9 in a very low yield by treatment of 4,4-dichloro-
chromene 8 with primary amines as in Scheme 2(b).4
o-Imidoylphenols 2 can be readily prepared by conden-
sation5 of the appropriate o-acyl phenol 1 and the amine
according to a described procedure.6 Upon treatment with
LDA (lithium diisopropylamide) they give O,C-dianions 20
that can react with electrophiles. We have found that
alkylated o-imidoylphenols can be obtained by alkylation
of these dianions with alkyl halides.7 In the present case the
dianion is allowed to react with aromatic esters and in all the
reactions we have isolated the acylation products
3-(2-hydroxyphenyl)-3-(amino)-1-phenylprop-2-en-1-ones
3. We have found the best results in the acylation reaction
with an excess of 3.5 mol of LDA per mole of starting
We now report the use of o-imidoylphenols 2 as precursors
of 4H-chromen-4-ylideneamines 4, through the reaction of
their dianions with esters, as described in Scheme 1.
Several papers show that it is not possible to prepare
4H-chromen-4-ylidenamines 4 by condensation of the
corresponding chromones with the relevant amine.3 The
reaction of chromone 6 with ammonia and primary and
Scheme 1. (i) RNH2, benzene, Hϩ, reflux; (ii) LDA, 0ЊC, 1 h; (iii) ArCOOR0, Ϫ80ЊC, 2 h; (iv) H3Oϩ, CH2Cl2, rt; (v) H2O/THF/AcOHˆ2/2/1, 40ЊC, 0.5 h.
Keywords: imidoylphenol; chromenes; acylation; cyclisation.
* Corresponding author. Tel.: ϩ39-737-402241; fax: ϩ39-737-637345; e-mail: palmieri@camserv.unicam.it
0040–4020/00/$ - see front matter ᭧ 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(99)01029-7

476
C. Cimarelli, G. Palmieri / Tetrahedron 56 (2000) 475–478
Scheme 2.
material: 2 equiv. are necessary for proton abstraction in
forming the dianion 20, while another metallates the product
30 preventing proton abstraction by 20 more basic that 300.
(Table 1) that was shown by spectroscopy to have a
4H-chromen-4-ylidenamine structure 4.
In summary, starting from cheap and commercially
available starting materials, with known easily performed
procedures, we have found a useful strategy for the
preparation of 4H-chromen-4-ylidenamines 4 in satisfactory
yields, a class of compounds of renewed interest.
The yields obtained in the acylation step (Table 1) are not
very high and moreover are not constant for the same reac-
tion in different preparations: this probably happens because
during the chromatographic purification a partial cyclisation
take place, that we have not quantified. However,
cyclisation by aqueous AcOH, before chromatographic
purification of the crude reaction mixture containing the
acylation product 3ca, resulted in a 78% of yield of the
final 4H-chromen-4-ylidene amine 4ca.
Experimental
1H and 13C NMR spectra were recorded with a Varian VXR
300 instrument. Chemical shifts are given in ppm downfield
from Me4Si in CDCl3 solution. Coupling constants are given
in Hertz. IR spectra were recorded with a Perkin–Elmer 257
spectrometer. GC-MS analyses were performed with an HP
59970 workstation formed by an HP-5890 gas chromato-
graph equipped with a methyl silicone capillary column
and by an HP-5970 mass detector. All melting points are
uncorrected. THF was dried by refluxing over sodium wires
until the blue colour of benzophenone ketyl persisted and
then distilled into a dry receiver under nitrogen atmosphere.
All reagents and solvents were distilled prior to use or were
of commercial quality from freshly opened containers.
Commercial butyllithium solutions (Aldrich) were
employed under dry atmosphere.
Cyclisation also takes place on heating the acylated product.
Enaminoketone 3aa in refluxing toluene after 0.5 h
produces the chromenimine 4aa (64% yield) with a partial
decomposition. For this reason we were unable to register
the mass spectra of all acylated products 3 because GC-MS
analysis showed for every product 3 the mass spectrum of
the corresponding chromen imine 4.
