Process for the preparation of pyrylium salts

Abstract

The present invention relates to the process for the preparation of Pyrylium salts having the formula represented below. Present invention provide a simplified method of producing symmetrical and unsymmetrical pyrylium salts. The invention explores readily available starting materials with reaction conditions which are suitable for industrial scale applications. All the synthesized compounds were confirmed by various spectroscopic techniques such as Fourier transform infrared spectroscopy, 1H NMR, 13C NMR, 19F NMR spectroscopy, and single-crystal X-ray analysis. Mass of the compounds confirmed by HRMS analysis. ##STR00001##

Claims

1. A process for the preparation of salt having the general formula I, ##STR00004## wherein, in formula I: X is oxygen; R is selected from the group consisting of: a phenyl radical having substitution selected from CH.sub.3, OCH.sub.3, OH, Br, Cl, F, or CF.sub.3; a heteroaryl radical selected from substituted thiophene-or substituted furan; a naphthyl radical; and a fused cyclohexyl and octahydro naphthalenyl radical; R.sub.1 is selected from the group consisting of: a phenyl radical having a substitution selected from CH.sub.3, OCH.sub.3, OH, Br, Cl, F, or CF.sub.3; and a heteroaryl radical selected from substituted thiophene or substituted furan; and R.sub.2 is selected from the group consisting of: a phenyl radical having a substitution selected from CH.sub.3, OCH.sub.3, OH, Br, Cl, F, or CF.sub.3; a heteroaryl radical selected from substituted thiophene or substituted furan; and a phenyl radical substituted with alkyl chain of three carbon atoms; and Z is an anionic function selected from either BF.sub.4− or HOTf.sup.−; said process comprising the steps of: a) condensing ##STR00005## with ##STR00006## in the presence of NaOH to yield ##STR00007## b) cyclizing the ##STR00008## obtained in step (a) by either treating with ##STR00009## and BF.sub.3.OEt.sub.2, or treating with ##STR00010## and HOTf− in cyclohexane at 60° C.-70° C., and stirring for three to six hours under an oxygen atmosphere to obtain a reaction mixture; c) pouring the reaction mixture obtained in step (b) into diethyl ether to precipitate a product; d) washing the product with diethyl ether and drying the product in air; and e) crystallizing from ethanol to obtain a salt having the general formula I.

2. The process as claimed in claim 1, wherein R or R.sub.1 is a phenyl radical having a substitution selected from a group consisting of Cl, Br, and F.

3. The process as claimed in claim 1, wherein R or R.sub.1 is a phenyl radical having a substitution selected from a group consisting of CH.sub.3, OCH.sub.3, OH, and CF.sub.3.

4. The process as claimed in claim 1, wherein R is naphthyl radical.

5. The process as claimed in claim 1, wherein R or R.sub.1 consists of substituted furan or substituted thiophene.

6. The process as claimed in claim 1, wherein ##STR00011## is phenyl acetylene and is substituted at para position with an alkyl chain of three carbon atoms.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 represents the general structure of the pyrylium ion

(2) FIG. 2 represents the schematic diagram depicting the process protocol to prepare pyrylium ions

(3) FIG. 3 represents the schematic diagram depicting the process protocol to prepare fused-pyrylium ions

(4) FIG. 4 represents the library of compounds synthesized through the invented protocol.

(5) FIG. 5 represents Single-Crystal X-Ray structure for compound B6 (CCDC 1574744)

DETAILED DESCRIPTION OF THE INVENTION

(6) The present invention relates to the process for the preparation of Pyrylium salts. Present invention provide a simplified method of producing symmetrical and unsymmetrical pyrylium salts. The present process provide a notable versatility in the substituents incorporated into these pyrylium salts and at the same time provide a direct and efficient synthesis of these salts. Present invention provide a novel process of pyrylium salts preparation by condensing an acetophenone with aldehyde in the presence of NaOH, treating the resultant product with phenyl acetylenes or heterocyclic appended acetylenes in the presence of BF.sub.3.OEt.sub.2 to form the cyclised product of pyrylium salts. Other strong bases like KOtBu, KOH may be used to generate the enolate of the methyl ketone for the reaction with aldehyde to form α,β-unsaturated ketones in a variety of solvents such as Ethanol, Methanol, DCM. In one of the embodiment of the invention, the process used is a four component, two-step involving the synthesis of α,β-unsaturated ketones (Examples shown in the examples section) followed by the cyclisation of these α,β-unsaturated ketones with various substituted alkynes in the presence of BF.sub.3.OEt.sub.2 will provide a pyrylium salts of the formula (FIG. 1).

(7) In another embodiment of the invention, alternatively, after the preparation of α,β-unsaturated ketones, to the same reaction vessel BF.sub.3.OEt.sub.2 and various substituted alkynes will be added to facilitate the cyclisation in one pot three component fashion. As generally shown in reaction (FIG. 2).

(8) In still another embodiment of the invention, acetophenones on condensation with aldehydes in presence of NaOH in ethanol will yield the α,β-unsaturated ketones (A). The intermediate product A was added to an aryl or heteroaryl acetylenes and BF.sub.3.OEt.sub.2 in dry cyclohexane at 60-70° C., and stirred for 3-6 hrs under the oxygen atmosphere. After the completion of reaction, the reaction mixture was poured in to diethyl ether to precipitate the product. The product is filtered off, washed with diethyl ether, dried in air and crystallised from ethanol to get the crystalline pyrylium salts (B).

(9) In yet Another embodiment of the invention, novel process also illustrated for the preparation of fused pyrylium salts. Arylidene ketones (C) was added to an aryl or heteroaryl acetylenes and BF.sub.3.OEt.sub.2 in dry cylcohexane at 60° C., and stirred for 3-6 hrs under the oxygen atmosphere. After the completion of reaction, the reaction mixture was poured in to diethyl ether to precipitate the product (D) and crystallised from ethanol to get the crystalline compounds (FIG. 3).

(10) In another embodiment of the invention, an added novelty of reaction is the use of three equivalents of BF.sub.3.OEt.sub.2 in the formation of pyrylium salts which results in the column free isolation of the products by suppressing the side reactions. In this novel process of the pyrylium salts, two methods utilised. In the first method, α,β-unsaturated ketones are isolated prior to cyclisation and in the second method, without further purification or separation of α,β-unsaturated ketones, react with substituted alkynes insitu, which will be subjected to facilitate the cyclisation in the same reaction vessel.

(11) In still another embodiment of the invention, all the reaction steps of said process were monitored by chromatography and the crude products obtained were subjected to purification using crystallization to get the pure compounds in good yields. Further, all the resultant compounds/products were systematically characterized using various analytical and spectral methods.

WORKING EXAMPLES

(12) Following examples are given by way of illustration and therefore should not be construed to limit the scope of the invention.

