A new procedure for fusion of a five-membered ring. Building up of the naphtho[1,8-bc]furan system

Article abstract of DOI:10.1007/s11178-005-0010-8

Reactions of 2,6-di-tert-butylnaphthalene-1,5-diol with aminals derived from aromatic aldehydes afforded 2-aryl-4,8-di-tert-butyl-2H-naphtho[1,8-bc] furan-5-ols and 2-aryl-4,8-di-tert-butylnaphtho[1,8-bc]-furan-5-ones.

Full text of DOI:10.1007/s11178-005-0010-8

Russian Journal of Organic Chemistry, Vol. 40, No. 9, 2004, pp. 1300–1302. Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 9, 2004,
pp. 1349–1351.
Original Russian Text Copyright © 2004 by Tyurin, Minyaeva, Mezheritskii.
A New Procedure for Fusion of a Five-Membered Ring.
Building up of the Naphtho[1,8-bc]furan System
R. V. Tyurin, L. G. Minyaeva, and V. V. Mezheritskii
Institute of Physical and Organic Chemistry, Rostov State University,
pr. Stachki 194/2, Rostov-on-Don, 344090 Russia
e-mail: mezher@ipoc.rsu.ru
Received April 15, 2003
Abstract—Reactions of 2,6-di-tert-butylnaphthalene-1,5-diol with aminals derived from aromatic aldehydes
afforded 2-aryl-4,8-di-tert-butyl-2H-naphtho[1,8-bc]furan-5-ols and 2-aryl-4,8-di-tert-butylnaphtho[1,8-bc]-
furan-5-ones.
Naphtho[1,8-bc]furans belong to peri-fused hetero-
cycles which are systematically studied in our labora-
tory [1, 2]. The known methods for the synthesis of
naphtho[1,8-bc]furan derivatives are based on trans-
formations of substituents in positions 1 and 8 of
the naphthalene ring or acid-catalyzed carbonylation
at the peri position with respect to already existing
hydroxy group [3].
more morpholine molecule. Had this process been pre-
ceded by deprotonation of the second hydroxy group
(B → C), the final product would be naphtho-
[1,8-bc:4,5-cb]difuran E (Scheme 1) which was not
detected in the reaction mixture.
In fact, both compounds II and III were always
formed; their ratio depended primarily on the nature
and position of substituents in the aryl group of the
aminal, as well as on the reaction conditions (tempera-
ture, contact with atmospheric oxygen, etc.). 2H-Naph-
tho[1,8-bc]furans II having electron-donor substituents
in the aryl group are more stable. This suggests
homolytic rather than ionic (hydride) mechanism of
the oxidation of compounds II.
In the present communication, we propose a novel
procedure for fusion of a five-membered heteroring via
reaction of aminals with naphthalene-1,5-diol deriva-
tives in which positions 2 and 6 are occupied by
substituents preventing ortho substitution. As initial
compound we selected 2,6-di-tert-butylnaphthalene-
1,5-diol which was described in patent [4]. The reac-
tion occurred on fusion of the reactants at 160–170°C
without a solvent. After heating for a short time under
the conditions ensuring a limited contact with atmos-
pheric oxygen, the major products were 4,8-di-tert-
butyl-2H-naphtho[1,8-bc]furan-5-ols IIa–IIc. The
second isolated product was methylenequinone III
which was formed by oxidation of 2H-naphtho[1,8-bc]-
furan II. The transformation of compounds II into III
was confirmed by oxidation of the former with potas-
sium hexacyanoferrate(III).
The structure of compounds II and III was con-
firmed by the spectral data and elemental analyses.
The IR spectra of II contained absorption bands due
to stretching vibrations of the hydroxy group at 3480–
3510 cm–1. The position of that band in combination
1
with the presence in the H NMR spectrum of a signal
at δ 5.3–6.5 ppm (which disappears upon deuteration)
indicates the absence of intramolecular hydrogen bond.
The carbonyl absorption band in the IR spectra of
methylenequinones III is characterized by a reduced
frequency (1630–1640 cm–1) due to electron-donor
effect of the oxygen atom in the five-membered
heteroring and high degree of conjugation between
the naphthalene system and aryl substituent. In the
1H NMR spectra of 2H-naphtho[1,8-bc]furans II we
observed a signal from the 2-H proton (δ ~6.6 ppm);
no such signal was present in the spectra of methylene-
quinones III.
As follows from Scheme 1, the first reaction step
(A → B) requires base catalysis. Aryldimorpholino-
methane ArCH(NR2)2 abstracts proton from the naph-
thalene hydroxy group with liberation of morpholine
molecule. The resulting iminium ion ArCH=N+R2)
attacks para position (C4) of ambident naphtholate ion
A. The next step is heterocyclization (B → II) with
closure of five-membered ring and elimination of one
1070-4280/04/4009-1300 © 2004 MAIK “Nauka/Interperiodica”