Attempts to perform the reaction with aliphatic esters were
unsuccessful. In the reactions with ethyl propionate and
ethyl phenylacetate, although we could observe in the
mass spectra of both crude reaction mixtures the peaks
corresponding to the chromen imines, all attempts to isolate
the products failed, as the mixtures decomposed after a few
minutes to a blue oil not containing any relevant product.
Preparation of starting 2-imidoyl phenols 2a–c
The 2-imidoyl phenols 2a–c were prepared by condensation
of the appropriate o-acylphenol4 and the amine according to
described procedure.5
The purified 3-(2-hydroxyphenyl)-3-(amino)-1-phenylprop-
2-en-1-ones 3 were heated in acid solution and in all cases a
single product was isolated in almost quantitative yield
Table 1. Acylation of o-imidoyl phenol 2 and cyclisation of the intermedi-
ate hydroxyphenyl enaminone 3 to 4H-chromen-4-ylidene amines 4
Acylation of dianions of 2-imidoyl phenols 2a–c
2-Imidoyl phenols 2a–c (3 mmol) were dissolved in
anhydrous THF (5 cm3) under nitrogen atmosphere at 0ЊC
and treated with a solution in THF of LDA, obtained by
mixing butyllithium (10.5 mmol) with an equimolecular
amount of diisopropylamine in THF (3 cm3). The reaction
mixture was allowed to stand for 1 h, then was cooled to
Ϫ80ЊC and treated with a solution of an aromatic ester
(10.5 mmol) in THF (2 cm3). The reaction was monitored
by TLC with n-hexane/ethyl acetateˆ70/30 as eluent and
after a variable time (2–3 h), when the starting material was
consumed, was quenched with NH4Cl saturated solution
(5 cm3) and brine (2 cm3) and extracted with CH2Cl2
2
R
Ar
3
Yielda (%)
4
Yielda (%)
2a
2a
2a
2b
2b
2c
2c
2c
Me
Me
Me
Pri
Ph
3aa
3ab
3ac
3ba
3bb
3ca
3cb
3cc
72
63
67
42
47
64
37
36
4aa
4ab
4ac
4ba
4bb
4ca
4cb
4cc
92
85
66
72
4-MeO-Ph
4-Py
Ph
4-MeO-Ph
Ph
4-MeO-Ph
4-Py
Pri
81
Bn
Bn
Bn
94 (78)b
87
76
a Of the pure isolated product.
b Yield of the one pot preparation starting from the crude reaction
mixture of 3ca.

C. Cimarelli, G. Palmieri / Tetrahedron 56 (2000) 475–478
477
(2×20 cm3). The solution was dried with anhydrous Na2SO4
then filtered and the solvent evaporated under reduced
pressure. Chromatographic separation of the crude oil
obtained, with cyclohexane/ethyl acetateˆ70/30 as eluent
afforded the acylated product 3 in 36–72% yield.
765, 691 cmϪ1. NMR (CDCl3): dH 4.35 (d, 2 H,
Jˆ6.2 Hz), 5.87 (s, 1 H), 6.40 (br s, 1 H), 6.90–7.90 (m,
14 H), 11.55 (br s, 1 H). dC 49.03, 94.45, 117.02, 121.01,
122.16, 125.16, 126.05, 127.68, 128.03, 128.77, 129.24,
129.35, 131.63, 131.78, 136.22, 137.13, 153.35, 163.00.
Anal. Calcd for C22H19NO2, MW 329.392: C, 80.22; H,
5.81; N, 4.25%. Found: C, 79.97; H, 6.03; N, 4.40%.
(Z)-3-(2-Hydroxyphenyl)-3-(methylamino)-1-phenylprop-
2-en-1-one (3aa). Yellow crystals; mp 128–132ЊC (CH2Cl2/
n-hexane); nmax (Nujol) 1608, 1579, 1342, 1259, 769,
686 cmϪ1. NMR (CDCl3): dH 2.85 (d, 3 H, Jˆ5.3 Hz), 5.78
(s, 1 H), 6.50 (br s, 1 H), 6.92–7.86 (m, 9 H), 11.27 (br s, 1 H).
dC 31.27, 93.44, 116.84, 122.28, 126.00, 127.50, 128.00,
129.00, 130.50, 131.29, 140.31, 153.36, 154.17, 188.64.