Example 1

(13) General Preparation of 2,4,6-triphenylpyrylium tetrafluoroborate [B1]

(14) 3 eq. of BF.sub.3.OEt.sub.2 (102.18 mg, 0.09 ml, 0.72 mmol), dissolved in 1 ml of cyclohexane is added to the mixture of phenyl acetylene (74 mg, 0.72 mmol), and Compound A1(E-Chalcone), prepared by the method described by (T. M. Kadayat, C. Park, K. Y. Jun, T. T. Magar, G. Bist, H. Y. Yoo, Y. Kwon and E. S. Lee, Bioorg. Med. Chem., 2015, 23, 3499) (50 mg, 0.24 mmol) in dry cyclohexane (2 ml) under the oxygen atmosphere. The solution was stirred for 3 hrs at 60° C. After completion of the reaction, the reaction mixture was poured in to 10 ml of diethyl ether dissolving the residue in DCM (5 ml), to precipitate the product. The product was filtered and washed with diethyl ether and dried in air. Recrystallization from ethanol afforded the compound 2,4,6-triphenylpyrylium tetrafluoroborate as yellow crystals; 62 mg (65%), m.p=225-227° C.; IR (neat, cm.sup.−1): 3069, 2923, 1621 (—C═O+), 1592, 1468, 1272, 1194, 1049, 986, 763; .sup.1H NMR (500 MHz, DMSO-d6): δ 7:84 8.67 (m, 15 aromatic H), 9.24 (s, 2H); .sup.13C NMR (125 MHz, DMSO-d6): δ 115.1, 128.8, 129.1, 129.8, 129.9, 130.0, 132.4, 135.0, 135.2, 165.1, 170.0; HRMS C.sub.23H.sub.17O.sup.+ ([M].sup.+): 309.1284.

Example 2

Preparation of 2,6-diphenyl-4-(p-tolyl)pyryliumtetrafluoroborate [B2]

(15) 3 eq. of BF.sub.3.OEt.sub.2 (102.18 mg, 0.08 ml, 0.72 mmol), dissolved in 1 ml of cyclohexane is added to the mixture of phenyl acetylene (68.63 mg, 0.67 mmol), and Compound A2 ((E)-1-phenyl-3-(p-tolyl)prop-2-en-1-one), prepared by the method described by (T. M. Kadayat, C. Park, K. Y. Jun, T. T. Magar, G. Bist, H. Y. Yoo, Y. Kwon and E. S. Lee, Bioorg. Med. Chem., 2015, 23, 3499) (50 mg, 0.22 mmol) in dry cyclohexane (2 ml) under oxygen atmosphere. The solution was stirred for 3 hrs at 60° C. After completion of the reaction, the reaction mixture was poured in to 10 ml of diethyl ether dissolving the residue in DCM (95 ml), to precipitate the product. The product was filtered and washed with diethyl ether and dried in air. Recrystallization from ethanol afforded the compound 2,6-diphenyl-4-(p-tolyl) pyrylium tetrafluoroborate as yellow crystals; 65 mg (70%), m.p=257-259° C.; IR (neat, cm.sup.−1): 2920, 2851, 1624 (—C═O+), 1599, 1491, 1254, 1195, 1060, 1027, 822; .sup.1H NMR (500 MHz, DMSO-d.sub.6): δ 2.53 (s, 3H, —CH.sub.3), 6.63-8.59 (m, 14 aromatic H), 79.41 (s, 2H); .sup.13C NMR (125 MHz, DMSO-d.sub.6): δ 21.4, 114.3, 128.7, 129.1, 129.5, 129.8, 130.2, 130.6, 134.9, 147.0, 164.6, 169.7; HRMS for C.sub.24H.sub.19O.sup.+ ([M].sup.+): 323.1437.

Example 3

Preparation of 4-(4-methoxyphenyl)-2,6-diphenylpyrylium tetrafluoroborate [B3]

(16) 3 eq. of BF.sub.3.OEt.sub.2 (89.42 mg, 0.07 ml, 0.63 mmol), dissolved in 1 ml of cyclohexane is added to the mixture of phenyl acetylene (64.34 mg, 0.63 mmol), and Compound A3 ((E)-3-(4-methoxyphenyl)-1-phenylprop-2-en-1-one), prepared by the method described by (T. M. Kadayat, C. Park, K. Y. Jun, T. T. Magar, G. Bist, H. Y. Yoo, Y. Kwon and E. S. Lee, Bioorg. Med. Chem., 2015, 23, 3499) (50 mg, 0.21 mmol) in dry cyclohexane (2 ml) under the oxygen atmosphere. The solution was stirred for 3 hrs at 60° C. After completion of the reaction, the reaction mixture was poured in to 10 ml of diethyl ether dissolving the residue in DCM (5 ml), to precipitate the product. The product was filtered and washed with diethyl ether and dried in air. Recrystallization from ethanol afforded the compound 4-(4-methoxyphenyl)-2,6-diphenylpyrylium tetrafluoroborate as red-orange crystals; 50 mg (56%), m.p=218-220° C.; IR (net, cm.sup.−1): 3063, 2924, 2850, 1629 (—C═O+), 1576, 1442, 1246, 1186, 1055, 836; .sup.1H NMR (500 MHz, DMSO-d.sub.6): δ 4.01 (s, 3H, —OCH.sub.3), 7.34-8.72 (m, 14 aromatic H), 9.06 (s, 2H); .sup.13C NMR (125 MHz, DMSO-d.sub.6): δ 61.5, 120.9, 129.6, 133.7, 134.5, 135.0, 139.9, 168.8, 171.1, 174.1; HRMS for C.sub.24H.sub.19O.sub.2.sup.+ ([M].sup.+): 339.1390.

Example 4

Preparation of 4-(4-hydroxyphenyl)-2,6-diphenylpyrylium tetrafluoroborate [B4]

(17) 3 eq. of BF.sub.3.OEt.sub.2 (93.67 mg, 0.08 ml, 0.66 mmol), dissolved in 1 ml of cyclohexane is added to the mixture of phenyl acetylene (67.04 mg, 0.66 mmol), and Compound A4 ((E)-3-(4-hydroxyphenyl)-1-phenylprop-2-en-1-one), prepared by the method described by (T. M. Kadayat, C. Park, K. Y. Jun, T. T. Magar, G. Bist, H. Y. Yoo, Y. Kwon and E. S. Lee, Bioorg. Med. Chem., 2015, 23, 3499) (50 mg, 0.22 mmol) in dry cyclohexane (2 ml) under the oxygen atmosphere. The solution was stirred for 6 hrs, at 60° C. After completion of the reaction, the reaction mixture was poured in to 10 ml of diethyl ether dissolving the residue in DCM (5 ml), to precipitate the product. The product was filtered and washed with diethyl ether and dried in air. Recrystallization from ethanol afforded the compound 4-(4-hydroxyphenyl)-2,6-diphenylpyrylium tetrafluoroborate as orange crystals; 62 mg (67%), m.p=282-285° C.; IR (neat, cm.sup.−1): 3343, 2972, 1633 (—C═O+), 1596, 1491, 1277, 1188, 1120, 1069, 844; .sup.1H NMR (500 MHz, DMSO-d.sub.6): δ 7.13-8.65 (m, 14 aromatic H), 8.99 (s, 2H), 11.41 (brs, 1H, —OH); .sup.13C NMR (125 MHz, DMSO-d.sub.6): δ 112.5, 117.1, 122.8, 128.3, 129.3, 129.7, 133.6, 134.5, 163.4, 165.7, 168.3; HRMS for C.sub.23H.sub.17O.sub.2.sup.+ ([M].sup.+): 325.1239.

