Novel syntheses of naphthoquinone methide near-infrared dyes

摘要

J. CHEM. SOC. PERKIN TRANS. I 1988 Novel Syntheses of Naphthoquinone Methide Near-infrared Dyes Yuji Kubo," Fuji0 Mori, Keiko Komatsu, and Katsuhira Yoshida Department of Chemistry, Faculty of Science, Kochi University, Akebono-cho, Kochi 780,Japan A novel type of naphthoquinone methide near-i.r. dye has been synthesized by condensing 1-naphthyl-ma lonon itri le or 1-nap ht hylcyanoacetamide with p-N,N-d ialky lami noan iIines in the presence of an oxidizing agent under alkali conditions. These dyes can absorb near-i.r. light at 722-761 nm. A dye film of 4-(4-diethylamino-2-methylphenylimino) -1,4-dihydronaphthyIidenemalononitrile showed a A,,,,,. value of 785 nm and reflected 23.3 of the incident light intensity at 830 nm; these properties make the compound a potential diode-laser optical storage medium.Near4.r. absorbing dyes have been developed for use as optical information recording media for gallium-aluminium-arsenic (GaAlAs) diode-lasers.' Since the latter emit near4.r. light at 800-830 nm, the dyes used for optical recording have to absorb in this range. Although a small number of chromophoric systems have been prepared to absorb near4.r. light,* naphthoquinone methide dyes have, until now, not been among them. Earlier,3 we suggested that the novel deep-coloured naphthoquinone methide dyes (I), the first absorption band for R3 (I 1 which is caused by the intramolecular charge-transfer character of the transition, would, upon introduction of an electron- accepting group (A,A') such as cyano group in the methylene segment and electron-donating group such as alkylamino group in the phenyl ring, undergo a bathochromic shift and thence absorb the near-i.r.light. Here, we report the syntheses of such systems by condensing 1 -naphthylmalononitrile (la) or 1-naphthylcyanoacetamide CN R3 A xHCl yH,SO, zH20 (1) (2 1 a;A = CN a;R' = R2 = Et, R3= Me, x = 1 b; A = CONH, b; R' = R2 = Me, R3 = H, x =2 C; R' = R2 = Et, R3 = H, y =1 d; R' = Et, RZ = C2H,0H, R3= Me, Y+1 e; R' = Et, RZ= C2H,NHS02Me, R3= Me, y=3/2, z=1 (lb) with p-N,N-dialkylaminoaniline(2) in the presence of an oxidizing agent under alkaline conditions. The film properties of one of these dyes has been examined for use in diode-laser optical storage. Results and Discussion Novel syntheses of 4-(4-diethylamino-2-methylphenylimino)-1,4-dihydronaphthylidenemalononitrile (3a) by condensing 1-naphthylmalononitrile (la) with 2-methyl-4-diethylamino- aniline hydrochloride (2a) in the presence of an oxidizing agent under alkaline conditions at room temperature for 10 min are summarized in Table 1 (runs 1-6).The reaction was promoted by the following oxidizing agents in the order: sodium hypochlorite potassium dichromate 2 ammonium peroxy- disulphate potassium ferricyanide (runs 3-6). The yield of (3a) also depended on the amount of (2a) and on the oxidizing agent (runs 1-3). A 5 1 yield of (3a) was obtained in the case of run 3. Reaction of (la) with