The synthesis of functionalized pyranophenalenones

Article abstract of DOI:10.1007/s00706-008-0082-6

Protonation of the highly reactive 1:1 intermediate produced in the reaction between alkyl or aryl isocyanides and electron-deficient acetylenic esters with 3-hydroxy-1H-phenalene-1-one leads to a vinylisonitrilium cation, which undergoes an addition reac

Full text of DOI:10.1007/s00706-008-0082-6

Monatsh Chem (2009) 140:513–517
DOI 10.1007/s00706-008-0082-6
ORIGINAL PAPER
The synthesis of functionalized pyranophenalenones
Mohammad B. Teimouri Æ Reihaneh Bazhrang
Received: 17 September 2008 / Accepted: 11 October 2008 / Published online: 26 November 2008
ꢀ Springer-Verlag 2008
Abstract Protonation of the highly reactive 1:1 inter-
mediate produced in the reaction between alkyl or aryl
isocyanides and electron-deficient acetylenic esters with
3-hydroxy-1H-phenalene-1-one leads to a vinylisonitrilium
cation, which undergoes an addition reaction with the
conjugate base of the 3-hydroxy-1H-phenalene-1-one
to produce biologically interesting dialkyl 10-(alkyl
or arylamino)-7-oxo-7H,8H-naphtho[1,8-gh]chromene-8,9-
dicarboxylates in moderate to fairly good yields at room
temperature.
and photodynamic [8]. For example, furophenalene deriv-
atives have been reported to have antibiotic and
antimicrobial activities [9]. On the other hand, condensed
heterocyclic compounds containing a 4H-pyrano fragment
are significant in a number of practical applications. Some
have been shown to exhibit different biological activities
[10], such as anticoagulant, spasmolytic, diutretic, anti-
cancer [11], antimalarial, and ganglioblocking action [12],
and antianaphylactin characteristics [13]. 4H-Pyrans also
constitute the structural unit of a series of natural products
[14]. Finally, a number of 2-amino-4H-pyrans are useful as
photoactive materials [15].
Keywords Alkynes ꢀ Heterocycles ꢀ Isocyanide ꢀ
Multicomponent reactions ꢀ Zwitterions
To the best of our knowledge, there is only one report [16]
on the synthesis of fused pyranophenelenones containing the
7H,10H-naphtho[1,8-gh]chromen-7-one skeleton via the
reaction of 3-hydroxy-1H-phenalene-1-one and a,b-unsatu-
rated aldehydes in the presence of indium(III) chloride, and
there is no report on the preparation of condensed pyran-
ophenalenone compounds with 7H,8H-naphtho[1,8-gh]
chromen-7-one structure.
Introduction
Phenalene derivatives are an important class of nonbenz-
enoid aromatic compounds, since many phenalene-
containing natural and synthetic products exhibit diverse
biological activities [1, 2], such as antitumor [3], antibac-
terial [4], nematicidic [5], antifungal [6], phytoalexin [7],
It has been shown that alkyl or aryl isocyanides add
to dialkyl acetylenedicarboxylates to generate zwitter-
ionic species, which serve as intermediates in many
different reactions [17–22]. Recently, these highly reac-
tive zwitterionic intermediates have been captured by
suitable CH-, OH-, and NH-acid substrates, such as
tetronic acid [20], benzoic acids [21], and phthalhyd-
razide [22], which produced 4H-furo[3,4-b]pyrans,
butenedioates and 1H-pyrazolo[1,2-b]phthalazine-5,10-
dione derivatives.
M. B. Teimouri (&)
Petrochemical Department,
Iran Polymer and Petrochemical Institute,
P.O. Box 14965-115, Tehran, Iran
e-mail: m.teimouri@ippi.ac.ir
In our continuous quest aimed toward developing bio-
logically active heterocyclic synthesis via isocyanide-based
multicomponent reactions involving CH-, NH-, or OH-
acids [22–27], in this report the facile synthesis of some
new pyranophenalenone heterocycles is described.
