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Modified coumarins. 29. Synthesis of structural analogs of natural 6-arylfuro[3,2-g]chromen-7-ones

March 2009
Chemistry of Natural Compounds 45(2):158-163

March 2009
45(2):158-163

Authors:

Eximed Laboratory

3-Substituted 6-arylfuro[3,2-g]chromen-7-ones, structural analogs of natural furocoumarins, were synthesized by linear annelation of a furan fragment to a 3-arylcoumarin system.

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158

Chemistry of Natural Compounds, Vol. 45, No. 2, 2009

MODIFIED COUMARINS. 29. SYNTHESIS OF STRUCTURAL

ANALOGS OF NATURAL 6-ARYLFURO[3,2-g]CHROMEN-7-ONES

M. M. Garazd,1* Ya. L. Garazd,2 A. S. Ogorodniichuk,1 and V. P. Khilya2 UDC 547.814.5

3-Substituted 6-arylfuro[3,2-g]chromen-7-ones, structural analogs of natural furocoumarins, were synthesized

by linear annelation of a furan fragment to a 3-arylcoumarin system.

Key words: coumarins, 3-arylcoumarins, furocoumarins, psoralene.

Furocoumarins are structurally varied natural compounds that are mostly derivatives of the linear furocoumarin

psoralene [1]. The heightened interest in furocoumarins is due to the important role that they play in the life processes of

plants and animals and their high and varied biological activity [2]. In most instances furocoumarins are unsubstituted in the

2- and 3-positions of the pyran-2-one ring. However, compounds containing aryl substituents in these positions have been

isolated from natural sources. Examples of such secondary metabolites based on the 3-arylcoumarin core are pachyrrhizin {6-

(6-methoxy-1,3-benzodioxol-5-yl)furo[3,2-g]chromen-7-one}, which was isolated from the plants Pachyrrhizus erosus [3-5],

P. tuberosus [6], Neorautassenia pseudopachyrriza [7], and N. edulis [8-10]; neofolin {9-methoxy-6-(6-methoxy-1,3-

benzodioxol-5-yl)furo[3,2-g]chromen-7-one}, which was isolated from Neorautanenia ficifolia [11]; and 6-(2,4,5-

trimethoxyphenyl)furo[3,2-g]chromen-7-one, which is produced by P. tuberosus [6].

We synthesized substituted 6-arylfuro[3,2-g]chromen-7-ones, structural analogs of natural furocoumarins, based on

the 3-arylcoumarin core.

7-Acetoxycoumarins 1-5 were prepared by a Perkin—Oglialoro reaction [12] of 2,4-dihydroxybenzaldehyde and

substituted phenylacetic acids in acetic anhydride in the presence of pyridine. Acidolysis of 1-5 formed 7-hydroxy-3-

arylcoumarins 6-10 that were required for further transformations.

The reaction of hydroxycoumarins 6-10 with

-haloketones under Williamson conditions produced the corresponding

substituted oxoethers 11-24. The alkylating agents in these syntheses were chloroacetone (11-15), 1-chloropinacolone (16-

18), phenacylbromide (19 and 20), 4-methylphenacylbromide (21), 4-fluorophenacylchloride (22), and 3-methoxy-

phenacylbromide (23 and 24).

1) Institute of Bioorganic and Petroleum Chemistry, National Academy of Sciences of Ukraine, 02094, Ukraine,

Kiev, ul. Murmanskaya, 1, e-mail: gmm@i.com.ua; 1) Taras Shevchenko Kiev National University, 01033, Ukraine, Kiev, ul.

Vladimirskaya, 64. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 140-144, March-April, 2009. Original article

submitted November 6, 2007.

a. EtOH, H2SO4; b. R3COCH2Hal, K2CO3; c. 1. NaOH, 2. H2SO4

1, 6: R1 = R2 = H; 2, 7: R1 = H, R2 = F; 3, 8: R1 = H, R2 = Cl; 4, 9: R1 = H, R2 = OMe; 5, 10: R1 = R2 = OMe

11, 25: R1 = R2 = H, R3 = CH3; 12, 26: R1 = H, R2 = F, R3 = CH3; 13, 27: R1 = H, R2 = Cl, R3 = CH3

14, 28: R1 = H, R2 = OMe, R3 = CH3; 15, 29: R1 = R2 = OMe, R3 = CH3; 16, 30: R1 = R2 = H, R3 = (CH3)3C

17, 31: R1 = H, R2 = F, R3 = (CH3)3C; 18, 32: R1 = H, R2 = OMe, R3 = (CH3)3C; 19, 33: R1 = H, R2 = Cl, R3 = Ph

20, 34: R1 = R2 = OMe, R3 = Ph, 21, 35: R1 = R2 = H, R3 = 4-Me-Ph; 22, 36: R1 = H, R2 = OMe, R3 = 4-F-Ph