Anal. Calcd for C16H15NO2, MW 253.296: C, 75.87; H,
5.97; N, 5.53%. Found: C, 75.76; H, 5.80; N, 5.68%.
(Z)-3-(Benzylamino)-3-(2-hydroxyphenyl)-1-(4-methoxy-
phenyl)prop-2-en-1-one (3cb). Yellow crystals, mp 154ЊC
(CH2Cl2/n-hexane); nmax (Nujol) 1733.8, 1611.7, 1565.9,
1247.7, 1168.0, 699.2 cmϪ1. NMR (CDCl3): dH 3.83 (s, 3
H), 4.31 (d, 2 H, Jˆ6.3 Hz), 5.83 (s, 1 H), 6.60 (br s, 1 H),
6.80–7.90 (m, 13 H), 11.50 (br s, 1 H). dC 48.66, 55.54,
93.96, 113.65, 116.78, 120.46, 122.00, 127.40, 127.64,
128.89, 129.156, 129.37, 131.35, 132.58, 138.26., 153.40,
162.25, 162.61, 188.62. Anal. Calcd for C23H21NO3, MW
359.418: C, 76.86; H, 5.89; N, 3.90%. Found: C, 77.03; H,
5.74; N, 3.84%.
(Z)-3-(2-Hydroxyphenyl)-1-(4-methoxyphenyl)-3-(methyl-
amino)prop-2-en-1-one (3ab). Oil; nmax (liquid film) 1909,
1709, 1367, 878 cmϪ1. NMR (CDCl3): dH 2.86 (d, 3 H,
Jˆ5.3 Hz), 3.85 (s, 3 H), 5.80 (s, 1 H), 6.40 (br s, 1 H),
6.83–7.83 (m, 8 H), 11.10 (br s, 1 H). dC 31.11, 55.36,
92.87, 113.47, 117.09, 120.71, 122.42, 129.31, 129.48,
131.58, 133.07, 153.72, 162.41, 163.87, 188.56. Anal.
Calcd for C17H17NO3, MW 283.322: C, 72.07; H, 6.05; N,
4.94%. Found: C, 72.20; H, 6.12; N, 4.68%.
(Z)-3-(Benzylamino)-3-(2-hydroxyphenyl)-1-pyridin-4-yl-
prop-2-en-1-one (3cc). Oil; nmax (liquid film) 1596, 1566,
1537, 1413, 1341, 1313, 1148, 1007, 909 cmϪ1. NMR
(CDCl3): dH 4.46 (s, 2 H), 5.78 (s, 1 H), 6.50 (br s, 1 H),
6.80–8.70 (m, 13 H), 11.97 (br s, 1 H). dC 48.88, 93.71,
116.31, 119.83, 119.95, 121.40, 122.07, 127.46, 127.63,
128.74, 129.29, 131.40, 137.44, 147.83, 149.18, 154.25,
166.58, 184.76. Anal. Calcd for C21H18N2O2, MW
330.380: C, 76.34; H, 5.49; N, 8.48%. Found: C, 76.61;
H, 5.77; N, 8.36%.
(Z)-3-(2-Hydroxyphenyl)-3-(methylamino)-1-pyridin-4-
ylprop-2-en-1-one (3ac). Orange oil; nmax (liquid film)
1600, 1580, 1240, 754, 681 cmϪ1. NMR (CDCl3): dH 2.97
(d, 3 H, Jˆ5.3 Hz), 3.41 (br s, 1 H), 5.72 (s, 1 H), 6.82–8.85
(m, 8 H), 11.60 (br d, 1 H, Jˆ5.2 Hz). dC 31.74, 93.58,
117.09, 118.38, 120.73, 129.42, 131.90, 147.62, 150.33,
151.23, 153.88, 166.90, 185.70. Anal. Calcd for
C15H14N2O2, MW 254.284: C, 70.85; H, 5.55; N, 11.02%.
