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Synlett 2002(10): 1617-1620
DOI: 10.1055/s-2002-34226
LETTER
© Georg Thieme Verlag Stuttgart · New York

New Synthetic Approach to Aminosquarylium Cyanine Dyes

L. V. Reisa, J. P. C. Serranoa, P. Almeidab, P. F. Santos*a
a Departamento de Química, Universidade de Trás-os-Montes e Alto Douro, Apartado 1013, 5001-911 Vila Real, Portugal
Fax: +351(259)350480; e-Mail: psantos@utad.pt;
b Departamento de Química e Unidade de Materiais Têxteis e Papeleiros, Universidade da Beira Interior, Rua Marquês d’Ávila e Bolama, 6201-001 Covilhã, Portugal
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Publikationsverlauf

Received 29 July 2002
Publikationsdatum:
23. September 2002 (online)

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Abstract

A novel synthesis of aminosquarylium cyanine dyes, based on the methylation of readily available squarylium dyes with methyl triflate, followed by nucleophilic substitution with appropriate aliphatic amines, was disclosed. By this procedure several new aminosquarylium cyanine dyes bearing benzothiazole, benzoselen­azole and quinoline nuclei were prepared.

Key words

aminosquarylium dyes - squaraines - pentamethine­cyanines - dicarbocyanines - heterocycles

    References and Notes

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  • 11a

    General procedure for the preparation of aminosquarylium dyes 8: Crude 7, prepared as described above, was re-dissolved in anhyd CH2Cl2 (40 mL), under N2 atmosphere, and a 4-fold excess of methylamine was added. After being stirred at r.t. for 30 min, the reaction mixture was washed with cold water and the organic layer was separated by decantation and dried over anhyd Na2SO4. The solvent was removed under reduced pressure and the resulting residue was recrystallized from CH2Cl2-MeOH-Et2O

  • 11b

    General procedure for the preparation of amino-squarylium dyes 9: To a untreated solution of 7 in dry CH2Cl2, prepared as described above, vigorously stirred under N2 atmosphere at r.t., was added a 5-fold excess of N,N-diethylamine. After 3-5 h the reaction mixture was worked-up as described for the preparation of O-methylsquarylium dyes 7 and the resulting residue was recrystallized from CH2Cl2-MeOH-Et2O (Table [1] ).

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9

General procedure for the preparation of O-methylated squarylium dyes 7: To a solution of 6 (ca. 0.4 mmol) in anhyd CH2Cl2 (50 mL), vigorously stirred under N2 atmosphere at r.t., was added a 4-fold excess of CF3SO3CH3. After 3-5 h, the reaction mixture was quenched with cold 5% aq NaHCO3. The organic layer, after separation by decantation, was dried over anhyd Na2SO4 and the solvent removed under reduced pressure. The resulting residue was recrystallized from CH2Cl2-MeOH-Et2O.

12

General procedure for the replacement of counter-ion in dyes 8 and 9: To a solution of the dye, prepared as described, in MeOH, at r.t., was added an approximately equal volume of 14% aq KI. After 2 h, the precipitated dye was collected by filtration, washed with water and recrystallized from CH2Cl2-MeOH-Et2O.

14

Selected data. Compound 7a: IR (KBr): 1648, 1506, 1427, 1396, 1361, 1311, 1247, 1218, 1157, 1118, 750 cm-1;
1H NMR (400.13 MHz, DMSO-CDCl3): δ 1.36 (6 H, t, J = 7.2 Hz, CH3), 4.44 (4 H, q, J = 7.2 Hz, CH2), 4.51 (3 H, s, OCH3), 5.99 (2 H, s, CH=), 7.36 (2 H, t, J = 8.0 Hz, ArH), 7.52 (2 H, t, J = 8.0 Hz, ArH), 7.64 (2 H, d, J = 8.0 Hz, ArH), 7.91 (2 H, d, J = 8.0 Hz, ArH); 13C NMR (100.62 MHz,