23, 37: R1 = R2 = H, R3 = 3-MeO-Ph; 24, 38: R1 = H, R2 = Cl, R3 = 3-MeO-Ph

OOAcO

OHO OO

R3O

1 - 5 6 - 10 11 - 24 25 - 38

159

Ketones 11-24 under MacLeod cyclization conditions [13] upon heating with NaOH solution (1 N) and subsequent

acidolysis were cyclized smoothly and in high (69-89%) yields to 3-substituted-6-arylfuro[3,2-g]chromen-7-ones (25-38).

Linear annelation of the furan ring at the 6,7-positions of the 3-arylcoumarin was confirmed by PMR spectroscopy.

The PMR spectra of 25-38 showed a simplified splitting pattern for the aromatic protons compared with the starting ketones

due to decoupling of the 6-proton of the 3-arylcoumarin ring. Protons H-4 and H-9 in 3-substituted 6-arylfuro[3,2-g]chromen-

7-ones resonated as singlets at 7.82-8.34 and 7.60-7.71 ppm, respectively. Furthermore, PMR spectra of 6-arylfuro[3,2-

g]chromen-7-ones 25-38 exhibited a singlet for proton H-2, a characteristic feature of annelation of the furocoumarin ring.

The singlet of proton H-2 was located at 7.56-7.97 ppm with alkyl substituents (25-32) in the 3-position of the 6-arylfuro[3,2-

g]chromen-7-one. Aryl substituents in the 3-position (33-38) shifted the resonance of H-2 to weaker (8.37-8.48 ppm) field.

EXPERIMENTAL

The course of reactions and purity of products were monitored by TLC on Merck 60 F254 plates with CHCl3:CH3OH

(9:1 and 19:1) as eluents. Melting points were determined on a Kofler block. PMR spectra were recorded on Varian VXR-300

and Mercury 400 spectrometers at 300 and 400 MHz, respectively, relative to TMS (internal standard). Elemental analyses of

all compounds agreed with those calculated.

7-Acetoxy-3-arylcoumarins 1-5. A mixture of 2,4-dihydroxybenzaldehyde (13.8 g, 0.1 mol), the appropriate arylacetic

acid (0.1 mol), freshly distilled acetic anhydride (30 mL), and anhydrous pyridine (30 mL) was refluxed for 12 h and cooled.

The resulting precipitate was filtered off and crystallized from propanol-2.

7-Acetoxy-3-phenylchromen-2-one (1): yield 56%, mp 187-188°C (lit. [14] 182-183°C, [15] 182-184°C, [16] 184-

185°C, [17] 185-187°C, [18] 186°C), C17H12O4.

PMR spectrum (400 MHz, DMSO-d6, δ, ppm, J/Hz): 2.33 (3H, s, CH3COO-7), 7.18 (1H, dd, J = 2.0, 8.0, H-6), 7.32

(1H, d, J = 2.0, H-8), 7.44 (3H, m, H-3′, H-4′, H-5′), 7.72 (2H, d, J = 8.0, H-2′, H-6′), 7.82 (1H, d, J = 8.0, H-5), 8.26 (1H, s,

H-4).

3-(4-Fluorophenyl)-7-acetoxychromen-2-one (2): yield 67%, mp 203-204°C (lit. [12] 208°C), C17H11FO4.

PMR spectrum (400 MHz, DMSO-d6, δ, ppm, J/Hz): 2.31 (3H, s, CH3COO-7), 7.19 (1H, dd, J = 2.0, 8.0, H-6), 7.28-

7.33 (3H, m, H-8, H-3′, H-5′), 7.77 (2H, m, H-2′, H-6′), 7.80 (1H, d, J = 8.0, H-5), 8.26 (1H, s, H-4).

3-(4-Chlorophenyl)-7-acetoxychromen-2-one (3): yield 71%, mp 206-207°C (lit. [12] 202°C), C17H11ClO4.

PMR spectrum (300 MHz, CDCl3, δ, ppm, J/Hz): 2.36 (3H, s, CH3COO-7), 7.08 (1H, dd, J = 2.1, 8.1, H-6), 7.16 (1H,

d, J = 2.1, H-8), 7.42 (2H, d, J = 8.1, H-3′, H-5′), 7.55 (1H, d, J = 8.1, H-5), 7.64 (2H, d, J = 8.1, H-2′, H-6′), 7.80 (1H, s,

H-4).