Example 5

Preparation of 4-(4-bromophenyl)-2,6-diphenylpyrylium tetrafluoroborate [B5]

(18) 3 eq. of BF.sub.3.OEt.sub.2 (72.38 mg, 0.06 ml, 0.51 mmol), dissolved in 1 ml of cyclohexane is added to the mixture of phenyl acetylene (53.31 mg, 0.51 mmol), and Compound A5 ((E)-3-(4-bromophenyl)-1-phenylprop-2-en-1-one), prepared by the method described by (T. M. Kadayat, C. Park, K. Y. Jun, T. T. Magar, G. Bist, H. Y. Yoo, Y. Kwon and E. S. Lee, Bioorg. Med. Chem., 2015, 23, 3499) (50 mg, 0.17 mmol) in dry cyclohexane (2 ml) under the oxygen atmosphere. The solution was stirred for 3 hrs at 60° C. After completion of the reaction, the reaction mixture was poured in to 10 mi of diethyl ether dissolving the residue in DCM (5 ml), to precipitate the product. The product was filtered and washed with diethyl ether and dried in air. Recrystallization from ethanol afforded the compound 4-(4-bromophenyl)-2,6-diphenylpyrylium tetrafluoroborate as yellow crystals; 39 mg (48%), m.p=260-262° C.; IR (neat, cm.sup.−1): 3057, 2920, 1617 (—C═O+), 1578, 1490, 1275, 1193, 1065, 777, 683; .sup.1H NMR (500 MHz, DMSO-d.sub.6): δ 7.82-8.61 (m, 14 aromatic H), 9.19 (s, 2H); .sup.13C NMR (125 MHz, DMSO-d.sub.6): δ 115.1, 128.8, 129.1, 129.9, 131.6, 131.8, 132.9, 135.1, 163.9, 170.2; HRMS for C.sub.23H.sub.16BrO.sup.+ ([M].sup.+): 387.0384.

Example 6

Preparation of 4-(4-chlorophenyl)-2,6-diphenylpyrylium tetrafluoroborate [B6]

(19) 3 eq. of BF.sub.3.OEt.sub.2 (87.71 mg, 0.08 ml, 0.62 mmol), dissolved in 1 ml of cyclohexane is added to the mixture of phenyl acetylene (63.12 mg, 0.62 mmol), and Compound A6 ((E)-3-(4-chlorophenyl)-1-phenylprop-27en-1-one), prepared by the method described by (T. M. Kadayat, C. Park, K. Y. Jun, T. T. Magar, G. Bist, H. Y. Yoo, Y. Kwon and E. S. Lee, Bioorg. Med. Chem., 2015, 23, 3499) (50 mg, 0.21 mmol) in dry cyclohexane (2 ml) under the oxygen atmosphere. The solution was stirred for 3 hrs at 60° C. After completion of the reaction, the reaction mixture was poured in to 10 ml of diethyl ether dissolving the residue in DCM (5 ml), to precipitate the product. The product was filtered and washed with diethyl ether and dried in air. Recrystallization from ethanol afforded the compound 4-(4-chlorophenyl)-2,6-diphenylpyrylium tetrafluoroborate as yellow crystals; 45 mg (51%), m.p=253-255° C.; IR (neat, cm.sup.−1): 2921, 1622 (—C═O+), 1587, 1492, 1248, 1093, 1047, 825, 778, 731; .sup.1H NMR (500 MHz, DMSO-d.sub.6): δ 7.82-8.66 (m, 14 aromatic H), 9.19 (s, 2H); .sup.13C NMR (125 MHz, DMSO-d.sub.6): δ 115.2, 128.8, 129.1, 129.8, 129.9, 131.8, 135.2, 163.7, 170.2; HRMS for C.sub.23H.sub.16ClO.sup.+ ([M].sup.+): 343.0883.

Example 7

Preparation of 4-(4-fluorophenyl)-2,6-diphenylpyrylium tetrafluoroborate [67]

(20) 3 eq. of BF.sub.3.OEt.sub.2 (94.09 mg, 0.08 ml, 0.66 mmol), dissolved in 1 ml of cyclohexane is added to the mixture of phenyl acetylene (67.71 mg, 0.66 mmol), and Compound A7 ((E)-3-(4-fluorophenyl)-1-phenylprop-2-en-1-one), prepared by the method described by (T. M. Kadayat, C. Park, K. Y. Jun, T. T. Magar, G. Bist, H. Y. Yoo, Y. Kwon and E. S. Lee, Bioorg. Med. Chem., 2015, 23, 3499) (50 mg, 0.22 mmol) in dry cyclohexane (2 ml) under the oxygen atmosphere. The solution was stirred for 3 hrs at 60° C. After completion of the reaction, the reaction mixture was poured in to 10 ml of diethyl ether, dissolving the residue in DCM (5 ml), to precipitate the product. The product was filtered and washed with diethyl ether and dried in Recrystallization from ethanol afforded the compound 4-(4-fluorophenyl)-2,6-diphenylpyrylium tetrafluoroborate as yellow crystals; 59 mg (64%), m.p=208-210° C.; IR (neat, cm.sup.−1): 3062, 2972, 1624 (—C═O+), 1493, 1269, 1166, 1120, 1036, 830, 777; .sup.1H NMR (500 MHz, DMSO-d.sub.6): δ 7.68-8.75 (m, 14 aromatic H), 9.16 (s, 2H); .sup.13C. NMR (125 MHz, DMSO-d.sub.6): δ 114.9, 117.1, 117.2, 128.8, 129.1, 129.9, 133.2, 133.3, 135.1, 163.8, 169.9; HRMS for C.sub.23H.sub.16FO.sup.+ ([M].sup.+): 327.1189.