R. Bazhrang
Department of Chemistry,
Payame Noor University of Abhar,
Abhar, Zanjan, Iran
123

514
M. B. Teimouri, R. Bazhrang
Scheme 1
OR'
CO2R'
O
O
HO
CO2R'
Acetone
rt, 48 h
O
H
+
+
C
R
N
N
R
O
4
CO2R'
1
3
2
R'
R'
R
Yield/%
R
4a
Methyl
Methyl
Methyl
Methyl
Methyl
Ethyl
Ethyl
Ethyl
Ethyl
Ethyl
1a
61
58
63
55
60
67
65
70
73
59
Cyclohexyl
Cyclohexyl
2a Methyl
Ethyl
4b tert-Butyl
4c
1b tert-Butyl
1c
2b
tert-Octyl
Benzyl
2,6-Dimethylphenyl
Cyclohexyl
tert-Butyl
tert-Octyl
Benzyl
2,6-Dimethylphenyl
tert-Octyl
Benzyl
2,6-Dimethylphenyl
4d
4e
4f
4g
4h
4i
1d
1e
4j
Results and discussion
that is attached to a chiral moiety could show a chiral
behavior. Therefore, observing six distinct carbon reso-
nances for six carbons of cyclohexyl ring of compound 4a
is not surprising. The 1H decoupled 13C NMR spectrum of
4a showed 26 distinct resonances in agreement with the
suggested structure. The structural assignments made on
the basis of the 1H and 13C NMR spectra of compounds 4a
were supported by measurement of its IR spectra. The IR
spectrum of 4a showed strong absorptions at 1,758, 1,733,
and 1,712 cm-1 due to the carbonyls and the amino group
The one-pot three-component condensation reactions of
isocyanides 1 with dialkyl acetylenedicarboxylates 2 in the
presence of 3-hydroxy-1H-phenalene-1-one (3) proceeded
spontaneously at room temperature in acetone and were
complete after 48 h to afford dialkyl 10-(alkylamino)-7-
oxo-7H,8H-naphtho[1,8-gh]chromene-8,9-dicarboxylates
4, in moderate to good yields (Scheme 1). The one-pot
three-component condensation reactions were carried out
by first mixing isocyanide 1 and 3-hydroxy-1H-phenalene-
1-one (3) in dry acetone. Then, a solution of acetylenic
ester 2 in dry acetone was added to the reaction mixture.
The 1H and 13C NMR spectra of the crude products clearly
indicated the formation of fused pyranophenalenone 4. Any
product other than 4 could not be detected by NMR
spectroscopy.
1
at 3,250 cm-1 as a weak broad band. The H decoupled
13C NMR spectra of 4b-4j are similar to those of 4a except
for the R or R0 groups, which exhibit characteristic signals
with appropriate chemical shifts.
The scope and limitations of this simple process were
explored by using two dialkyl acetylenedicarboxylates
and five alkyl or aryl isocyanides. We have found that
the reaction proceeds efficiently even with hindered alkyl
or aryl isocyanides. However, the mechanism of this
reaction has not been established experimentally; a likely
mechanism for the formation of these heterocycles 4 is
shown in Scheme 2. In the first step, nucleophilic attack
of the isocyanide to the acetylenic ester and subsequent
protonation of the highly reactive 1:1 zwitterionic inter-
mediate by strong CH-acid (3-hydroxy-1H-phenalene-
1-one) afford the vinylisonitrilium cation 5. Then, the
vinylisonitrilium cation 5 could have undergone addition
reactions with the nitrogen atom of the conjugate base of
the CH-acid 6 on two possible electrophilic sites (1,2-
addition and 1,4-conjugate addition) to produce two
possible intermediates 7 and 8 in equilibrium with each
other. These intermediates can be cyclized under the
reaction conditions employed to produce the dialkyl
10-(alkylamino)-7-oxo-7H,8H-naphtho[1,8-gh]chromene-8,
9-dicarboxylates 4.