7-Acetoxy-3-(4-methoxyphenyl)chromen-2-one (4): yield 64%, mp 181-182°C (lit. [19] 178°C, [20] 177-178°C),

C18H14O5.

PMR spectrum (300 MHz, CDCl3, δ, ppm, J/Hz): 2.35 (3H, s, CH3COO-7), 3.85 (3H, s, CH3O-4′), 6.98 (2H, d,

J = 8.7, H-3′, H-5′), 7.08 (1H, dd, J = 2.1, 8.1, H-6), 7.14 (1H, d, J = 2.1, H-8), 7.52 (1H, d, J = 8.1, H-5), 7.66 (2H, d, J = 8.7,

H-2′, H-6′), 7.74 (1H, s, H-4).

7-Acetoxy-3-(3,4-dimethoxyphenyl)chromen-2-one (5): yield 68%, mp 179-180°C (lit. [17] 173-175°C), C19H16O6.

PMR spectrum (300 MHz, CDCl3, δ, ppm, J/Hz): 2.35 (3H, s, CH3COO-7), 3.93 and 3.95 (6H, 2s, CH3O-3′,

CH3O-4′), 6.94 (1H, d, J = 8.4, H-5′), 7.07 (1H, dd, J = 2.1, 8.1, H-6), 7.15 (1H, d, J = 2.1, H-8), 7.26-7.30 (2H, m, H-2′,

H-6′), 7.54 (1H, d, J = 8.1, H-5), 7.77 (1H, s, H-4).

7-Hydroxy-3-arylcoumarins 6-10. A suspension of acetate 1-5 (50 mmol) in ethanol (50 mL) was treated with

H2SO4 (20 mL, 20%), refluxed for 5-10 h (end of reaction determined by TLC), and cooled. The resulting solid was filtered

off.

7-Hydroxy-3-phenylchromen-2-one (6): yield 86%, mp 205-206°C (lit. [21] 204-205°C, [15] 206-208°C, [22]

207-208°C, [23] 209°C, [14, 18, 24] 209-210°C, [25] 211-212°C, [26] 212-213°C), C15H10O3.

PMR spectrum (400 MHz, DMSO-d6, δ, ppm, J/Hz): 6.76 (1H, d, J = 2.0, H-8), 6.80 (1H, dd, J = 2.0, 8.0, H-6),

7.38-7.46 (3H, m, H-3′, H-4′, H-5′), 7.61 (1H, d, J = 8.0, H-5), 7.69 (2H, d, J = 8.0, H-2′, H-6′), 8.16 (1H, s, H-4), 10.63 (1H,

br.s, OH-7).

3-(4-Fluorophenyl)-7-hydroxychromen-2-one (7): yield 89%, mp 238-239°C (lit. [12] 245°C), C15H9FO3.

160

PMR spectrum (400 MHz, DMSO-d6, δ, ppm, J/Hz): 6.76 (1H, d, J = 2.0, H-8), 6.83 (1H, dd, J = 2.0, 8.0, H-6), 7.23

(2H, t, J = 8.8, H-3′, H-5′), 7.60 (1H, d, J = 8.0, H-5), 7.75 (2H, m, H-2′, H-6′), 8.16 (1H, s, H-4), 10.47 (1H, br.s, OH-7).

3-(4-Chlorophenyl)-7-hydroxychromen-2-one (8): yield 91%, mp 271-272°C (lit. [27] 280-282°C, [23] 289°C,

[12] 295°C), C15H9ClO3.

PMR spectrum (400 MHz, DMSO-d6, δ, ppm, J/Hz): 6.76 (1H, d, J = 2.0, H-8), 6.84 (1H, dd, J = 2.0, 8.0, H-6), 7.50

(2H, d, J = 8.4, H-3′, H-5′), 7.60 (1H, d, J = 8.0, H-5), 7.74 (2H, d, J = 8.4, H-2′, H-6′), 8.20 (1H, s, H-4), 10.65 (1H, br.s,

OH-7).

7-Hydroxy-3-(4-methoxyphenyl)chromen-2-one (9): yield 82%, mp 215-216°C (lit. [28] 210-212°C, [19] 232°C,

[12] 240°C), C16H12O4.