Found: C, 70.92; H, 5.87; N, 10.89%.
Cyclisation of 3-(2-hydroxyphenyl)-3-(amino)-1-phenyl-
prop-2-en-1-ones 3
The enaminoketones 3 obtained from the previous step
(3 mmol) were dissolved in a water/THF/acetic acid solu-
tion in the ratio 2/2/1 (10 cm3) and heated at 40ЊC for 0.5 h.
After this time the mixture was neutralised with saturated
solution of Na2CO3 and extracted with CH2Cl2 (2×30 cm3).
The solution was dried with anhydrous Na2SO4, then filtered
and the solvent evaporated under reduced pressure. The
products obtained were submitted to chromatographic
purification or recrystallised. In all cases a single product
was isolated, in 66–94% yield, which spectral data identi-
fied as a 4H-chromen-4-ylidenamine 4. Prolonged heating
of the mixture (5 h) results only in a little decomposition of
the product to unidentified products.
(Z)-3-(2-Hydroxyphenyl)-3-(isopropylamino)-1-phenyl-
prop-2-en-1-one (3ba). Yellow crystals, mp 136–138ЊC
(CH2Cl2/n-hexane); nmax (Nujol) 2715, 1719, 1382, 1121,
1074, 813, 712 cmϪ1. NMR (CDCl3): dH 1.33 (d, 6 H,
Jˆ6.3 Hz), 3.60 (d hept, 1 H, Jˆ6.3, 9.6 Hz), 5.77 (s, 1
H), 6.60–7.89 (m, 9 H), 11.20 (d, 1 H, Jˆ9.6 Hz). dC
24.04, 47.41, 94.10, 117.22, 121.22, 123.75, 128.17,
129.37, 130.06, 132.00, 133.89, 141.38, 154.50, 162.10,
188.30. Anal. Calcd for C18H19NO2, MW 281.349: C,
76.84; H, 6.81; N, 4.98%. Found: C, 76.57; H, 6.53; N,
5.14%.
(Z)-3-(2-Hydroxyphenyl)-3-(isopropylamino)-1-(4-meth-
oxyphenyl)prop-2-en-1-one (3bb). Oil; nmax (liquid film)
1734, 1567, 1458, 1022, 973, 850, 797 cmϪ1. NMR
(CDCl3): dH 1.19 (d, 6 H, Jˆ6.2 Hz), 3.53 (d hept, 1 H,
Jˆ6.3, 9.8 Hz), 3.84 (s, 3 H), 5.75 (s, 1 H), 6.60 (br s, 1
H), 6.86–7.05 (m, 4 H), 7.20–7.40 (m, 2 H), 7.80–7.90 (m,
2 H), 11.02 (br d, 1 H, Jˆ9.8 Hz). dC 23.87, 46.73, 55.35,
93.32, 113.47, 116.30, 120.33, 122.40, 128.56, 129.04,
130.95, 132.48, 152.91, 161.02, 162.01, 188.25. Anal.
Calcd for C19H21NO3, MW 311.375: C, 73.29; H, 6.80; N,
4.50%. Found: C, 73.54; H, 6.65; N, 4.74%.
N-Methyl-N-(2-phenyl-4H-chromen-4-ylidene)amine (4aa).
Yellow oil; nmax (liquid film) 2854, 1636, 1221, 984, 762,
689 cmϪ1. NMR (CDCl3): dH 3.38 (s, 3 H), 6.75 (s, 1 H),
7.20–7.40 (m, 2 H), 7.42–7.63 (m, 4 H), 7.80–8.00 (m, 2
H), 8.18–8.22 (m, 1 H). dC 38.15, 95.54, 118.02, 124.57,
125.27, 126.33, 129.25, 130.98, 131.43, 133.57, 134.50,
153.50, 154.00, 157.50; m/z 235 (Mϩ, 68), 234 (100); 206
(13); 105 (12); 77 (13). Anal. Calcd for C16H13NO, MW
235.281: C, 81.68; H, 5.57; N, 5.95%. Found: C, 81.97;
H, 5.76; N, 5.87%.