p-N,N-dimethylaminoaniline dihydrochloride (2b) under similar conditions and in the presence of sodium hypochlorite gave the naphthylidene-malononitrile (3b) in 23 yield (run 7). Use of potassium ferricyanide as the oxidizing agent gave an increased (46) yield of (3b) (run 8).From these results, the reaction is considered to proceed by oxidation of the p-N,N-dialkylaminoaniline,uia a semiquinone ion, the ease of formation of which is dependent upon the nature of the oxidizing agent and aniline. Similarly, the derivatives, (k),(3d),and (3e) were obtained in 27,29, and 16 yields respectively (runs 9-1 1). The amide analogue (3f) CN R3oxidizingagent A (3) a;A = CN, R' b; A = CN, R' C; A = CN, R' d; A = CN, R' e; A = CN, R' f; A = CONH,, = R2 = Et, R3 =Me = R2 = Me, R3 = H = R2 =Et, R3 =H = Et, R2=C2H,0H, R3=Me = Et, R2= C2H4NHS02Me, R3= Me R' = R2 = Et, R3 = Me Scheme 1.Reaction of 1-Naphthylmalononitrile (la) or 1-naphthylcyanoacetamide (lb) with p-N,N-dialkylaminoanilines 2440 J. CHEM. SOC. PERKIN TRANS. I 1988 Table 1. Syntheses of naphthoquinone methide derivatives (3)" Table 2. Light absorption properties of (3) Oxidizing Yield h,,,,/nm E,,.J mol-' cm-' Run Substrate Aniline (mol)b agent (mol)' Product ()d DY e (CHCI3) (CHCI,) 1 (la) (2a) 1 NaOCl 2 (3a) 17 (34 761 30 800 2 (la) (2a) 2 NaOCl 2 (3a) 29 (3b) 722 25 500 3 (la) (2a) 2 NaOCl 5 (3a) 51 738 30 800 4 (la) (2a) 2 K,Cr,O, 5 (3a) 36 (3d) 743 24 200 5 (la) (2a) 2 K,Fe(CN), 5 (3a) 23 (3e) 728 28 900 6 (la) (2a) 2 (NH,),S,O, 5 (3a) 34 (30 754 29 400 7 (la) (2b) 2 NaOCl 5 (3b) 23 8 (la) (2b) 2 K,Fe(CN), 5 (3b) 46 9 (la) (2c) 2 NaOCl 5 (3c) 27 Table 3.Effect of solvents on the absorption maxima of (3) 10 (la) (2d) 2 NaOCl 5 (3d) 29 11 (la) (2e) 2 NaOCl 5 (3e) 16 'Lax./nmh12 (lb) (2a) 1 NaOCl 2 (3f) 3 7 "Reactions were carried out under room temperature for 10 min. Solvent (3a) (3b) (3c) (3d) (3e) (30 Molar ratio: 2/1. Molar ratio: Oxidizing agent/l. Yield of Hexane 707 666 683 u U a isolated material after purification. Cyclohexane 714 675 691 703 698 a Benzene 732 695 710 722 706 719 Ethyl acetate 742 700 716 743 727 719 Chloroform 76 1 722 738 743 728 759 synthesized by the reaction of (lb) with (2a) was obtained in Ethanol 762 729 750 766 753 756 very low yield (run 12), many side products being produced Dimet hylformamide 779 731 751 778 762 752 which made the isolation of the pure dye difficult. a Too insoluble.0xiditing may be explained in terms of the instability of the amide entity, agent which underwent many side reactions. ___) Absorption Spectra of'the Dyes (3).-The absorption spectra of these dyes (3) were measured in chloroform (see Table 2). The L dye (3a) is green, absorbs near-i.r. light at 761 nm 30 800) ( IId in chloroform, and produces a large bathochromic shift of 145 nm in comparison with the A,,,, of the corresponding indoaniline dye 4-(4-diethylamino-2-methylphenylimino)-1,4-naphthoquinone.6 Introduction of the dicyano groups as an electron acceptor into the methylene segment causes a large bathochromic shift of