PMR spectrum (400 MHz, DMSO-d6, δ, ppm, J/Hz): 3.80 (3H, s, CH3O-4′), 6.75 (1H, d, J = 2.0, H-8), 6.82 (1H, dd,

J = 2.0, 8.0, H-6), 7.00 (2H, d, J = 8.4, H-3′, H-5′), 7.58 (1H, d, J = 8.0, H-5), 7.66 (2H, d, J = 8.4, H-2′, H-6′), 8.08 (1H, s,

H-4), 10.55 (1H, br.s, OH-7).

7-Hydroxy-3-(3,4-dimethoxyphenyl)chromen-2-one (10): yield 87%, mp 219-220°C (lit. [17] 221-223°C),

C17H14O5.

PMR spectrum (400 MHz, DMSO-d6, δ, ppm, J/Hz): 3.80 and 3.18 (6H, 2s, CH3O-3′, CH3O-4′), 6.75 (1H, d, J = 2.0,

H-8), 6.83 (1H, dd, J = 2.0, 8.0, H-6), 7.00 (1H, d, J = 8.4, H-5′), 7.30 (2H, m, H-2′, H-6′), 7.57 (1H, d, J = 8.0, H-5), 8.11 (1H,

s, H-4), 10.56 (1H, br.s, OH-7).

Ketones 11-24. A hot solution of coumarins 5-10 (4 mmol) in anhydrous acetone (30 mL) was treated with freshly

calcined potash (1.38 g, 10 mmol), stirred vigorously and heated (50-56°C), treated with the appropriate

-haloketone

(4.2 mmol), held for 1-5 h with heating, stirred vigorously (course of reaction monitored by TLC), and poured into H2SO4

solution (100 mL, 1 N). The resulting precipitate was filtered off and crystallized from propanol-2.

7-(2-Oxopropoxy)-3-phenylchromen-2-one (11): yield 78%, mp 179-180°C, C18H14O4.

PMR spectrum (400 MHz, DMSO-d6, δ, ppm, J/Hz): 2.18 (3H, s, CH3-3′′), 5.00 (2H, s, CH2-1′′), 6.98 (1H, dd,

J = 2.0, 8.0, H-6), 7.00 (1H, d, J = 2.0, H-8), 7.37-7.46 (3H, m, H-3′, H-4′, H-5′), 7.67-7.71 (3H, m, H-5, H-2′, H-6′), 8.20 (1H,

s, H-4).

3-(4-Fluorophenyl)-7-(2-oxopropoxy)chromen-2-one (12): yield 85%, mp 193-194°C, C18H13FO4.

PMR spectrum (400 MHz, DMSO-d6, δ, ppm, J/Hz): 2.18 (3H, s, CH3-3′′), 5.00 (2H, s, CH2-1′′), 6.98 (1H, dd,

J = 2.0, 8.0, H-6), 7.01 (1H, d, J = 2.0, H-8), 7.28 (2H, t, J = 8.8, H-3′, H-5′), 7.68 (1H, d, J = 8.0, H-5), 7.78 (2H, m, H-2′,

H-6′), 8.20 (1H, s, H-4).

3-(4-Chlorophenyl)-7-(2-oxopropoxy)chromen-2-one (13): yield 88%, mp 216-217°C, C18H13ClO4.

PMR spectrum (400 MHz, DMSO-d6, δ, ppm, J/Hz): 2.18 (3H, s, CH3-3′′), 5.01 (2H, s, CH2-1′′), 6.97 (1H, dd,

J = 2.0, 8.0, H-6), 7.01 (1H, d, J = 2.0, H-8), 7.52 (2H, d, J = 8.8, H-3′, H-5′), 7.70 (1H, d, J = 8.0, H-5), 7.74 (2H, d, J = 8.8,

H-2′, H-6′), 8.25 (1H, s, H-4).

3-(4-Methoxyphenyl)-7-(2-oxopropoxy)chromen-2-one (14): yield 81%, mp 191-192°C, C19H16O5.

PMR spectrum (400 MHz, DMSO-d6, δ, ppm, J/Hz): 2.18 (3H, s, CH3-3′′), 4.98 (2H, s, CH2-1′′), 3.18 (3H, s,

CH3O-4′), 6.95 (2H, d, J = 8.4, H-3′, H-5′), 6.98 (1H, dd, J = 2.0, 8.0, H-6), 7.00 (1H, d, J = 2.0, H-8), 7.64 (2H, d, J = 8.4,

H-2′, H-6′), 7.69 (1H, d, J = 8.0, H-5), 8.21 (1H, s, H-4).

3-(3,4-Dimethoxyphenyl)-7-(2-oxopropoxy)chromen-2-one (15): yield 89%, mp 196-197°C, C20H18O6.