N-[2-(4-Methoxyphenyl)-4H-chromen-4-ylidene]-N-
methylamine (4ab). Yellow oil; nmax (liquid film)
2896, 1640, 1220, 769, 702 cmϪ1. NMR (CDCl3): dH 3.36
(s, 3 H), 3.87 (s, 3 H), 6.65 (s, 1 H), 6.96–7.01 (m, 2 H),
(Z)-3-(Benzylamino)-3-(2-hydroxyphenyl)-1-phenylprop-
2-en-1-one (3ca). Yellow crystals, mp 174–176ЊC (ethyl
acetate/n-hexane). nmax (Nujol) 1605, 1560, 1352, 1309,

478
C. Cimarelli, G. Palmieri / Tetrahedron 56 (2000) 475–478
7.20–7.50 (m, 3 H), 7.80–7.90 (m, 2 H), 8.20 (d, 1 H,
Jˆ9.4 Hz). dC 37.88, 55.92, 95.17, 114.66, 117.92,
123.44, 124.63, 125.20, 125.89, 127.92, 131.39, 153.54,
154.14, 157.46, 162.03. m/z 265 (Mϩ, 55), 264 (72), 221
(25), 112 (36), 105 (32), 84 (100). Anal. Calcd for
C17H15NO2, MW 265.307: C, 76.96; H, 5.70; N, 5.28%.
Found: C, 76.78; H, 5.87; N, 5.44%.
3.88 (s, 3 H), 4.82 (s, 2 H), 6.72 (s, 1 H), 7.00 (d, 2 H,
Jˆ8.8 Hz), 7.30–7.41 (m, 5 H), 7.47–7.53 (m, 3 H), 7.82
(d, 2 H, Jˆ8.9 Hz), 8.42 (d, 1 H, Jˆ8.1 Hz). dC 53.67,
55.46, 95.33, 114.18, 117.38, 117.78, 124.70, 125.37,
126.47, 127.49, 127.54, 127.67, 128.40, 131.03, 133.18,
141.13, 152.68, 153.24, 161.57. Anal. Calcd for
C23H19NO2, MW 341.402: C, 80.92; H, 5.61; N, 4.10%.
Found: C, 80.82; H, 5.87; N, 4.34%.
N-Methyl-N-(2-pyridin-4-yl-4H-chromen-4-ylidene)amine
(4ac). Red oil; nmax (liquid film) 2898, 1621, 1120, 972,
753, 685 cmϪ1. NMR (CDCl3): dH 3.35 (s, 3 H), 6.81 (s, 1
H), 7.20–8.75 (m, 8 H). dC 30.00, 98.12, 115.55, 119.17,
121.12, 128.33, 128.94, 137.05, 138.22, 152.44, 154.09,
158.64, 164.18. Anal. Calcd for C15H12N2O, MW 236.269:
C, 76.25; H, 5.12; N, 11.86%. Found: C, 76.32; H, 5.27; N,
11.69%.
4H-Benzyl-N-(2-pyridin-4-yl-4H-chromen-4-ylidene)-
methanamine (4cc). Orange crystals, mp 102–104ЊC
(CH2Cl2/n-hexane); nmax (Nujol) 1611, 1573, 1546, 1495,
1325, 1229, 863, 839, 679, 661 cmϪ1. NMR (CDCl3): dH
4.82 (s, 2 H), 6.91 (s, 1 H), 7.26–8.75 (m, 13 H). dC 53.89,
98.37, 117.46, 119.56, 123.61, 124.76, 125.24, 126.66,
127.60, 128.49, 131.46, 140.31, 141.23, 150.54, 152.03,
153.12, 154.52. Anal. Calcd for C21H16N2O, MW 312.365:
C, 80.75; H, 5.16; N, 8.97%. Found: C, 80.52; H, 5.39; N,
8.84%.
N-(2-Phenyl-4H-chromen-4-ylidene)propan-2-amine (4ba).