A NEW PROCEDURE FOR FUSION OF A FIVE-MEMBERED RING.
1301
Scheme 1.
OH
OH
OH
CH(Ar)NR2
t-Bu
t-Bu
t-Bu
ArCH(NR2)2
–HNR2
ArCHNR2
Bu-t
Bu-t
Bu-t
OH
O–
OH
I
A
B
H
Ar
O
O
Ar
t-Bu
t-Bu
[O]
–HNR2
Bu-t
Bu-t
OH
O
IIa–IIc
IIIa–IIId
H
O–
CH(Ar)NR2
OH
CH(Ar)NR2
O
Ar
t-Bu
t-Bu
t-Bu
–HNR2
Bu-t
Bu-t
Bu-t
H
OH
OH
NR2
O
Ar
Ar
C
D
E
Ar = Ph (a), 4-MeOC6H4 (b), 3,4-(MeO)2C6H3 (c), 4-BrC6H4 (d); R2N = morpholino.
(1H, Hnaphth), 7.93–7.96 d (1H, Hnaphth, J = 7.91 Hz),
8.0–8.4 d (2H, Hbenz, J = 7.14 Hz). Found, %: C 83.65;
H 7.03. C25H26O2. Calculated, %: C 83.8; H 7.26. The
mother liquor was evaporated, and the residue was
recrystallized from acetonitrile. Yield of 4,8-di-tert-
butyl-2-phenyl-2H-naphtho[1,8-bc]furan-5-ol (IIa)
0.04 g (22 %); colorless substance, mp 165–166°C.
IR spectrum, ν cm–1: 3510 (OH). Found, %: C 83.56;
H 7.77. C26H30O3. Calculated, %: C 83.3; H 7.78.
EXPERIMENTAL
The IR spectra were recorded on a Specord IR-71
instrument from samples dispersed in mineral oil. The
1H NMR spectra were measured on Varian Unity-300
and Bruker Avance DPX-250 spectrometers using
HMDS as internal reference and CDCl3 or CD3CN as
solvent. The purity of the products was checked by
thin-layer chromatography on aluminum oxide with
chloroform as eluent.
b. With 4-methoxyphenyldimorpholinomethane.
A mixture of 0.068 g (0.25 mmol) of compound I and
0.109 g (0.375 mmol) of 4-methoxyphenyldimorpho-
linomethane was heated for 10 min at 160–170°C,
cooled, and recrystallized from 2 ml of ethanol. Yield
of 4,8-di-tert-butyl-2-(4-methoxyphenyl)-5H-naphtho-
[1,8-bc]furan-5-one (IIIb) 0.02 g (20.6%); bright yel-
low substance, mp 262–263°C. IR spectrum, ν, cm–1:
Reaction of 2,6-di-tert-butylnaphthalene-1,5-diol
(I) with aryldimorpholinomethanes. a. With di-
morpholino(phenyl)methane. A mixture of 0.136 g
(0.5 mmol) of compound I and 0.4 g of dimorpholino-
(phenyl)methane was heated for 10 min at 160–170°C,
cooled, and recrystallized from 2 ml of ethanol. Yield
of 4,8-di-tert-butyl-2-phenyl-5H-naphtho[1,8-bc]-
furan-5-one (IIIa) 0.09 g (51%); bright yellow sub-
stance, mp 193–194°C (from alcohol). IR spectrum, ν,
1
1633 (C=O). H NMR spectrum (CD3CN), δ, ppm:
1.28 s (9H, t-Bu), 1.62 s (9H, t-Bu), 3.88 s (3H,
OCH3), 7.0–7.96 m (4H, Hbenz), 7.42–7.86 m (3H,
Hnaphth). Found, %: C 80.21; H 7.43. C26H28O3. Calcu-
lated, %: C 80.41; H 7.22. The mother liquor was
evaporated, and the residue was recrystallized from
1
cm–1: 1633 (C=O). H NMR spectrum (CDCl3), δ,
ppm: 1.4 s (9H, t-Bu), 1.6 s (9H, t-Bu), 7.42–7.46 d
(1H, Hnaphth, J = 8.02 Hz ), 7.46–7.52 t (1H, Hbenz, J =
7.15 Hz), 7.54–7.6 t (2H, Hbenz, J = 7.91 Hz), 7.9 s
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 9 2004