PMR spectrum (400 MHz, DMSO-d6, δ, ppm, J/Hz): 2.18 (3H, s, CH3-3′′), 4.98 (2H, s, CH2-1′′), 3.81 and 3.82 (6H,

2s, CH3O-3′, CH3O-4′), 6.95 (1H, d, J = 8.4, H-5′), 6.97 (1H, dd, J = 2.0, 8.0, H-6), 7.00 (1H, d, J = 2.0, H-8), 7.28 (2H, m,

H-2′, H-6′), 7.70 (1H, d, J = 8.0, H-5), 8.24 (1H, s, H-4).

7-(3,3-Dimethyl-2-oxobutoxy)-3-phenylchromen-2-one (16): yield 76%, mp 185-186°C, C21H20O4.

PMR spectrum (400 MHz, DMSO-d6, δ, ppm, J/Hz): 1.20 [9H, s, (CH3)3], 5.18 (2H, s, CH2-1′′), 6.97 (1H, dd,

J = 2.0, 8.0, H-6), 7.01 (1H, d, J = 2.0, H-8), 7.37-7.46 (3H, m, H-3′, H-4′, H-5′), 7.66-7.70 (3H, m, H-5, H-2′, H-6′), 8.19 (1H,

s, H-4).

7-(3,3-Dimethyl-2-oxobutoxy)-3-(4-fluorophenyl)chromen-2-one (17): yield 87%, mp 198-199°C, C21H19FO4.

PMR spectrum (400 MHz, DMSO-d6, δ, ppm, J/Hz): 1.19 [9H, s, (CH3)3], 5.19 (2H, s, CH2-1′′), 6.98 (1H, dd,

J = 2.0, 8.0, H-6), 7.01 (1H, d, J = 2.0, H-8), 7.29 (2H, t, J = 8.8, H-3′, H-5′), 7.68 (1H, d, J = 8.0, H-5), 7.78 (2H, m, H-2′,

H-6′), 8.19 (1H, s, H-4).

161

7-(3,3-Dimethyl-2-oxobutoxy)-3-(4-methoxyphenyl)chromen-2-one (18): yield 79%, mp 187-188°C, C21H19O4.

PMR spectrum (400 MHz, DMSO-d6, δ, ppm, J/Hz): 1.20 [9H, s, (CH3)3], 5.21 (2H, s, CH2-1′′), 3.81 (3H, s,

CH3O-4′), 6.95 (2H, d, J = 8.4, H-3′, H-5′), 6.97 (1H, dd, J = 2.0, 8.0, H-6), 7.00 (1H, d, J = 2.0, H-8), 7.65 (2H, d, J = 8.4,

H-2′, H-6′), 7.69 (1H, d, J = 8.0, H-5), 8.21 (1H, s, H-4).

3-(4-Chlorophenyl)-7-(2-oxo-2-phenylethoxy)chromen-2-one (19): yield 78%, mp 239-240°C, C23H15ClO4.

PMR spectrum (300 MHz, DMSO-d6, δ, ppm, J/Hz): 5.70 (2H, s, CH2-1′′), 7.01 (1H, dd, J = 2.1, 8.1, H-6), 7.10 (1H,

d, J = 2.1, H-8), 7.45 (2H, d, J = 8.7, H-3′, H-5′), 7.56 (3H, t, J = 7.5, H-3′″, H-4′″, H-5′″), 7.67 (1H, d, J = 8.0, H-5), 7.73 (2H,

d, J = 8.8, H-2′, H-6′), 8.04 (2H, d, J = 8.7, H-2′″, H-5′″), 8.21 (1H, s, H-4).

3-(3,4-Dimethoxyphenyl)-7-(2-oxo-2-phenylethoxy)chromen-2-one (20): yield 87%, mp 226-227°C, C25H20O6.

PMR spectrum (300 MHz, DMSO-d6, δ, ppm, J/Hz): 3.82 and 3.83 (6H, 2s, CH3O-3′, CH3O-4′), 5.68 (2H, s,

CH2-1′′), 6.96 (1H, d, J = 8.4, H-5′), 6.99 (1H, dd, J = 2.1, 8.1, H-6), 7.08 (1H, d, J = 2.1, H-8), 7.28 (2H, m, H-2′, H-6′), 7.56

(2H, t, J = 7.5, H-3′″, H-5′″), 7.63 (1H, d, J = 8.1, H-5), 7.68 (1H, m, H-4′″), 8.04 (2H, d, J = 7.2, H-2′″, H-6′″), 8.10 (1H, s,

H-4).