The elucidation of the structure of 4 using H and 13C
1
NMR spectroscopic data is discussed with 4a as an
example. The 1H NMR spectrum of 4a consisted of
multiplet signals for the cyclohexyl ring protons (dH 1.33–
2.12 ppm) and the NH-CH resonance (dH 3.93 ppm) and
three sharp singlets for two methoxy groups (dH 3.66 and
3.75 ppm) and the allylic methine (d 4.93 ppm). A doublet
resonance (dH 8.70 ppm) was observed for the NH group.
The presence of amine proton was confirmed by exchange
with D2O labile proton. The chemical shift of NH group
indicates that this moiety must have participated in a six-
membered intramolecular hydrogen bond formation with
the vicinal carbonyl group as shown in Scheme 1. The
aromatic hydrogens give rise to multiplet signals in the
aromatic region of the spectrum.
The 4H-pyran moiety in compound 4a has an asym-
metric carbon atom bearing a hydrogen atom. In fact, these
products 4a–4j are chiral molecules. As a result, the group
123

The synthesis of functionalized pyranophenalenones
515
O
O
CO2R'
HO
O
CO2R'
CH
C
R
N
C
+
+
R
N
C
C
C
CO2R'
CO2R'
6
5
1,4-conjugate addition
1,2-addition
CO2R'
CO2R'
O
O
CO2R'
CO2R'
O
NR
O
NR
7
8
O
CO2R'
OR'
O
H
O
N
R
4
Scheme 2
In conclusion, the three-component reactions of alkyl or
aryl isocyanides, dialkyl acetylenedicarboxylates, and 3-
hydroxy-1H-phenalene-1-one were achieved under mild
conditions, providing a convenient method for the syn-
thesis of dialkyl 10-(alkyl or arylamino)-7-oxo-7H,8H-
naphtho[1,8-gh]chromene-8,9-dicarboxylates. Using this
method, a series of novel biologically interesting pyran-
ophenalenones were synthesized from easily commercially
available starting materials for the first time.
obtained from Aldrich chemical company. All reagents
were used without further purification.
Typical procedure for the preparation of 4a
To a magnetically stirred solution of 0.081 g 3-hydroxy-
1H-phenalene-1-one (0.5 mmol) and 0.055 g cyclohexyl
isocyanide (0.5 mmol) in 40 cm3 dry acetone was added
dropwise a mixture of 0.071 g dimethyl acetylenedicar-
boxylate (0.5 mmol) in 2 cm3 acetone at room temperature
(25 ꢁC) over 10 min via a syringe. The reaction mixture
was stirred at room temperature for 48 h. The solvent was
removed under reduced pressure, and the solid residue
was washed with diethyl ether and crystallized from
CH2Cl2:n-hexane (1:2) to give 0.137 g 4a as yellow crystals
(61%).
Experimental
Melting points were measured on a Bu¨chi 535 apparatus.