TYURIN et al.
1302
acetonitrile. Yield of 4,8-di-tert-butyl-2-(4-methoxy-
phenyl)-2H-naphtho[1,8-bc]furan-5-ol (IIb) 0.045 g
(46.2%); colorless substance, mp 185–186°C. IR spec-
trum, ν, cm–1: 3487 (OH). 1H NMR spectrum
(CD3CN), δ, ppm: 1.42 s (9H, t-Bu), 1.44 s (9H, t-Bu),
3.75 s (3H, OCH3), 6,51 s (1H, OH), 6.64 s (1H,
CHfuran, J = 1.11 Hz), 6.68–6.74 d (2H, Hbenz, J =
8.8 Hz), 6.97–7.01 d (1H, Hnaphth, J = 8.72 Hz), 7.16 s
substance, mp 166– 167°C. IR spectrum, ν, cm–1: 1647
(C=O). Found, %: C 68.93; H 5.86. C25H25BrO2. Cal-
culated, %: C 68.65; H 5,72.
Oxidation of 4,8-di-tert-butyl-2-(3,4-dimethoxy-
phenyl)-2H-naphtho[1,8-bc]furan-5-ol (IIc). A solu-
tion of 0.418 g (1.6 mmol) of K3[Fe(CN)6] and 0.075 g
(1.6 mmol) of NaOH in water was added to a solution
of 0.07 g (0.167 mmol) of compound IIc in 2 ml
of benzene, and the mixture was stirred for 1 h. The
organic layer was separated, the solvent was distilled
off under reduced pressure, and the residue was recrys-
tallized from ethanol. Yield of 4,8-di-tert-butyl-2-(3,4-
dimethoxyphenyl)-5H-naphtho[1,8-bc]furan-5-one
(IIIc) 0.066 g (95%); bright yellow substance,
mp 160–161°C. IR spectrum, ν, cm–1: 1633 (C=O).
1H NMR spectrum (CDCl3), δ, ppm: 1.44 s (9H, t-Bu),
1.57 s (9H, t-Bu), 3.95 s (3H, OCH3), 4.1 s (3H,
OCH3), 7.02–7.06 d (1H, Hbenz, J = 8.45 Hz), 7.39–
7.43 d (1H, Hnaphth, J = 8.03 Hz), 7.52 s (1H, Hbenz, J =
1.79 Hz), 7.62–7.66 d (1H, Hbenz, J = 8.48 Hz), 7.87 s
(1H, Hnaphth), 7.91–7.96 d (1H, Hnaphth, J = 8.01 Hz).
Found, %: C 77.31; H 7.56. C26H28O3. Calculated, %:
C 77.51; H 7.18.
(1H, Hnaphth, J = 1.41 Hz), 7.21–7.25 d (2H, Hbenz
,
J = 8.6 Hz), 7.26–7.3 d (1H, Hnaphth, J = 8.75 Hz).
Found, %: C 79.46; H 7.52. C26H30O3. Calculated, %:
C 80.0; H 7.69.
c. With 3,4-dimethoxyphenyldimorpholinomethane.
A mixture of 3 g (11 mmol) of compound I and 7.1 g
(22 mmol) of 3,4-dimethoxyphenyldimorpholino-
methane was heated for 10 min at 160–170°C, cooled,
and recrystallized from ethanol. Yield of 4,8-di-tert-
butyl-2-(3,4-dimethoxyphenyl)-2H-naphtho[1,8-bc]-
furan-5-ol (IIc) 3.75 g (81%), mp 221–222°C. IR
1
spectrum, ν, cm–1: 3499 (OH). H NMR spectrum
(CDCl3), δ, ppm: 1.43 s (9H, t-Bu), 1.45 s (9H, t-Bu),
3.77 s (3H, OCH3), 3.87 s (3H, OCH3), 5,3 s (1H, OH),
6.76 s (1H, CHfuran, J = 1.36 Hz), 6.85 s (1H, Hbenz, J =
1.15 Hz), 6.84–6.88 d (1H, Hbenz, J = 8.37 Hz), 7.16 d
(1H, Hbenz, J = 8,24 Hz), 7.07 s (1H, Hnaphth, J =
1.53 Hz), 7.11–7.15 d (1H, Hnaphth, J = 8.63 Hz), 7.4–
7.44 d (1H, Hnaphth, J = 8.64 Hz). Found, %: C 77.42;
H 7.78. C27H32O4. Calculated, %: C 77.14; H 7.62.
REFERENCES
1. Mezheritskii, V.V., Zhukovskaya, O.N., Tkachenko, V.V.,
and Dorofeenko, G.N., Khim. Geterotsikl. Soedin., 1977,
p. 1693.
d. With 4-bromophenyldimorpholinomethane.
A mixture of 0.136 g (0.5 mmol) of compound I and
0.341 g (1 mmol) of 4-bromophenyldimorpholino-
methane was heated for 10 min at 160–170°C, cooled,
and recrystallized from 2 ml of ethanol. Yield of 2-(4-
bromophenyl)-4,8-di-tert-butyl-5H-naphtho[1,8-bc]-
furan-5-one (IIId) 0.08 g (36.6%); bright yellow
2. Mezheritskii, V.V., Tkachenko, V.V., Zhukovskaya, O.N.,
and Dorofeenko, G.N., Zh. Org. Khim., 1978, vol. 13,
p. 1986.
3. Mezheritskii, V.V. and Tkachenko, V.V., Adv. Hetero-
cycl. Chem., 1990, vol. 51, p. 1
4. US Patent no. 2881219, 1959; Ref. Zh., Khim., 1960,
no. 12P556.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 9 2004