Example 8

Preparation of 2,6-diphenyl-4-(4-(trifluoromethyl)phenyl)pyryliumtetrafluoroborate [B8]

(21) 3 eq. of BF.sub.3.OEt.sub.2 (77.07 mg, 0.07 ml, 0.54 mmol), dissolved in 1 ml of cyclohexane is added to the mixture of phenyl acetylene (55.47 mg, 0.54 mmol), and Compound A8 ((E)-1-phenyl-3-(4-(trifluoromethyl)phenyl)prop-2-en-1-one), prepared by the method described by (T. M. Kadayat, C. Park, K. Y. Jun, T. T. Magar, G. Bist, H. Y. Yoo, Y. Kwon and E. S. Lee, Bioorg. Med. Chem., 2015, 23, 3499) (50 mg, 0.18 mmol) in dry cyclohexane (2 ml) under the oxygen atmosphere. The solution was stirred for 3 hrs at 60° C. After completion of the reaction, the reaction mixture was poured in to 10 ml of diethyl ether, dissolving the residue in DCM (5 ml), to precipitate the product. The product was filtered and washed with diethyl ether and dried in air.

(22) Recrystallization from ethanol afforded the compound 2,6-diphenyl-4-(4-(trifluoromethyl)phenyl)pyryliumtetrafluoroborate as yellow crystals; 39 mg (47%), m.p=245-247° C.; IR (neat, cm.sup.−1): 3109, 3077, 1622 (—C═O+), 1495, 1322, 1270, 1171, 1065, 1034, 836; .sup.1H NMR (500 MHz, DMSO-d.sub.6): δ 7.59-8.52 (m, 14 aromatic H), 9.03 (s, 2H); .sup.13C NMR (125 MHz, DMSO-d.sub.6): δ 116.3, 126.5, 128.9, 129.9, 130.7, 135.3, 136.5, 163.7, 170.7; HRMS Calcd. for C.sub.24H.sub.16F.sub.3O.sup.+ ([M].sup.+): 377.1159.

Example 9

Preparation of 4-(naphthalen-2-yl)-2,6-diphenylpyrylium tetrafluroborate [B9]

(23) 3 eq. of BF.sub.3.OEt.sub.2 (82.17 mg, 0.07 ml, 0.58 mmol), dissolved in 1 ml of cyclohexane is added to the mixture of phenyl acetylene (59.15 mg, 0.57 mmol), and Compound A9 ((E)-3-(naphthalen-211)-1-phenylprop-2-en-1-one), prepared by the method described by (T. M. Kadayato C. Park, K. Y. Jun, T. T. Magar, G. Bist, H. Y. Yoo, Y. Kwon and E. S. Lee, Bioorg. Med. Chem., 2015, 23, 3499) (50 mg, 0.19 mmol) in dry cyclohexane (2 ml) under the oxygen atmosphere. The solution was stirred for 3 hrs at 60° C. After completion of the reaction, the reaction mixture was poured in to 10 ml of diethyl ether, dissolving the residue in DCM (5 ml), to precipitate the product. The product was filtered and washed with diethyl ether and dried in air. Recrystallization from ethanol afforded the compound 4-(naphthalen-2-yl)-2,6-diphenylpyrylium tetrafluroborate as pale red crystals; 50 mg (58%), m.p=190-193° C.; IR (neat, cm.sup.−1): 3061, 3029, 1611 (—C═O+), 1579, 1492, 1273, 1223, 1158, 777; .sup.1H NMR (500 MHz, DMSO-d.sub.6): δ 7.76-9.35 (m, 19 aromatic H); .sup.13C NMR (125 MHz, DMSO-d.sub.6): δ 115.0, 124.8, 127.8, 127.9, 128.8, 129.2, 129.5, 129.8, 129.9, 130.3, 132.5, 132.6, 135.0, 135.8, 164.7, 169.8; HRMS for C.sub.27H.sub.19O.sup.+ ([M].sup.+): 359.1443.

Example 10

(24) Preparation of 4-(furan-2-yl)-2,6-diphenylpyrylium tetrafluoroborate [610] 3 eq. of BF.sub.3.OEt.sub.2 (107.72 mg, 0.09 ml, 0.75 mmol), dissolved in 1 ml of cyclohexane is added to the mixture of phenyl acetylene (67.04 mg, 0.75 mmol), and Compound A10 ((E)-3-(furan-2-yl)-1-phenylprop-2-en-1-one), prepared by the method described by (T. M. Kadayat, C. Park, K. Y. Jun, T. T. Magar, G. Bist; H. Y. Yoo, Y. Kwon and E. S. Lee, Bioorg. Med. Chem., 2015, 23, 3499) (50 mg, 0.25 mmol) in dry cyclohexane (2 ml) under oxygen atmosphere. The solution was stirred for 3 hrs at 60° C. After completion of the reaction, the reaction mixture was poured in to 10 ml of diethyl ether, dissolving the residue in DCM (5 ml), to precipitate the product. The product was filtered and washed with diethyl ether and dried in air. Recrystallization from ethanol afforded the compound 4-(furan-2-yl)-2,6-diphenylpyrylium tetrafluoroborate as greenish black crystals; 69 mg (71%), m.p=202-204° C.; IR (neat, cm.sup.−1): 3120, 3061, 1626 (—C═O+), 1581, 1495, 1377, 1266, 1063, 946, 766; .sup.1H NMR (500 MHz, CD.sub.3CN): δ 7.06 8.38 (m, 13 aromatic H), 8.49 (s, 2H); .sup.13C NMR (125 MHz, CD.sub.3CN): δ 111.6, 117.5, 126.6, 129.3, 130.1, 130.9, 136.1, 149.6, 154.7, 170.9; HRMS for C.sub.21H.sub.15O.sub.2.sup.+ ([M]): 299.1077.

Example 11

Preparation of 2,6-diphenyl-4-(thiophen-3-yl)pyryliumtetrafluroborate [B11]

(25) 3 eq. of BF.sub.3.OEt.sub.2 (99.21 mg, 0.09 ml, 0.0.69 mmol), dissolved in 1 ml of cyclohexane is added to the mixture of phenyl acetylene (71.38 mg, 0.69 mmol), and Compound A11 ((E)-1-phenyl-3-(thiophen-3-yl)prop-2-en-1-one), prepared by the method described by (T. M. Kadayat, C. Park, K. Y. Jun, T. T. Magar, G. Bist, H. Y. Yoo, Y. Kwon and E. S. Lee, Bioorg. Med. Chem., 2015, 23, 3499) (50 mg, 0.23 mmol) in dry cyclohexane (2 ml) under the oxygen atmosphere. The solution was stirred for 3 hrs at 60° C. After completion of the reaction, the reaction mixture was poured in to 10 ml of diethyl ether, dissolving the residue in DCM (5 ml), to precipitate the product. The product was filtered and washed with diethyl ether and dried in air. Recrystallization from ethanol afforded the compound 2,6-diphenyl-4-(thiophen-3-yl)pyryliumtetrafluroborate as black crystals; 63 mg (67%), m.p=205-207° C.; IR (neat, cm.sup.−1): 3104, 3062, 1622 (—C═O+), 1579, 1492, 1270, 1221, 1055, 775, 700; .sup.1H NMR (500 MHz, DMSO-d.sub.6): δ 7.82-9.51 (m, 15 aromatic H); .sup.13C NMR (125 MHz, DMSO-d.sub.6): δ 113.9, 127.6, 128.5, 129.2, 129.9, 134.9, 136.1, 138.2, 158.2, 169.7; HRMS for C.sub.21H.sub.15OS.sup.+ ([M].sup.+): 315.0849.