Elemental analyses (C, H, N) were conducted using the
Heraeus CHN-O-Rapid analyzer; their results were found
to be in good agreement ( 0.2%) with the calculated
values. FT-IR Spectra were recorded on a Bruker Equinox-
rac-Dimethyl 10-(cyclohexylamino)-7-oxo-7H,8H-
naphtho[1,8-gh]chromene-8,9-dicarboxylates
(4a, C26H25NO6)
1
55 spectrometer. H and 13C NMR spectra were recorded
on a Bruker DRX-400 Avance spectrometer at 400.13 and
100.77 MHz, with CDCl3 as solvent. The solvents, dime-
thyl and diethyl acetylenedicarboxylates, cyclohexyl and
1,1,3,3-tetramethylbutyl (tert-octyl) isocyanides used in
this work were purchased from Merck, and the tert-butyl
isocyanide and 2,6-dimethylphenyl isocyanide were
obtained from Fluka (Buchs, Switzerland). The benzyl
isocyanide and 3-hydroxy-1H-phenalene-1-one were
Mp 193–195 ꢁC (dec.); IR (KBr): m ¼ 3; 250 (N–H), 1,758,
1
1,733, 1,712 (C=O) cm-1; H NMR (CDCl3, 400.1 MHz):
d = 1.33–2.12 (m, 5 CH2), 3.66 and 3.75 (2 s, 2 OCH3),
3.93 (m, NHCH), 4.93 (s, NCH), 7.64–8.62 (m, arom.),
3
8.70 (d, JHH = 7.0 Hz, NH…O=C) ppm; 13C NMR
(CDCl3, 100.7 MHz): d = 182.7, 173.7, 169.8, 159.1,
155.0, 134.9, 132.7, 131.9, 130.6, 128.2, 127.2, 126.3,
123

516
M. B. Teimouri, R. Bazhrang
126.2, 125.8, 122.3, 114.5, 72.6, 52.4, 51.1, 50.6, 35.6,
33.9, 33.5, 25.5, 24.6, 24.5 ppm.
rac-Diethyl 10-(cyclohexylamino)-7-oxo-7H,8H-
naphtho[1,8-gh]chromene-8,9-dicarboxylates
(4f, C28H29NO6)
rac-Dimethyl 10-(tert-butylamino)-7-oxo-7H,8H-
naphtho[1,8-gh]chromene-8,9-dicarboxylates
(4b, C24H23NO6)
Yellow powder (0.160 g, 67%); mp 190–192 ꢁC (dec.); IR
(KBr): m ¼ 3; 268 (N–H), 1,760, 1,744, 1,710 (C=O) cm-1
;
1H NMR (CDCl3, 400.1 MHz): d = 1.23 and 1.30 (2 t,
3JHH = 7.1 Hz, 2 OCH2CH3), 1.31–2.11 (m, 5 CH2), 4.11–
4.22 (m, 2 OCH2CH3), 4.96 (s, NCH), 7.67–8.63 (m,
Yellow powder (0.123 g, 58%); mp 167–169 ꢁC (dec.); IR
(KBr): m ¼ 3; 256 (N–H), 1,760, 1,726, 1,711 (C=O) cm-1
;
1H NMR (CDCl3, 400.1 MHz): d = 1.61 (s, CMe3), 3.67
and 3.74 (2 s, 2 OCH3), 4.94 (s, NCH), 7.60–8.63 (m,
arom.), 9.00 (br s, NH…O=C) ppm; 13C NMR (CDCl3,
100.7 MHz): d = 182.8, 173.7, 169.7, 159.0, 154.9, 135.0,
132.8, 131.9, 130.6, 128.1, 127.2, 126.3, 126.2, 125.7,
122.3, 114.4, 72.6, 52.6, 52.4, 51.6, 51.2, 30.7 ppm.
3
arom.), 9.00 (d, JHH = 7.0 Hz, NH…O=C) ppm; 13C
NMR (CDCl3, 100.7 MHz): d = 182.7, 173.6, 169.8,
159.1, 155.0, 135.0, 132.8, 132.0, 130.6, 128.2, 127.2,
126.3, 126.2, 125.8, 122.4, 114.4, 72.9, 62.2, 61.4, 51.3,
35.6, 33.9, 33.5, 25.5, 24.6, 24.5, 14.1, 13.9 ppm.