7-[2-(4-Methylphenyl)-2-oxoethoxy]-3-phenylchromen-2-one (21): yield 83%, mp 228-229°C, C24H18O4.

PMR spectrum (400 MHz, DMSO-d6, δ, ppm, J/Hz): 2.40 (3H, s, Me-4′″), 5.72 (1H, s, CH2-1′′), 6.98 (1H, dd,

J = 2.0, 8.0, H-6), 7.00 (1H, d, J = 2.0, H-8), 7.37-7.46 (5H, m, H-3′, H-4′, H-5′, H-3′″, H-5′″), 7.67-7.71 (3H, m, H-5, H-2′,

H-6′), 7.94 (2H, d, J = 7.6, H-2′″, H-6′″), 8.20 (1H, s, H-4).

7-[2-(4-Fluorophenyl)-2-oxoethoxy]-3-(4-methoxyphenyl)chromen-2-one (22): yield 91%, mp 233-234°C,

C24H17FO5.

PMR spectrum (300 MHz, DMSO-d6, δ, ppm, J/Hz): 3.81 (3H, s, CH3O-4′), 5.63 (2H, s, CH2-1′′), 6.95 (2H, d,

J = 8.7, H-3′, H-5′), 6.97 (1H, dd, J = 2.1, 8.1, H-6), 7.06 (1H, d, J = 2.1, H-8), 7.33 (2H, t, J = 8.7, H-3′″, H-5′″), 7.62 (1H, d,

J = 8.1, H-5), 7.64 (2H, d, J = 8.7, H-2′, H-6′), 8.03 (1H, s, H-4), 8.13 (2H, m, H-2′″, H-6′″).

7-[2-(3-Methoxyphenyl)-2-oxoethoxy]-3-phenylchromen-2-one (23): yield 85%, mp 241-242°C, C24H18O4.

PMR spectrum (300 MHz, DMSO-d6, δ, ppm, J/Hz): 3.85 (3H, s, OCH3-3′″), 5.62 (2H, s, CH2-1′′), 6.98 (1H, dd,

J = 2.1, 8.1, H-6), 7.00 (1H, d, J = 2.1, H-8), 7.22 (1H, dd, J = 2.7, 8.4, H-4′″), 7.37-7.41 (3H, m, H-3′, H-4′, H-5′), 7.45 (1H,

t, J = 8.4, H-5′″), 7.51 (1H, dd, J = 2.7, 2.7, H-2′″), 7.62 (1H, d, J = 8.4, H-6′″), 7.67-7.71 (3H, m, H-5, H-2′, H-6′), 8.20 (1H,

s, H-4).

3-(4-Chlorophenyl)-7-[2-(3-methoxyphenyl)-2-oxoethoxy]chromen-2-one (24): yield 92%, mp 248-249°C,

C24H17ClO5.

PMR spectrum (300 MHz, DMSO-d6, δ, ppm, J/Hz): 3.85 (3H, s, OCH3-3′″), 5.62 (2H, s, CH2-1′′), 6.97 (1H, dd,

J = 2.1, 8.1, H-6), 7.01 (1H, d, J = 2.1, H-8), 7.22 (1H, dd, J = 2.7, 8.4, H-4′″), 7.45 (1H, t, J = 8.4, H-5′″), 7.50 (1H, dd, J = 2.7,

2.7, H-2′″), 7.52 (2H, d, J = 8.7, H-3′, H-5′), 7.62 (1H, d, J = 8.4, H-6′″), 7.70 (1H, d, J = 8.1, H-5), 7.74 (2H, d, J = 8.7, H-2′,

H-6′), 8.21 (1H, s, H-4).

3-Substitited 6-Arylfuro[3,2-g]chromen-7-ones 25-38. A solution or suspension of ketones 11-24 (2 mmol) in

propanol-2 (10 mL) was treated with NaOH solution (10 mL, 1 N), heated for 3-4 h (course of reaction monitored by TLC),

and poured into H2SO4 solution (100 mL, 1 N). The resulting precipitate was filtered off and crystallized from propanol-2.

3-Methyl-6-phenylfuro[3,2-g]chromen-7-one (25): yield 69%, mp 219-220°C, C18H12O3.

PMR spectrum (400 MHz, DMSO-d6, δ, ppm, J/Hz): 2.25 (3H, s, CH3-3), 7.47 (3H, m, H-3′, H-4′, H-5′), 7.71 (1H,

s, H-9), 7.73 (2H, d, J = 7.6, H-2′, H-6′), 7.90 (1H, s, H-2), 8.01 (1H, s, H-4), 8.37 (1H, s, H-5).