Example 12

Preparation of 2-phenyl-4,6-di-p-tolylpyrylium tetrafluoroborate [B12]

(26) 3 eq. of BF.sub.3.OEt.sub.2 (90.01 mg, 0.08 ml, 0.72 mmol), dissolved in 1 ml of cyclohexane is added to the mixture of phenyl acetylene (64.36 mg, 0.63 mmol), and Compound A12 ((E)-1,3-di-p-tolylprop-2-en-1-one), prepared by the method described by (T. M. Kadayat, C. Park, K. Y. Jun, T. T. Magar, G. Bist, H. Y. Yoo, Y. Kwon and E. S. Lee, Bioorg. Med. Chem., 2015, 23, 3499) (50 mg, 0.21 mmol) in dry Cyclohexane (2 ml) under the oxygen atmosphere. The solution was stirred for 3 hrs at 60° C. After completion of the reaction, the reaction mixture was poured in to 10 ml of diethyl ether, dissolving the residue in DCM (5 ml), to precipitate the product. The product was filtered and washed with diethyl ether and dried in air. Recrystallization from ethanol afforded the compound 2-phenyl-4,6-di-p-tolylpyrylium tetrafluoroborate as orange crystals; 42 mg (48%), m.p=214-216° C.; IR (neat, cm.sup.−1): 3124, 2923, 2855, 1624 (—C═O+), 1599, 1491, 1228, 1192 1055, 818; .sup.1H NMR (500 MHz, DMSO-d.sub.6): δ 2.49 (s, 6H, —CH.sub.3), 7.56-8.99 (m, 15 aromatic H); .sup.13C NMR (125 MHz, DMSO-d.sub.6): 21.3, 21.4, 113.7, 113.8, 126.3, 128.5, 128.7, 129.1, 129.5, 129.8, 130.0, 130.5, 130.5, 134.7, 146.3, 146.9, 164.2, 169.1, 169.8; HRMS for C.sub.25H.sub.21O.sup.+ ([M].sup.+): 337.1597.

Example 13

Preparation of 2,4-bis(4-methoxyphenyl)-6-phenylpyrylium tetrafluoroborate [B13]

(27) 3 eq. of BF.sub.3.OEt.sub.2 (80.90 mg, 0.07 ml, 0.57 mmol), dissolved in 1 ml of cyclohexane is added to the mixture of phenyl acetylene (58.23 mg, 0.57 mmol), and Compound A13 ((E)-1,3-bis(4-methoxyphenyl)prop-2-en-1-one), prepared by the method described by (T. M. Kadayat, C. Park, K. Y. Jun, T. T. Magar, G. Bist, H. Y. Yoo, Y. Kwon and E. S. Lee, Bioorg. Med. Chem., 2015, 23, 3499) (50 mg, 0.19 mmol) in dry cyclohexane (2 ml) under the oxygen atmosphere. The solution was stirred for 3 hrs at 60° C. After completion of the reaction, the reaction mixture was poured in to 10 ml of diethyl ether, dissolving the residue in DCM (5 ml), to precipitate the product. The product was filtered and washed with diethyl ether and dried in air. Recrystallization from ethanol afforded the compound 2,4-bis(4-methoxyphenyl)-6-phenylpyrylium tetrafluoroborate as pale-red crystals; 43 mg (51%), m.p=245-247° C.; IR (neat, cm.sup.−1): 3161, 3073, 2923, 1629 (—C═O+), 1589, 1467, 1246, 1056, 951, 836; .sup.1H NMR (500 MHz, DMSO-d.sub.6): δ 3.98-3.99 (m, 6H, —CH.sub.3), 7.31-8.93 (m, 15 aromatic H); .sup.13C NMR (125 MHz, DMSO-d.sub.6): δ 56.0, 56.1, 111.9, 115.4, 121.3, 124.3, 128.1, 129.3, 129.7, 131.0, 132.7, 134.3, 162.5, 164.8, 165.5, 167.5, 168.9; HRMS for C.sub.25H.sub.21O.sub.3.sup.+ ([M].sup.+): 369.1496.

Example 14

Preparation of 2,4-bis(4-chlorophenyl)-6-phenylpyrylium tetrafluoroborate [B14]

(28) 3 eq. of BF.sub.3.OEt.sub.2 (77.06 mg, 0.07 ml, 0.54 mmol), dissolved in 1 ml of cyclohexane is added to the mixture of phenyl acetylene (55.16 mg, 0.54 mmol), and Compound A14 ((E)-1,3-bis(4-chlorophenyl)prop-2-en-1-one), prepared by the method described by (T. M. Kadayat, C. Park, K. Y. Jun, T. T. Magar, G. Bist, H. Y. Yoo, Y. Kwon and E. S. Lee, Bioorg. Med. Chem., 2015, 23, 3499) (50 mg, 0.18 mmol) in dry cyclohexane (2 ml) under the oxygen atmosphere. The solution was stirred for 3 hrs at 60° C. After completion of the reaction, the reaction mixture was poured in to 10 ml of diethyl ether, dissolving the residue in DCM (5 ml), to precipitate the product. The product was filtered and washed with diethyl ether and dried in air. Recrystallization from ethanol afforded the compound 2,4-bis(4-chlorophenyl)-6-phenylpyrylium tetrafluoroborate as yellow crystals; 42 mg (50%), m.p=243-245° C.; IR (neat, cm.sup.−1): 3070, 2922, 1621 (—C═O+), 1586, 1490, 1226, 1121, 1051, 829, 723; .sup.1H NMR (500 MHz, DMSO-d.sub.6): δ 7.81 8.64 (m, 13 aromatic H), 9.18 (s, 2H); .sup.13C NMR (125 MHz, DMSO-d.sub.6): δ 115.3, 127.9, 128.8, 128.9, 129.8, 130.0, 130.5, 131.1, 131.8, 135.3, 140.3, 140.6, 163.7, 169.0, 170.3; HRMS for C.sub.23H.sub.15Cl.sub.2O.sup.+ ([M].sup.+): 377.0509.