rac-Diethyl 10-(tert-butylamino)-7-oxo-7H,8H-
naphtho[1,8-gh]chromene-8,9-dicarboxylates
(4g, C26H27NO6)
rac-Dimethyl 10-(1,1,3,3-tetramethylbutylamino)-7-
oxo-7H,8H-naphtho[1,8-gh]chromene-8,9-dicarboxylates
(4c, C28H31NO6)
Yellow powder (0.146 g, 65%); mp 167–169 ꢁC (dec.); IR
Yellow powder (0.150 g, 63%); mp 188–190 ꢁC (dec.); IR
(KBr): m ¼ 3; 300 (N–H), 1,755, 1,728, 1,708 (C=O) cm-1
;
(KBr): m ¼ 3; 266 (N–H), 1,755, 1,735, 1,709 (C=O) cm-1
;
1H NMR (CDCl3, 400.1 MHz): d = 1.23 and 1.32 (2 t,
3JHH = 7.1 Hz, 2 OCH2CH3), 1.58 (s, CMe3), 4.09–4.23
(m, 2 OCH2CH3), 4.94 (s, NCH), 7.68–8.63 (6 H, m,
arom.), 9.05 (br s, NH…O=C) ppm; 13C NMR (CDCl3,
100.7 MHz): d = 182.9, 173.6, 169.6, 160.3, 155.3, 135.0,
132.7, 132.0, 130.5, 128.1, 127.0, 127.2, 126.3, 126.2,
122.4, 114.7, 73.5, 61.0, 59.7, 52.5, 35.5, 30.7, 14.6,
14.2 ppm.
1H NMR (CDCl3, 400.1 MHz): d = 1.00 (s, CMe3), 1.59
and 1.63 (2 s, CMe2), 1.95 (s, CH2), 3.64, 3.75 (2 s, 2
OCH3), 4.97 (s, NCH), 7.67–8.64 (m, arom.), 9.11 (s,
NH…O=C) ppm; 13C NMR (CDCl3, 100.7 MHz):
d = 182.8, 173.7, 170.0, 160.4, 155.3, 135.0, 132.8,
132.0, 130.7, 128.1, 127.2, 126.3, 126.2, 122.3, 114.7,
73.0, 56.2, 53.4, 52.4, 51.1, 35.4, 31.8, 31.7, 31.4,
31.2 ppm.
rac-Diethyl 10-(1,1,3,3-tetramethylbutylamino)-7-
oxo-7H,8H-naphtho[1,8-gh]chromene-8,9-dicarboxylates
(4h, C30H35NO6)
rac-Dimethyl 10-(benzylamino)-7-oxo-7H,8H-
naphtho[1,8-gh]chromene-8,9-dicarboxylates
(4d, C27H21NO6)
Yellow powder (0.177 g, 70%); mp 213–215 ꢁC (dec.); IR
Yellow powder (0.126 g, 55%); mp 153–155 ꢁC (dec.); IR
(KBr): m ¼ 3; 330 (N–H), 1,759, 1,741, 1,710 (C=O) cm-1
;
(KBr): m ¼ 3; 310 (N–H), 1,766, 1,743, 1,712 (C=O) cm-1
;
1H NMR (CDCl3, 400.1 MHz): d = 0.99 (s, CMe3), 1.21
and 1.30 (2 t, JHH = 7.1 Hz, 2 OCH2CH3), 1.60 and 1.62
1H NMR (CDCl3, 400.1 MHz): d = 3.69 and 3.78 (2 s, 2
OCH3), 4.73 and 4.79 (AB-q, JHH = 17.6 Hz, NHCH2),
3
2
(2 s, CMe2), 1.96 (s, CH2), 4.12–4.22 (m, 2 OCH2CH3),
4.94 (s, NCH), 7.65–8.64 (m, arom.), 9.06 (s, NH…O=C)
ppm; 13C NMR (CDCl3, 100.7 MHz): d = 182.8, 173.6,
169.8, 160.4, 155.4, 135.0, 132.6, 132.1, 130.2, 128.0,
127.0, 126.6, 126.2, 122.4, 113.4, 72.6, 54.3, 61.3, 61.2,
51.5, 35.4, 31.8, 31.7, 31.4, 31.2, 14.2, 14.0 ppm.
