derivative 2i are 0.66 and 1.03, respectively, while the corresponding value for ortho proton of benzene is 0.95.
Obviously it is due to the smaller delocalization of C=C bonds caused by the influence of the pyridine moiety.
The substituents in an indeno unit influence the values of spin-spin coupling constants of the neighboring
protons; besides, ortho and meta couplings are more affected, resembling that of other aromatic systems [3].
The chemical transformations of 6- and 9-nitroindenopyridines 2a and 3a also confirms the structures
determined. Both nitro compounds 2a and 3a can be reduced into amino derivatives 4, 5 and converted into the
corresponding chloroacetoamides 6, 7, but only the 9-substituted compound 7 is capable of intramolecular
alkylation upon treatment with NaH/THF to afford 7a, 10-di-azacyclohepta[def]fluorene 8.
EXPERIMENTAL
1H NMR spectra were recorded on a Bruker AM-360 (360 MHz) in DMSO-d6 solutions using TMS as
internal standard. 2D proton NOE spectra were obtained using standard pulse sequences and data processing
procedures: 1.5 kHz spectral width, 512 or 1024 data points, 128 or 256 t1 increments and 3s relaxation delay.
Simulations of indeno moiety proton shifts were calculated using the PANIC program. Melting points were
determined on a Boetius table.
4-Aryl-5-oxo-4,5-dihydroindeno[1,2-b]pyridines 2,3 (General Method). Ethyl β-aminocrotonate (2.8
mmol) was added to a boiling solution of arylideneindane-1,3-dione 1 (2.5 mmol) in acetic acid (15 ml). The
reaction mixture refluxed for 3-5 min was cooled and diluted with water. A red colored mixture of
dihydroindenopyridine isomers was filtered off, dried, and chromatographed (Silasorb 30 µ, 50×460 mm,
CHCl3−EtOAc, 5:1, flow 30-35 ml/min for separation of 6- and 9-substituted pyridines 2a-h and 3a-h and
15-18 ml/min for 7- and 8-substituted compounds 2i-r and 3i-r). Yields and mp of the compounds obtained are
summarized in Table 1, 1H NMR data − in Tables 2 and 3.
6-Amino- and 9-Amino-3-ethoxycarbonyl-2-methyl-4-phenyl-5-oxo-1H-4,5-dihydroindeno-[1,2-b]pyri-
dines (4, 5). To a solution of nitro compound 2a or 3a (0.2 g, 0.51 mmol) in ethanol (30 ml) 0.4 g of Fe was added
with stirring at 60°C. After addition of 15 ml of acetic acid, the stirring was continued for 3-4 h (TLC checking for
residual nitro compound). The reaction mixture, diluted with water (50 ml) was extracted with chloroform (3×40
ml). The extract, washed with water (3×10 ml), saturated NaHCO3 solution (2×3ml), and dried, was evaporated
and the resulting residue was crystallized from ethanol. 6-Amino isomer 4 scinters at 122-124°C and melts at
233-235°C. 9-Amino isomer 5, mp 200-202°C. See 1H NMR data in Table 2.
6- and 9-(Chloroacetylamino)-3-ethoxycarbonyl-2-methyl-4-phenyl-5-oxo-4,5-dihydroindeno-
pyridine (6, 7). To a solution of amino compound 4 or 5 (0.16 g, 0.45 mmol) in chloroform (12 ml for 7 or
40 ml for 6) triethylamine (0.07 ml) and chloroacetylchloride (0.04 ml) were added sequentially. The reaction
mixture was stirred at room temperature for 4 h. The solvent was evaporated; the residue was triturated with
water and the formed solid afforded chloroacetyl derivatives 6 and 7 after recrystallization from ethanol.
1
6-(Chloroacetylamino)indenopyridine 6. Mp 225−227°C. H NMR spectrum, δ, ppm (J, Hz): 1.09
(3H, t, J = 7.1, CH2CH3); 2.46 (3H, s, 2-CH3); 3.99 (2H, q, J = 7.1, CH2CH3); 4.39 (2H, s, CH2Cl); 4.82 (1H, s,
H-4); 7.06-7.39 (9H, m, aromatic protons); 8.54 (1H, s, H-1); 10.21 (1H, s, NHCO). Found, %: C 65.77; H 4.89;
N 6.30. C24H21ClN2O4. Calculated, %: C 65.98; H 4.84; N 6.41.
9-(Chloroacetylamino)indenopyridine 7. Mp 112-114°C. 1H NMR spectrum, δ, ppm (J, Hz): 1.06 (3H,
t, J = 7.1, CH2CH3); 2.40 (3H, s, 2-CH3); 3.92 (2H, q, J = 7.1, CH2CH3); 4.36 (2H, s, CH2Cl); 4.72 (1H, s, H-4);
7.16 (5H, s, 4-C6H5); 7.36 (2H, m) and 8.11 (2H, m) protons at C(6)−C(9); 10.17 (1H, s, NHCO); 10.33 (1H, s,
H-1). Found, %: C 65.77; H 4.89; N 6.30. C24H21ClN2O4. Calculated, %: C 65.98; H 4.84; N 6.41.
Ethyl 7-methyl-4,9-dioxo-5-phenyl-4,5,7a,8,9,10-hexahydro-7a,10-diaza-cyclo- hepta[def]fluorene-
6-carboxylate (8). To a solution of 9-chloroacetylamino compound 7 (0.15 g, 0.34 mmol) in THF 0.02 g of NaH
(0.5 mmol, 60 % suspension in oil) was added. The reaction mixture, stirred for 2 h, was diluted with 5 ml
41