Synthesis of a new tetracyclic condensed system: 7,8-Dihydro-6H-furo[2′,3′:1,2]cyclohepta[c]isoquinolin-8-one [6]

Full text of DOI:10.1023/A:1011946203286

Chemistry of Heterocyclic Compounds, Vol. 37, No. 6, 2001
SYNTHESIS OF A NEW TETRACYCLIC
CONDENSED SYSTEM: 7,8-DIHYDRO-
6H-FURO[2',3':1,2]CYCLOHEPTA-
c
[ ]ISOQUINOLIN-8-ONE
V. T. Abaev1, A. A. Osipova1, and A. V. Butin2
Keywords: arylmethane, isoquinolinone, furan, furylmethane, recyclization.
Furyl(aryl)methanes, containing a functional group in the ortho position of the aromatic ring, are an
excellent source of benzannelated heterocycles. Thus carbazoles [1], indoles [2, 3], benzofurans [4], and
cinnolines [5] have been obtained as a result of recyclization of the furan ring from the corresponding
furyl(aryl)methanes.
Continuing our studies in this direction, by acid condensation of ortho-formylbenzoic acid and sylvan
we obtained difuryl(aryl)methane (1), which was converted to the amide 2 on reaction with benzylamine.
Ph
O
NH
COOH
COOH
+
O
O
CHO
O
O
O
2
1
Ph
O
O
Ph
N
N 7
O
6
5
O
1
O
4
2
3
3
4
When boiled in an ethanol solution of hydrogen chloride, the 2-hydroxyarylfurylmethanes and
2-(tosylamino)arylfurylmethanes undergo recyclization and are converted respectively to benzofurans [6, 7] and
indoles [3]. With the goal of obtaining the ketone 3, we treated compound 2 under similar conditions but did not
__________________________________________________________________________________________
1
2
North Ossetian State University, Vladikavkaz 362025, Russia; e-mail: abaev@nosu.ru. Kuban State
Technological University, Krasnodar 350072, Russia; e-mail: nemol@kubstu.ru. Translated from Khimiya
Geterotsiklicheskikh Soedinenii, No. 6, pp. 849-850, June, 2001. Original article submitted February 26, 2001.
0009-3122/01/3706-0785$25.00©2001 Plenum Publishing Corporation
785

achieve the desired result. The reaction does not stop in the stage of formation of isoquinoline 3, but rather is
accompanied by intramolecular cyclization and leads to the tetracyclic condensed system 4, the structure of
which has been confirmed by X-ray diffraction.
2-Bis(2-furyl-5-methyl)methylbenzoic Acid (1). 70% Perchloric acid (2 ml) was added to a solution of
o-formylbenzoic acid (25 g, 0.17 mol) and sylvan (33 ml, 0.37 mol) in dioxane (50 ml), and allowed to stand
overnight. The reaction mixture was poured into water (300 ml), the crystallized oil was fitered out, washed
with water, and dried in air. Yield 27 g (54.8%); mp 145-146°C (benzene). IR spectrum (KBr), , cm-1: 2900
ν
1
(OH), 1700 (C=O). H NMR spectrum (200 MHz, CDCl3), , ppm, J (Hz): 2.22 (6H, s, Me); 5.86 (2H, d,
δ
J = 3.2, 3-HFur); 5.89 (2H, d, J = 3.2, 4-HFur); 6.68 (1H, s, CH); 7.30-7.39 (2H, m, HAr); 7.47-7.58 (1H, m, HAr);
8.03-8.12 (1H, m, HAr). Found, %: C 73.15; H 5.79; m/z = 296 [M]+. C18H16O4. Calculated, %: C 72.96; H 5.44.
N-Benzyl-2-[bis(2-furyl-5-methyl)methyl]benzamide (2). A solution of compound 1 (3.0 g, 10 mmol)
in benzylamine (10 ml) was boiled under an air condenser for 24 h, cooled, and poured into a solution of 10%
hydrochloric acid. The oily layer was extracted with benzene. The benzene layer was dried with anhydrous
CaCl2, filtered through a layer of silica gel, evaporated down, and allowed to stand to crystallize. Yield 3.0 g
1
(76.9%); mp 97-98°C (benzene). IR spectrum (KBr), , cm-1: 3260 (NH), 1680 (C=O). H NMR spectrum
ν
(200 MHz, CDCl3), , ppm, J (Hz): 2.20 (6H, s, Me); 4.57 (2H, d, J = 5.4, CH2); 5.83 (4H, s, HFur); 5.97 (1H, s,
δ
CH); 6.14 (1H, t, J = 5.4, NH); 7.20-7.51 (9H, m, HAr). Found, %: C 78.13; H 6.24; N 3.51; m/z = 385 [M]+.
C25H23NO3. Calculated, %: C 77.90; H 6.01; N 3.63.
c
A solution
7-Benzyl-2,4-dimethyl-7,8-dihydro-6H-furo[2',3':1,2]cyclohepta[ ]isoquinolin-8-one (4).
of compound 2 (3.0 g, 7.8 mmol) in a 10 N solution of hydrogen chloride in ethanol (10 ml) was boiled for
30 min until a precipitate fell out of solution. The reaction mixture was cooled, the product was filtered off and
recrystallized from 2-propanol. Yield 2 g (70%); mp 197-198°C. IR spectrum (KBr), , cm-1: 1680 (C=O).
ν
1H NMR spectrum (200 MHz, CDCl3), , ppm, J (Hz): 1.95 (3H, s, Me); 2.23-2.38 (1H, br. m, CH2); 2.50 (3H,
δ
s, Me); 3.47-3.52 (1H, br. m, CH2); 4.82-4.96 (1H, br. m, CH); 5.42-5.81 (1H, br. m, CH2Ph); 6.26 (1H, s, HFur);
7.18-7.48 (5H, m, HPh); 7.44-7.55 (1H, m, HAr); 7.66-7.78 (1H, m, HAr); 8.42-8.49 (1H, m, HAr); 8.51-8.58 (1H,
m, HAr). Found, %: C 81.53; H 5.89; N 4.01; m/z = 367 [M]+. C25H21NO2. Calculated, %: C 81.72; H 5.76;
N 3.81.
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