Yellow oil; nmax (liquid film) 2901 1611, 1498, 1231, 863,
691 cmϪ1. NMR (CDCl3): dH 1.31 (d, 6 H, Jˆ6.3 Hz), 4.00
(hept, 1 H, Jˆ6.3 Hz), 6.75 (s, 1 H), 7.26–7.85 (m, 9 H). dC
23.71, 49.29, 96.38, 117.38, 121.58, 124.31, 124.84, 125.88,
128.79, 130.54, 131.13, 132.28, 146.12, 151.24, 157.06.
Anal. Calcd for C18H17NO, MW 263.334: C, 82.10; H,
6.51; N, 5.32%. Found: C, 82.36; H, 6.74; N, 5.23%.
Acknowledgements
`
Financial support from the Ministero dell’Universita e della
Ricerca Scientifica e Tecnologica, Rome, and the University
of Camerino (National Project “Stereoselezione in Sintesi
Organica Metodologie ed applicazioni”) are gratefully
aknowledged.
N-[2-(4-Methoxyphenyl)-4H-chromen-4-ylidene]propan-
2-amine (4bb). Yellow crystals, mp 86–88ЊC (CH2Cl2/n-
hexane); nmax (Nujol) 1968, 1608, 1510, 1218, 1116, 830,
790, 664 cmϪ1. NMR (CDCl3): dH 1.30 (d, 6 H, Jˆ3.1 Hz),
3.88 (s, 3 H), 3.70–4.10 (m, 1 H), 6.65 (s, 1 H), 6.95–8.40
(m, 8 H). dC 24.30, 50.00, 56.30, 96.00, 115.37, 117.42,
118.49, 124.19, 127.20, 127.58, 128.73, 146.03, 151.04,
154.00, 156.80, 162.15. Anal. Calcd for C19H19NO2, MW
293.360: C, 77.79; H, 6.53; N, 4.77%. Found: C, 77.91; H,
6.70; N, 4.54%.
References
1. Katritzky, A. R.; Rees, C. W. Comprehensive Heterocyclic
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K.; Tsvetkova, I. D. Chem. Heterocycl. Compd. Engl. Transl. 1972,
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4. Zagorevskii, V. A.; Tsvetkova, I. D.; Orlova, E. K. Chem.
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5. (a) Luche, J. L. J. Am. Chem. Soc. 1978, 100, 2226. (b) Gemal,
A. L.; Luche, J. L. J. Am. Chem. Soc. 1981, 103, 5454.
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(b) Pearson, R. G. J. Am. Chem. Soc. 1963, 85, 3533.
7. (a) Cimarelli, C.; Palmieri, G. Tetrahedron 1998, 54 (51),
15 711. (b) Palmieri, G. Eur. J. Org. Chem. 1999, 805.
N-Benzyl-N-(2-phenyl-4H-chromen-4-ylidene)amine (4ca).
Yellow crystals, mp 94–96ЊC (CH2Cl2/n-hexane). nmax
(Nujol) 1633, 1575, 1412, 1349, 1072, 821, 760 cmϪ1
.
NMR (CDCl3): dH 4.83 (s, 2 H), 6.82 (s, 1 H), 7.20–8.50
(m, 14 H). dC 53.98, 96.50, 117.50, 124.71, 124.82, 125.59,
125.92, 126.50, 127.13, 127.65, 128.40, 128.80, 130.59,
131.14, 133.06, 141.00, 152.63, 153.26. Anal. Calcd for
C19H19NO2, MW 311.377: C, 84.86; H, 5.50; N, 4.50%.
Found: C, 84.92; H, 5.32; N, 4.46%.
N-Benzyl-N-[2-(4-methoxyphenyl)-4H-chromen-4-ylidene]-
amine (4cb). Yellow crystals, mp 132–133ЊC (CH2Cl2/n-
hexane); nmax (Nujol) 1630, 1608, 1572, 1288, 1179, 1077,
983, 958, 917, 902, 874, 855, 818 cmϪ1. NMR (CDCl3): dH