DMSO-CDCl3): δ 12.3 (CH3), 41.4 (CH2), 60.3 (OCH3), 84.6, 113.1, 122.5, 125.0, 127.4, 127.7, 139.8, 157.9, 161.5, 173.5, 176.7; HRMS (FAB): calcd for C25H23N2O2S2 447.120097, found 447.122165. Compound 8a: IR (KBr):


Table 1 The Yield, Melting Point, and UV Spectral Data of Squarylium Cyanine Dyes 6-9 (continued)
Dye X R Yield (%) Mp (ºC) λmax c (nm) Log ε
6a S Et 50 >300 650 5.24
6b S Hex 76 270b 650 5.41
6c Se Et 72 300b 665 5.49
6d Se Hex 74 262b 668 5.41
6e CH=CH Et 45 >300 707 5.39
6f CH=CH Hex 42 287b 710 5.37
7a S Et 81 274b 632 5.27
7b S Hex 87 234b 632 5.23
7c Se Et 76 274b 647 5.28
7d Se Hex 76 249b 650 5.32
7e CH=CH Et 95 289b 671 5.62
7f CH=CH Hex 86 259b 674 5.47
8a S Et 56a 291-292 659 5.23
8b S Hex 75 a 251-252 659 5.22
8c Se Et 44a 297b 674 5.26
8d Se Hex 69a 240b 677 5.23
8e CH=CH Et 76a >300 707 5.43
8f CH=CH Hex 82a 260b 710 5.36
9a S Et 62a 283b 668 5.27
9b S Hex 75a 236-238 671 5.33
9c Se Et 56a 284b 686 5.22
9d Se Hex 88a 287b 689 5.26
9e CH=CH Et 89a 282b 719 5.55
9f CH=CH Hex 84a 242b 722 5.38
a From the corresponding squarylium dye 6. b With decomposition.
c Measured in MeOH/CH2Cl2 (99:1).

3438, 1633, 1560, 1455, 1428, 1353, 1309, 1251, 1228, 1110, 746 cm-1; 1H NMR (250.13 MHz, DMSO-CDCl3): δ 1.42-1.49 (6 H, m, CH3), 3.36 (3 H, d, J = 5.0 Hz, NCH3, collapses to s with D2O), 4.31-4.41 (4 H, m, CH2), 5.95 (1 H, s, CH=), 6.35 (1 H, s, CH=), 7.28-7.51 (6 H, m, ArH), 7.65-7.74 (2 H, m, ArH), 8.63 (1 H, br, NH, exchangeable with D2O); 13C NMR (100.62 MHz, DMSO-CDCl3): δ 10.7 (CH3), 10.9 (CH3), 28.8 (NCH3), 39.5 (CH2), 40.0 (CH2), 84.5, 84.6, 110.8, 111.2, 120.7, 121.0, 122.8, 123.3, 125.9, 126.1, 126.3, 138.5, 138.6, 156.0, 159.4, 162.6, 171.9; HRMS (FAB): calcd for C25H24N3OS2 446.136081, found 446.137251. Compound 9a: IR (KBr): 1621, 1544, 1421, 1357, 1313, 1214, 1149, 1116, 1008, 775 cm-1; 1H NMR (400.13 MHz, DMSO-CDCl3): δ 1.00-1.04 (12 H, m, CH3), 3.28 (4 H, q, J = 7.2 Hz, CH2), 3.92 (4 H, q, J = 7.3 Hz, CH2), 5.40 (2 H, s, CH=), 6.92 (2 H, t, J = 7.2 Hz, ArH), 7.03-7.10 (4 H, m, ArH), 7.26 (2 H, d, J = 7.6 Hz, ArH); 13C NMR (100.62 MHz, DMSO-CDCl3): δ 11.4 (CH3), 14.4 (CH3), 40.8 (CH2), 45.6 (CH2), 84.9 (CH=), 111.7, 121.3, 124.3, 127.0, 127.2, 139.1, 155.4, 159.6, 160.9, 173.1; HRMS (FAB): calcd for C28H30N3OS2 488,183031, found 488,185052.