6-(4-Fluorophenyl)-3-methylfuro[3,2-g]chromen-7-one (26): yield 83%, mp 224-225°C, C18H11FO3.

PMR spectrum (400 MHz, DMSO-d6, δ, ppm, J/Hz): 2.25 (3H, s, CH3-3), 7.31 (2H, t, J = 8.0, H-3′, H-5′), 7.60 (1H,

s, H-9), 7.78 (2H, m, H-2′, H-6′), 7.94 (1H, s, H-2), 7.82 (1H, s, H-4), 8.37 (1H, s, H-5).

6-(4-Chlorophenyl)-3-methylfuro[3,2-g]chromen-7-one (27): yield 89%, mp 233-234°C, C18H11ClO3.

PMR spectrum (400 MHz, DMSO-d6, δ, ppm, J/Hz): 2.25 (3H, s, CH3-3), 7.51 (2H, d, J = 8.0, H-3′, H-5′), 7.65 (1H,

s, H-9), 7.76 (2H, d, J = 8.0, H-2′, H-6′), 7.97 (1H, s, H-2), 7.86 (1H, s, H-4), 8.36 (1H, s, H-5).

6-(4-Methoxyphenyl)-3-methylfuro[3,2-g]chromen-7-one (28): yield 78%, mp 229-230°C, C19H14O4.

PMR spectrum (400 MHz, DMSO-d6, δ, ppm, J/Hz): 2.25 (3H, s, CH3-3), 3.82 (3H, s, CH3O-4′), 7.04 (2H, d, J = 8.8,

H-3′, H-5′), 7.69 (1H, s, H-9), 7.70 (2H, d, J = 8.8, H-2′, H-6′), 7.90 (1H, s, H-2), 7.99 (1H, s, H-4), 8.30 (1H, s, H-5).

6-(3,4-Dimethoxyphenyl)-3-methylfuro[3,2-g]chromen-7-one (29): yield 81%, mp 221-222°C, C20H16O5.

162

PMR spectrum (400 MHz, DMSO-d6, δ, ppm, J/Hz): 2.25 (3H, s, CH3-3), 3.82 and 3.83 (6H, 2s, CH3O-3′,

CH3O-4′), 7.04 (1H, d, J = 8.8, H-5′), 7.34 (2H, m, H-2′, H-6′), 7.68 (1H, s, H-9), 7.88 (1H, s, H-2), 7.96 (1H, s, H-4), 8.33

(1H, s, H-5).

3-t-Butyl-6-phenylfuro[3,2-g]chromen-7-one (30): yield 75%, mp 196-197°C, C21H18O3.

PMR spectrum (300 MHz, DMSO-d6, δ, ppm, J/Hz): 1.44 [9H, s, (CH3)3], 7.43 (3H, m, H-3′, H-4′, H-5′), 7.58 (1H,

s, H-2), 7.70 (1H, s, H-9), 7.73 (2H, d, J = 7.8, H-2′, H-6′), 8.23 (1H, s, H-4), 8.37 (1H, s, H-5).

3-t-Butyl-6-(4-fluorophenyl)furo[3,2-g]chromen-7-one (31): yield 83%, mp 205-206°C, C21H17FO3.

PMR spectrum (300 MHz, DMSO-d6, δ, ppm, J/Hz): 1.44 [9H, s, (CH3)3], 7.24 (2H, t, J = 8.1, H-3′, H-5′), 7.58 (1H,

s, H-2), 7.70 (1H, s, H-9), 7.78 (2H, m, H-2′, H-6′), 8.22 (1H, s, H-4), 8.38 (1H, s, H-5).

3-t-Butyl-6-(4-methoxyphenyl)furo[3,2-g]chromen-7-one (32): yield 87%, mp 219-220°C, C22H20O4.

PMR spectrum (300 MHz, DMSO-d6, δ, ppm, J/Hz): 1.44 [9H, s, (CH3)3], 3.82 (3H, s, CH3O-4′), 7.00 (2H, d,

J = 8.7, H-3′, H-5′), 7.56 (1H, s, H-2), 7.68 (2H, d, J = 8.7, H-2′, H-6′), 7.69 (1H, s, H-9), 8.19 (1H, s, H-4), 8.30 (1H, s, H-5).

6-(4-Chlorophenyl)-3-phenylfuro[3,2-g]chromen-7-one (33): yield 81%, mp 246-247°C, C23H13ClO3.