4.94 (s, NCH), 7.26–8.63 (m, arom.), 9.14 (br s,
NH…O=C) ppm; 13C NMR (CDCl3, 100.7 MHz):
d = 182.9, 171.7, 169.1, 168.5, 158.9, 136.7, 134.9,
132.6, 131.6, 130.5, 128.9, 128.7, 128.4, 127.5, 127.2,
126.7, 126.6, 126.2, 126.1, 116.4, 54.3, 52.1, 51.2, 44.3,
41.2 ppm.
rac-Diethyl 10-(benzylamino)-7-oxo-7H,8H-naphtho
[1,8-gh]chromene-8,9-dicarboxylates (4i, C29H25NO6)
Yellow powder (0.177 g, 73%); mp 173–175 ꢁC (dec.); IR
rac-Dimethyl 10-(2,6-dimethylanilino)-7-oxo-7H,
8H-naphtho[1,8-gh]chromene-8,9-dicarboxylates
(4e, C28H23NO6)
(KBr): m ¼ 3; 310 (N–H), 1,762, 1,738, 1,711 (C=O) cm-1
;
Yellow powder (0.140 g, 60%); mp 195–197 ꢁC (dec.); IR
1H NMR (CDCl3, 400.1 MHz): d = 1.25 and 1.32 (2 t,
3JHH = 7.1 Hz, 2 OCH2CH3), 4.11–4.29 (m, 2 OCH2CH3),
4.75 and 4.81 (AB-q, NHCH2), 4.95 (s, NCH), 7.27–8.62
(m, arom.), 9.05 (br s, NH…O=C) ppm; 13C NMR (CDCl3,
100.7 MHz): d = 182.9, 171.7, 169.1, 168.5, 158.9, 136.8,
134.9, 132.6, 131.7, 130.5, 128.9, 128.7, 128.4, 127.4,
127.2, 126.8, 126.6, 126.2, 126.1, 117.1, 61.7, 61.1, 54.3,
44.2, 41.0, 14.0, 13.9 ppm.
(KBr): m ¼ 3; 336 (N–H), 1,764, 1,740, 1,709 (C=O) cm-1
;
1H NMR (CDCl3, 400.1 MHz): d = 2.19 and 2.42 (2 s,
C6H3Me2), dH 3.67 and 3.72 (2 s, 2 OCH3), 5.01 (s, NCH),
7.09–8.60 (m, arom.), 9.90 (br s, NH…O=C) ppm; 13C
NMR (CDCl3, 100.7 MHz): d = 182.0, 173.2, 169.7,
158.3, 154.9, 136.8, 136.1, 134.9, 134.5, 132.5, 131.6,
130.5, 128.2, 128.0, 127.4, 127.1, 127.0, 126.4, 126.0,
126.0, 121.9, 114.4, 74.6, 52.2, 51.8, 35.8, 18.7, 18.4 ppm.
123

The synthesis of functionalized pyranophenalenones
517
´
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rac-Diethyl 10-(2,6-dimethylanilino)-7-oxo-7H,8H-
naphtho[1,8-gh]chromene-8,9-dicarboxylates
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Yellow powder (0.147 g, 59%); mp 202–204 ꢁC (dec.); IR
(KBr): m ¼ 3; 295 (N–H), 1,770, 1,742, 1,715 (C=O) cm-1
;
1H NMR (CDCl3, 400.1 MHz): d = 1.25 and 1.37 (2 t,
2 OCH2CH3), 2.18 and 2.41 (2 s,
3JHH = 7.1 Hz,
C6H3Me2), 4.12–4.34 (m, 2 OCH2CH3), 5.00 (s, NCH),
7.12–8.61 (m, arom.), 9.88 (br s, NH…O=C) ppm; 13C
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158.3, 155.1, 136.8, 136.1, 134.8, 134.5, 132.5, 131.7,
130.5, 128.2, 128.0, 127.4, 127.1, 126.4, 126.1, 126.0,
122.0, 114.3, 74.5, 61.1, 60.0, 36.0, 18.6, 18.4, 14.5,
14.2 ppm.
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