the absorption band. As shown in Table 2, the first absorption band of each dye is also dependent on the strength of the electron-donating power of the aminophenyl ring. In particular, the introduction of a 2-methyl group into (m)A = CN, CONHZ (3c) produced a 23 nm red shift dye (3a)I.In contrast, the corresponding amide derivative (3f) absorbs near-i.r. light at 754 nm (cmaX,29400) in chloroform and produced a 7 nm hypsochromic shift in comparison with the h,,,, of (3a). All these dyes (3) showed intense absorption bands in the near4.r. region. The effect of solvents on the absorption maxima of (3) are listed in Table 3. The absorption maxima of the dyes (3) shifted NC -2A C I NR' R*NRW (31 N Scheme 2.Scheme 2 illustrates a possible reaction path. First, oxidation of the p-N,N-dialkylaminoaniline(I) produces a semiquinone ion which, stabilized by the resonance (IIa) +--+(IIb), reacts with the carbanion of substrate (111) to give the leuco dye (IV); this is then oxidized to yield (3). The low reactivity of (3) 1-naphthylcyanoacetamide (1b) in the dye-forming reaction Scheme 3. J. CHEM. SOC. PERKIN TRANS. I 1988 2441 (CD,),SO 6.62 (1 H, s, CH) and 7.35-8.02 (7 H, m, ArH); 1-naphthylcyanoacetamide(lb) (64), m.p. 193-194 "C (lit.,' 193-194 "C). p-N,N-Dialkylaminoanilineswere reagent grade and were used without further purification. General Procedure for the Preparation of the Substituted Naphthylidene Nitriles (3a--f).-An aqueous solution of an oxidizing agent (4 or 10 mmol) at room temperature was added dropwise to an aqueous NaOH solution of (la) (2 mmol) and (2) (2 mmol or 4 mmol).The mixture was stirred for 10 min at room temperature after which the product was filtered off, dried, and chromatographed on silica gel (Wacogel C-300) using chloroform or hexane+thyl acetate mixture as an eluant. The dyes (3a4) were recrystallized from ethanol. The reaction of (lb) and (2a) was carried out in the same manner. The reaction mixture was chromatographed on alumina activated (Wako ca.300 mesh) using chloroform as an eluant and recrystallized from benzene. Details of the actual conditions used are given in Table 1.4-(4-Diethylamino-2-methylpheny1imino)-1,4-dihydro-nuphthylidenemalononitrile (3a), m.p. 135-1 36 "C; 600 8 00 1000 h,,,,(CHCl,)(amp;,,,,761 nm 30 800 dm3 mol-I cm-'); ?i,(CDCl,) h/nm Figure. Absorption and reflection spectra for a 60 nm-thick film of (3a) to longer wavelength with an increase in solvent polarity. For example, the dye (3a) showed a A,,,. value of 707 nm in hexane. A bathochromic shift of 72 nm, positive solvatochromism, was observed for the dye (3a) in going from hexane to dimethyl- formamide. From these results, it was recognized that the dyes (3) have significant polar structure, (3'), in the excited state (Scheme 3). In the case of (3f), however, the small negative solvatochromism observed in going from chloroform to dimeth ylformamide, may be explained in terms of stabilization of (3f) by polar solvents in the ground state. Prepurution qf'u Film of the Dye (3).