PMR spectrum (300 MHz, DMSO-d6, δ, ppm, J/Hz): 7.40-7.54 (5H, m, H-3′, H-5′, H-3′′, H-4′′, H-5′′), 7.69 (1H, s,

H-9), 7.76 (4H, d, J = 8.1, H-2′, H-6′, H-2′′, H-6′′), 8.32 (1H, s, H-4), 8.38 (1H, s, H-5), 8.43 (1H, s, H-2).

6-(3,4-Dimethoxyphenyl)-3-phenylfuro[3,2-g]chromen-7-one (34): yield 86%, mp 232-233°C, C25H18O5.

PMR spectrum (300 MHz, DMSO-d6, δ, ppm, J/Hz): 3.82 and 3.83 (6H, 2s, CH3O-3′, CH3O-4′), 7.00 (1H, d, J = 8.7,

H-5′), 7.33 (2H, m, H-2′, H-6′), 7.41 (1H, m, H-4′′), 7.52 (2H, t, J = 7.5, H-3′′, H-5′′), 7.70 (1H, s, H-9), 7.77 (2H, d, J = 7.5,

H-2′′, H-6′′), 8.31 (1H, s, H-4), 8.34 (1H, s, H-5), 8.38 (1H, s, H-2).

3-(4-Methylphenyl)-6-phenylfuro[3,2-g]chromen-7-one (35): yield 78%, mp 239-240°C, C24H16O3.

PMR spectrum (300 MHz, DMSO-d6, δ, ppm, J/Hz): 2.40 (3H, s, CH3-4′′), 7.32 (2H, d, J = 8.1, H-3′′, H-5′′), 7.43

(3H, m, H-3′, H-4′, H-5′), 7.64 (2H, d, J = 8.1, H-2′, H-6′), 7.69 (1H, s, H-9), 7.73 (2H, d, J = 8.1, H-2′′, H-6′′), 8.31 (1H, s,

H-4), 8.33 (1H, s, H-5), 8.39 (1H, s, H-2).

3-(4-Fluorophenyl)-6-(4-methoxyphenyl)furo[3,2-g]chromen-7-one (36): yield 75%, mp 246-247°C, C24H15FO4.

PMR spectrum (300 MHz, DMSO-d6, δ, ppm, J/Hz): 3.82 (3H, s, CH3O-4′), 7.00 (2H, d, J = 8.7, H-3′, H-5′), 7.31

(2H, t, J = 8.7, H-3′′, H-5′′), 7.68 (2H, d, J = 8.7, H-2′, H-6′), 7.71 (1H, s, H-9), 7.78 (2H, m, H-2′′, H-6′′), 8.29 (1H, s, H-4),

8.30 (1H, s, H-5), 8.37 (1H, s, H-2).

3-(3-Methoxyphenyl)-6-phenylfuro[3,2-g]chromen-7-one (37): yield 83%, mp 247-248°C, C24H16O4.

PMR spectrum (300 MHz, DMSO-d6, δ, ppm, J/Hz): 3.87 (3H, s, CH3O-3′′), 6.96 (1H, dd, J = 2.1, 8.7, H-4′′),

7.27-7.32 (2H, m, H-2′′, H-6′′), 7.42 (1H, t, J = 8.7, H-5′′), 7.47 (3H, m, H-3′, H-4′, H-5′), 7.71 (1H, s, H-9), 7.73 (2H, d,

J = 8.7, H-2′, H-6′), 8.34 (1H, s, H-4), 8.40 (1H, s, H-5), 8.43 (1H, s, H-2).

6-(4-Chlorophenyl)-3-(3-methoxyphenyl)furo[3,2-g]chromen-7-one (38): yield 79%, mp 254-255°C, C24H15ClO4.

PMR spectrum (300 MHz, DMSO-d6, δ, ppm, J/Hz): 3.87 (3H, s, CH3O-3′′), 6.96 (1H, dd, J = 2.1, 8.7, H-4′′),

7.27-7.32 (2H, m, H-2′′, H-6′′), 7.42 (1H, t, J = 8.7, H-5′′), 7.48 (2H, d, J = 8.7, H-3′, H-5′), 7.71 (1H, s, H-9), 7.77 (2H, d,

J = 8.7, H-2′, H-6′), 8.34 (1H, s, H-4), 8.41 (1H, s, H-5), 8.48 (1H, s, H-2).

ACKNOWLEDGMENT

We thank OAO Eximed (Kiev, Ukraine) for help in performing the work.

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