Example 15

Preparation of 2,4-bis(4-bromophenyl)-6-phenylpyrylium tetrafluoroborate [B15]

(29) 3 eq. of BF.sub.3.OEt.sub.2 (58.33, 0.05 ml, 0.14 mmol), dissolved in 1 ml of cyclohexane is added to the mixture of phenyl acetylene (42.11 mg, 0.14 mmol), and Compound A15 ((E)-1,3-bis(4-bromophenyl)prop-2-en-1-one), prepared by the method described by (T. M. Kadayat, C. Park, K. Y. Jun, T. T. Magar, G. Bist, H. Y. Yoo, Y. Kwon and E. S. Lee, Bioorg. Med. Chem., 2015, 23, 3499) (50 mg, 0.14 mmol) in dry cyclohexane (2 ml) under the oxygen atmosphere. The solution was stirred for 3 hrs at 60° C. After completion of the reaction, the reaction mixture was poured in to 10 ml of diethyl ether, dissolving the residue in DCM (5 ml), to precipitate the product. The product was filtered and washed with diethyl ether and dried in air. Recrystallization from ethanol afforded the compound 2,4-bis(4-bromophenyl)-6-phenylpyrylium tetrafluoroborate as yellow crystals; 27 mg (36%), m.p=255-257° C.; IR (neat, cm.sup.−1): 3063, 2922, 1622 (—C═O+), 1581, 1493, 1266, 1244, 1055, 821, 722; .sup.1H NMR (500 MHz, DMSO-d.sub.6): δ 7.82-8.61 (m, 13 aromatic H), 9.20 (s, 2H); .sup.13C NMR (125 MHz, DMSO-d.sub.6): 115.2, 115.3, 128.3, 128.9, 129.0, 129.5, 129.9, 130.1, 130.5, 131.5, 131.8, 132.9, 133.0, 135.3, 163.9, 169.2, 170.4; HRMS for C.sub.23H.sub.15Br.sub.2O.sup.+ ([M].sup.+): 464.9489.

Example 16

Preparation of 2,4-bis(4-fluorophenyl)-6-phenylpyrylium tetrafluoroborate [B16]

(30) 3 eq. of BF.sub.3.OEt.sub.2 (85.16 mg, 0.07 ml, 0.60 mmol), dissolved in 1 ml of cyclohexane is added to the mixture of phenyl acetylene (62.52 mg, 0.61 mmol), and Compound A16 ((E)-1,3-bis(4-fluorophenyl)prop-2-en-1-one), prepared by the method, described by (T. M. Kadayat, C. Park, K. Y. Jun, T. T. Magar, G. Bist, H. Y. Yoo, Y. Kwon and E. S. Lee, Bioorg. Med. Chem., 2015, 23, 3499) (50 mg, 0.20 mmol) in dry cyclohexane (2 ml) under the oxygen atmosphere. The solution was stirred for 3 hrs at 60° C. After completion of the reaction, the reaction mixture was poured in to 10 ml of diethyl ether, dissolving the residue in DCM (5 ml), to precipitate the product. The product was filtered and washed with diethyl ether and dried in air. Recrystallization from ethanol afforded the compound name as yellow crystals; 51 mg (57%), m.p=190-192° C.; IR (neat, cm.sup.−1): 3068, 2923, 1626 (—C═O+), 1595, 1496, 1271, 1165, 1051, 834, 774; .sup.1H NMR (500 MHz, DMSO-d.sub.6): δ 7.66-9.15 (m, 15 aromatic H); .sup.13C NMR (125 MHz, DMSO-d.sub.6): δ 114.7, 114.8, 117.1, 117.1, 117.2, 117.3, 125.8, 128.8, 128.9, 129.0, 129.8, 131.9, 132.0, 133.2, 133.3, 135.1, 163.7, 165.1, 169.0, 169.9; HRMS for C.sub.23H.sub.15F.sub.2O.sup.+ ([M].sup.+): 345.1092.

Example 17

Preparation of 2-phenyl-4,6-di(thiophen-3-yl)pyryliumtetrafluoroborate [B17]

(31) 3 eq. of BF.sub.3OEt.sub.2 (97.93 mg, 0.08 ml, 0.69 mmol), dissolved in 1 ml of cyclohexane is added to the mixture of phenyl acetylene (69.65 mg, 0.68 mmol), and Compound A17 ((E)-1,3-di(thiophen-3-yl)prop-2-en-1-one), prepared by the method described by (T. M. Kadayat, C. Park, K. Y. Jun, T. T. Magar, G. Bist, H. Y. Yoo, Y. Kwon and E. S. Lee, Bioorg. Med. Chem., 2015, 23, 3499) (50 mg, 0.23 mmol) in dry cyclohexane (2 ml) under the oxygen atmosphere. The solution was stirred for 3 hrs at 60° C. After completion of the reaction, the reaction mixture was poured in to 10 ml of diethyl ether, dissolving the residue in DCM (5 ml), to precipitate the product. The product was filtered and washed with diethyl ether and dried in air. Recrystallization from ethanol afforded the compound 2-phenyl-4,6-di(thiophen-3-yl)pyryliumtetrafluoroborate as black crystals; 70 mg (76%), m.p=219-221° C.; IR (neat, cm.sup.−1): 3106; 2964, 1622 (—C═O+), 1513, 1445, 1264, 1224, 1059, 889, 765; .sup.1H NMR (500 MHz, DMSO-d.sub.6): δ 7.67-9.30 (m, 13 aromatic H); .sup.13C NMR (125 MHz, DMSO-d.sub.6): δ 113.1, 113.8, 126.4, 127.5, 128.3, 129.0, 129.7, 129.9, 132.0, 134.6, 135.3, 136.1, 137.7, 157.9, 165.6, 168.5; HRMS for C.sub.19H.sub.13OS.sub.2.sup.+ ([M].sup.+): 321.0412.