--Since these dyes have potential for use in diode-laser optical storage, we investigated their film properties. In the spin-coating process used to prepare a dye film, it is necessary, in order to obtain a smooth homogeneous layer, that the dye should have a good solubility in the solvent used.As shown in Table 3, in general, the dyes (3) have better solubility in the following order: (3a-c) (3d-e) (3f). A film of (3a) was thought likely to be best for investigating film properties, and the Figure shows absorption and reflection spectra for such a 60 nm-thick dye film prepared by solvent coating on to pol y(me th ylme t hacry late).The absorption spectrum of the film of (3a) exhibited a broad peak at a wavelength of 600-1 OOO nm and a A,,,. value of 785 nm which produced a bathochromic shift of 24 nm in comparison with that of (3a) in chloroform. The film reflected 23.3 of incident light intensity at 830 nm. These properties suggest that it has potential as a diode-laser optical storage medium. Experimental M.p.s are uncorrected. Absorption spectra were measured using a Hitachi 220A spectrophotometer. ' H N.m.r. spectra were taken on a Hitachi R-90H spectrometer. Mass spectra were run on a Hitachi M-80B spectrometer, and elemental analyses were obtained using a Perkin-Elmer 240C C,H,N, analyser.Materials.-The following compounds were synthesized by the method described in the literature: 1-naphthylmalononitrile (la) (74), m.p. 167-168 "C (lit.: 166-167 "C); G,CDCl,- 1.24 (6 H, t, 2 x CH,), 2.43 (3 H, s, CH,), 3.44 (4 H, q, 2 x CH,), 6.62-6.71 (3 H, m, ArH), 7.28 (1 H, d, J 9.8 Hz, quinonoid H), 7.51 (1 H, d, J9.8 Hz, quinonoid H), 7.6G7.69 (2 H, m, ArH), and 8.67-8.90 (2 H, m, ArH); m/z 366 (M+)and 351 (M+ -15) (Found: C, 78.9; H, 5.8; N, 15.4. C,,H,,N, requires C, 78.7; H, 6.05; N, 15.3). 4-(4-Dimethy1aminophenylimino)-1,4-dihydronuph thylidene- mulononitrile (3b), m.p. 181-183 "C; h,,,, (CHCl,) 722 nm (E,,,,~, 25 500 dm3 mol-' cm-'); GH(CDC1,) 3.06 (6 H, s, 2 x CH,), 6.75 (2 H, d, J 9.0 Hz, ArH), 7.05 (2 H, d, J 9.0 Hz, ArH), 7.21 (1 H, d, J9.8 Hz, quinonoid H), 7.42 (1 H, d, J9.8 Hz, quinonoid H), 7.52-7.62 (2 H, m, ArH), and 8.54-8.79 (2 H, m, ArH); mjz 324 (M+),309 (M+ -15), and 280 (M+ -44) (Found: C, 77.8; H, 5.0; N, 17.3.C,,HI6N4 requires C, 77.25; H, 4.5; N, 17.4). 4-(4 -Diet hj,lam inop hen y lim ino) -1,4-dih y dr onaph thylidene-mulonotrile (3c), m.p. 14amp;141 "C; Amax(.(CHC1,) 738 nm (q,,,,. 30 800 dm3 mol-' cm-'); 6,CDC13 + (CD,),SO 1.25 (6 H, t, 2 x CH,),3.47 (4 H,q,2 x CH,),6.75 (2 H,d,J9.2 Hz, ArH), 7.10 (2 H, d, J 9.2 Hz, ArH), 7.26 (1 H, d, J 10.1 Hz, quinonoid H), 7.52 (1 H, d, J 10.1 Hz, quinonoid H), 7.63-7.73 (2 H, m, ArH), and 8.65-8.91 (2 H, m, ArH) (Found: C, 78.0; H, 5.8; N, 15.4; M+,353. C,,H,,N, requires C, 78.4; H, 5.7; N, 15.9; M, 353.4-{ 4'- Ethyl-( 2-hydroxyethy1)amino) -2-methylphen y 1 imino)-1,4-dihydronaphthylidenemalononitrile(3d), m.p. 182- 183 "C; h,,,.(CHCl,) 743 nm (q,,,,, 24 200 dm3 mol-' cm-'); G,CDCl, + (CD,),SO 1.235 (3 H, t, CH,), 2.42 (3 H, s, CH,), 3.41-3.98 (7 H, m), 6.62-6.78 (3 H, m, ArH), 7.23 (1 H, d, J 10.1 Hz, quinonoid H), 7.52 (1 H, d, J 10.1 Hz, quinonoid H), 7.61-7.75 (2 H, m, ArH), and 8.67-8.90 (2 H, m, ArH) (Found: C, 74.9; H, 5.9; N, 14.4; M', 383. C,,H,,N,O requires C, 75.4; H, 5.8; N, 14.7; M, 383). 4-(4'-Ethyl-(2-mesylaminoethyl)amino-2-methyl-phenylimino)-1,4-dihydronaphthylidenemalononitrile (3e), m.p. 174-175 "C; h,,,.(CHCl,) 728 nm 28 900 dm3 mol-' cm"); ?i,CDCl, + (CD,),SO 1.23 (3 H, t, CH,), 2.40 (3 H, S, CH,), 2.95 (3 H,s,SO,CH,), 3.26-3.58 (6 H,m), 6.25 (1 H,s, NH), 6.66-6.76 (3 H, m, ArH), 7.20 (1 H, d, J 10.1 Hz, quinonoid H), 7.52 (1 H, d, J 10.1 Hz, quinonoid H), 7.61-7.74 (2 H, m, ArH), and 8.66-8.89 (2 H, m, ArH) (Found: C, 65.3; H, 5.6; N, 15.0; M+,459.C25H,5N5S0, requires C, 65.4; H, 5.45; N, 15.25; M, 459). 4-(4-Diethylamino-2-methy1phenylimino)-1,4-dihydro-naphthylidene(carbamoy1)acetonitrile (3f), m.p. 232-233 "C; h,,,,(CHCl,) 754 nm 29 400 dm3 mol-I cm-') (Found: C, 73.0;H, 5.6;N,13.9;M', 384.C,,H,,N,O requires C, 75.0;H, 6.3;N,14.6; M, 384). Preparation of 4-(4-Diethylamino-2-methylpheny1imino)-1,4-naphthoquinone.-The known title compound was synthesized by condensing 1 -naphthol with 4-diethylamino-2-methylaniline hydrochloride; it had m.p.114-1 15 "C (lit.,6 114"C); hm,,.(CHCl,) 616nm 16 500 dm3 mol-' cm-I); G,(CDCI,) 1.20 (6 H, t, 2 x CH,), 2.37 (3 H, s, CH,), 3.42 (4 H, q, 2 x CH,), 6.37-6.58 (3 H, m, ArH), 6.54 (1 H, d, J 10.5Hz, quinonoid H), 7.36(1 H,d, J 10.2Hz, quinonoid H),7.43-7.64 (2H,m,ArH),8.02(1H,dd,J6.8and2.3Hz,ArH),and8.40(1H,dd, J 6.2and 2.1 Hz, ArH). Preparation of the Film of the Dye (3a).-The dye (3a) (7.0 mg) was dissolved in tetrachloroethane (700 mg), and the solution filtered through a 0.22 pm filter. The filtrate was dropped onto a poly(methy1 methacrylate) (PMMA) substrate, and coated by a spinner method at a rotational speed of 800 revolution min-I. The coating layer was dried at 60 "C for ca.5 min to give an approximately 60 nm-thick dye film of (3a). The absorption and the reflection spectra of this dye film were recorded on a 323 Hitachi Recording Spectrophotometer. J. CHEM. SOC. PERKIN TRANS. I 1988 Acknowledgements The authors thank the Advanced Instrumentation Center for Chemical Analysis, Ehime University and University of Osaka Prefecture for mass spectral and elemental analyses. The author also expresses his sincere thanks to Mr. S. Maeda of the Research Center, Mitsubishi Chemical Industries Limited for determination of the optical properties of the dye film. References 1 M. Umehara, M. Abe, and H. Oba, Yuki Gosei Kagaku Kyokai Shi, 1985, 43, 334. 2 M. Matsuoka, Senryo To Yakuhin, 1985, 30, 308. 3 Y. Kubo, F. Mori, and K. Yoshida, Chem. Lett., 1987, 1761. 4 J. K. Williams, E. L. Martin, and W. A. Sheppard, J.Org. Chem., 1966, 31, 919. 5 S. Wideqvist (Chem. Abstr., 1948, 42, 6349). 6 A. P. Lurie, G. H. Brown, J. R. Thirtle, and A. Weissberger, J. Am. Chem. Soc., 1961, 83, 5015. Received 4th January 1988;Paper 8/00043C