Example 18

Preparation of 2,4,6-tri-p-tolylpyrylium tetrafluoroborate [B18]

(32) 3 eq. of BF.sub.3.OEt.sub.2 (89.42 mg, 0.08 ml, 0.0.63 mmol), dissolved in 1 ml of cyclohexane is added to the mixture of 4-Ethynyltoluene (73.18 mg, 0.63 mmol), and Compound A12 ((E)-1,3-di-p-tolylprop-2-en-1-one), prepared by the method described by (T. M. Kadayat, C. Park, K. Y. Jun, T. T. Magar, G. Bist, H. Y. Yoo, Y. Kwon and E. S. Lee, Bioorg. Med. Chem., 2015, 23, 3499) (50 mg, 0.21 mmol) in dry cyclohexane (2 ml) under the oxygen atmosphere. The solution was stirred for 3 hrs at 60° C. After completion of the reaction, the reaction mixture was poured in to 10 ml of diethyl ether, dissolving the residue in DCM (5 ml), to precipitate the product. The product was filtered and washed with diethyl ether and dried in air. Recrystallization from ethanol afforded the compound 2,4,6-tri-p-tolylpyrylium tetrafluoroborate as yellow crystals; 54 mg (58%), m.p=251-253° C.; IR (neat, cm.sup.−1): 3129, 3039, 2921, 1624 (—C═O+), 1599, 1494, 1256, 1191, 1055, 817, .sup.1H NMR (500 MHz, DMSO-d.sub.6): δ 7.54 8.48 (m, 12 aromatic H), 8.94 (s, 2H); .sup.13C NMR (125 MHz, DMSO-d.sub.6): δ 21.4, 21.4, 113.3, 126.4, 128.5, 129.9, 130.4, 146.1, 146.7, 163.9, 169.3; HRMS for C.sub.26H.sub.23O+([M].sup.+): 351.1749.

Example 19

Preparation of 2-(4-bromophenyl)-4,6-di-p-tolylpyrylium tetrafluoroborate [B19]

(33) 3 eq. of BF.sub.3.OEt.sub.2 (89.42 mg, 0.08 ml, 0.63 mmol), dissolved in 1 ml of cyclohexane is added to the mixture of 1-bromo-4-ethynylbenzene (114.05 mg, 0.63 mmol), and Compound A12 ((E)-1,3-di-p-tolylprop-2-en-1-one), prepared by the method described by (T. M. Kadayat, C. Park, K. Y. Jun, T. T. Magar, G. Bist, H. Y. Yoo, Y. Kwon and E. S. Lee, Bioorg. Med. Chem., 2015, 23, 3499) (50 mg, 0.21 mmol) in dry cyclohexane (2 ml) under the oxygen atmosphere. The solution was stirred for 3 hrs at 60° C. After completion of the reaction, the reaction mixture was poured in to 10 ml of diethyl ether, dissolving the residue in DCM (5 ml), to precipitate the product. The product was filtered and washed with diethyl ether and dried in air. Recrystallization from ethanol afforded the compound 2-(4-bromophenyl)-4,6-di-p-tolylpyrylium tetrafluoroborate as orange crystals; 50 mg (47%), m.p=270-272° C.; IR (neat, cm.sup.−1): 3109, 3030, 2854, 1624 (—C═O.sub.+), 1598, 1498, 1230, 1192, 1055, 1004; .sup.1H NMR (500 MHz, DMSO-d.sub.6): δ 7.61-8.55 (m, 12 aromatic H), 9.09 (s, 2H); .sup.13C NMR (125 MHz, DMSO-d.sub.6): δ 21.4, 21.5, 113.9, 126.2, 128.3, 128.7, 129.1, 129.4, 130.1, 130.2, 130.5, 130.5, 132.8, 146.5, 147.1, 164.2, 168.0, 169.9; HRMS for C.sub.25H.sub.20BrO.sup.+ ([M].sup.+): 415.0645.

Example 20

Preparation of 2-(4-n-propylphenyl)-4,6-di-p-tolylpyrylium tetrafluoroborate [1320]

(34) 3 eq. of BF.sub.3.OEt.sub.2 (89.42 mg, 0.08 ml, 0.63 mmol), dissolved in 1 ml of cyclohexane is added to the mixture of 1-ethynyl-4-propylbenzene (91.21 mg, 0.63 mmol), and Compound A12 ((E)-1,3-di-p-tolylprop-2-en-1-one), prepared by the method described by (T. M. Kadayat, C. Park, K. Y. Jun, T. T. Magar, G. Bist, H. Y. Yoo, Y. Kwon and E. S. Lee, Bioorg. Med. Chem., 2015, 23, 3499) (50 mg, 0.21 mmol) in dry cyclohexane (2 ml) under the oxygen atmosphere. The solution was stirred for 3 hrs at 60° C. After completion of the reaction, the reaction mixture was poured in to 10 ml of diethyl ether, dissolving the residue in DCM (5 ml), to precipitate the product. The product was filtered and washed with diethyl ether and dried in air. Recrystallization from ethanol afforded the compound 2-(4-propylphenyl)-4,6-di-p-tolylpyrylium tetrafluoroborate as orange crystals; 53 mg (54%), m.p 252-254° C.; IR (neat, cm.sup.−1): 3114, 3039, 2928 (—C═O+), 2869, 1625, 1600, 1496, 1273, 1055, 818; .sup.1H NMR (500 MHz, DMSO-d.sub.6): δ 0.95 (t, 3H, —CH.sub.3), 1.69 (st, 2H, —CH.sub.2), 2.75 (t, 2H, —CH.sub.2), 7.58-8.52 (m, 12 aromatic H), 9.00 (s, 2H); .sup.13C NMR (125 MHz; DMSO-d.sub.6): δ 13.6, 21:4, 21.4, 23.6, 37.2, 113.2, 113.3, 126.3, 126.6, 128.5, 128.6, 129.4, 129.8, 129.9, 130.4, 146.1, 146.7, 150.4, 163.8, 169.3; HRMS for C.sub.28H.sub.25O.sup.+ ([M].sup.+): 379.2056. Found: 379.2055.

Example 21

Preparation of 2-(4-fluorophenyl)-4,6-di-p-tolylpyrylium tetrafluoroborate [B21]

(35) 3 eq. of BF.sub.3.OEt.sub.2 (89.42 mg, 0.08 ml, 0.63 mmol), dissolved in 1 ml of cyclohexane is added to the mixture of 1-ethynyl-4-fluorobenzene (76.19 mg, 0.63 mmol), and Compound A12 ((E)-1,3-di-p-tolylprop-2-en-1-one), prepared by the method described by (T. M. Kadayat, C. Park, K. Y. Jun, T. T. Magar, G. Bist, H. Y. Yoo, Y. kwon and E. S. Lee, Bioorg. Med. Chem.; 2015, 23, 3499) (50 mg, 0.21 mmol) in dry cyclohexane (2 ml) under the oxygen atmosphere. The solution was stirred for 3 hrs at 60° C. After completion of the reaction, the reaction mixture was poured in to 10 ml of diethyl ether, dissolving the residue in DCM (5 ml), to precipitate the product. The product was filtered and washed with diethyl ether and dried in, air. Recrystallization from ethanol afforded the compound 2-(4-fluorophenyl)-4,6-di-p-tolylpyrylium tetrafluoroborate as orange crystals; 41 mg (44%), m.p.=242-244° C.; IR (neat, cm-1): 2968, 2922, 1626 (—C═O+), 1599, 1492, 1348, 1194, 1165, 1055, 845; .sup.1H NMR (500 MHz, DMSO-d.sub.6): δ 7.61-9.05 (m, 14 aromatic H); .sup.13C NMR (125 MHz, DMSO-d.sub.6): 21.4, 21.4, 113.5, 113.6, 117.0, 117.2, 125.8, 126.3, 128.7, 129.4, 130.0, 130.4, 130.5, 131.6, 131.7, 146.3, 146.9, 164.2, 164.9, 168.1, 169.7; HRMS for C.sub.25H.sub.20FO.sup.+ ([M].sup.+): 355.1501.

Example 22

Preparation of 2-(thiophen-3-yl)-4,6-di-p-tolylpyrylium tetrafluoroborate [B22]

(36) 3 eq. of BF.sub.3.OEt.sub.2 (89.42 mg, 0.08 ml, 0.63 mmol), dissolved in 1 ml of cyclohexane is added to the mixture of 3-ethynylthiophene (68.46 mg, 0.63 mmol), and Compound A12 ((E)-1,3-di-p-tolylprop-2-en-1-one), prepared by the method described by (T. M. Kadayat, C. Park, K. Y. Jun, T. T. Magar, G. Bist, H. Y. Yoo, Y. Kwon and E. S. Lee, Bioorg. Med. Chem., 2015, 23, 3499) (50 mg, 0.21 mmol) in dry cyclohexane (2 ml) under the oxygen atmosphere. The solution was stirred for 3 hrs at 60° C. After completion of the reaction, the reaction mixture was poured in to 10 ml of diethyl ether, dissolving the residue in DCM (5 ml), to precipitate the product. The product was filtered and washed with diethyl ether and dried in air. Recrystallization from ethanol afforded the compound 2-(thiophen-3-yl)-4,6-di-p-tolylpyrylium tetrafluoroborate as black colour crystals; 89 mg (98%), m.p=232-234° C.; IR (neat, cm.sup.−1): 3108, 2920, 2851, 1625 (—C═O+), 1599, 1495, 1266, 1193, 1057, 817; .sup.1H NMR (500 MHz, DMSO-d.sub.6): δ 7.60-9.26 (m, 14 aromatic H); .sup.13C NMR (125 MHz, DMSO-d.sub.6): δ 21.4, 21.4, 112.9, 113.6, 126.3, 128.6, 129.5, 129.8, 130.4, 130.5, 132.1, 146.0, 146.6, 0.164.1, 165.2, 168.8; HRMS for C.sub.23H.sub.16OS.sup.+ ([M].sup.+): 343.1164.

Example 23

Preparation of 2,4,6-triphenylpyrylium trifluoromethanesulfonate [D1]

(37) 3 eq. of HOTf (108.06 mg, 0.06 ml, 0.72 mmol), is added to the mixture of phenyl acetylene (74 mg, 0.72 mmol), and Compound A1 (E-Chalcone), prepared by the method described by T. M. Kadayat, C. Park, K. Y. Jun, T. T. Magar, G. Bist, H. Y. Yoo, Y. Kwon and E. S. Lee, Bioorg. Med. Chem., 2015, 23, 3499) (50 mg, 0.24 mmol) in dry cyclohexane (2 ml) under the oxygen atmosphere. The solution was stirred for 3 hrs at 60° C. After completion of the reaction, the reaction mixture was poured in to 10 ml of diethyl ether dissolving the residue in DCM (5 ml), to precipitate the product. The product was filtered and washed with diethyl ether and dried in air. Recrystallization from ethanol afforded the compound 2,4,6-triphenylpyrylium trifluoromethanesulfonate as yellow crystals; 53 mg (48%), m.p=252-254° C.; IR (neat, cm.sup.−1): 2920, 2851, 1622, (—C═O+), 1594, 1499, 1471, 1254, 1144, 1031, 770, 641; .sup.1H NMR (500 MHz, DMSO-d6): δ 7.79-8.94 (m, 15 aromatic H), 9.19 (s, 2H); .sup.13C NMR (125 MHz, DMSO-d6): 115.7, 129.3, 129.6, 130.3, 130.4, 130.5, 132.9, 135.5, 135.7, 165.6, 170.6; HRMS C.sub.23H.sub.17O.sup.+ ([M].sup.+): 309.1278.

Example 24

Preparation of 2,4-diphenyl-5,6-dihydrobenzo[h]chromen-1-ium tetrafluoroborate [D2]

(38) 3 eq. of BF.sub.3.OEt.sub.2 (89.42 mg, 0.08 ml, 0.63 mmol), dissolved in 1 ml of cyclohexane is added to the mixture of phenyl acetylene (64.45 mg, 0.63 mmol), and Compound C1 ((E)-2-benzylidene-3,4-dihydronaphthalen-1(2H)-one), prepared by the method described by (T. M. Kadayat, C. Park, K. Y. Jun, T. T. Magar, G. Bist, H. Y. Yoo, Y. Kwon and E. S. Lee, Bioorg. Med. Chem., 2015, 23, 3499) (50 mg, 0.21 mmol) in dry cyclohexane (2 ml) under the oxygen atmosphere. The solution was stirred for 3 hrs at 60° C. After completion of the reaction, the reaction mixture was poured in to 10 ml of diethyl ether, dissolving the residue in DCM (5 ml), to precipitate the product. The product was filtered and washed with diethyl ether and dried in air. Recrystallization from ethanol afforded the compound name as yellow crystals; 43 mg (48%), m.p=248-250° C.; IR (neat, cm-1): 3066, 2851, 1612 (—C═O+), 1596, 1493, 1386, 1243, 1053, 881, 728; .sup.1H NMR (500 MHz, DMSO-d.sub.6): δ 3.09 (t, 2H, —CH.sub.2), 3.25 (t, 2H, —CH.sub.2), 7.59-8.55 (m, 14 aromatic H), 8.84 (s, 1H); .sup.13C NMR (125 MHz, DMSO-d.sub.6): δ 24.2, 25.7, 119.1, 125.9, 126.8, 128.4, 128.4, 128.8, 128.9, 129.2, 129.3, 129.4, 129.9, 132.1, 134.0, 1347, 135.6, 142.0, 165.8, 166.6, 167.4; HRMS for C.sub.25H.sub.19O.sup.+ ([M].sup.+): 335.1435; HRMS for C.sub.25H.sub.19O.sup.+ ([M].sup.+): 335.1435.

ADVANTAGES OF THE INVENTION

(39) The various advantages of the present process are given below. 1. The present invention provides an industrially viable and cost effective process for the preparation of symmetrical and unsymmetrical pyrylium salts. 2: In the present invention, we have developed a four component, two-step process for the synthesis of variety of symmetrical and unsymmetrical pyrylium salts. 3. The process is conducted under the oxygen atmosphere; there are no side products observed which apparently improved the yields of the products.