Copper chloride-catalyzed efficient three-component one-pot synthesis of carbamatoalkyl naphthols under solvent-free conditions

Transcription

1 Indian Journal of Chemistry Vol. 53B, June 2014, pp Copper chloride-catalyzed efficient three-component one-pot synthesis of carbamatoalkyl naphthols under solvent-free conditions Zhiguo Song*, Lianli Liu, Xiaohu Sun & Yan Cui Management Center for Experiments, Bohai University, Jinzhou , P. R. China Received 4 December 2012; accepted (revised) 24 January 2014 A highly efficient synthesis of carbamatoalkyl naphthols by a one-pot three-component condensation of 2-naphthol, aldehydes, and methyl/ethyl/benzyl carbamates in the presence of copper chloride under thermal solvent-free conditions has been performed. The suitable solvent, amounts of raw materials and catalyst, and reaction temperature were investigated. Experimental results show that only 1 mol% catalyst was enough to induce the conversion. All new products were characterized by mp, IR, 1 H NMR, 13 C NMR and mass spectrum. A mechanism to rationalize the reaction was proposed. Keywords: Three-component reaction, carbamatoalkyl naphthols, copper chloride, one-pot synthesis, solvent-free Carbamate skeletons are important blocks for natural products and versatile precursors for the synthesis of pharmaceuticals such as mitomycin 1,2, saxitoxin 3, and bleomycin 4. The preparation of carbamate derivatives has attracted considerable attention. Meanwhile, compounds containing 1,3-amino-oxygenated functional groups are frequently found in biologically active natural products and potent drugs such as nucleoside antibiotics and HIV protease inhibitors 5-7. Therefore, carbamatoalkyl naphthols are of considerable interest because of their promising biological and pharmaceutical activities. Despite their importance comparatively few methods for the preparation of 1-carbamatoalkyl-2- naphthol derivatives have been reported. The reported catalysts mainly include triethylbenzylammonium chloride 8, SiO 2 -NaHSO 4 (Ref. 9), Brønsted-acidic ionic liquids 10, silica-supported polyphosphoric acid 11, silica-supported preyssler nano particles 12, SiO 2 -HClO 4 (Ref. 13), zwitterionic type molten salt 14, [MeC(OH) 2 ] + - ClO 4 (Ref. 15), ionic liquid [NMP] + HSO - 4 (Ref. 16), sulfamic acid functionalized magnetic nanoparticles 17, and Mg(OOCCF 3 ) 2 (Ref. 18), etc. Many of them suffer from at least one of the following disadvantages such as low yields, expensive catalyst, higher reaction temperature (>100 C), and a large excess of reagents and catalysts (10 mol%). Therefore, it is necessary to develop a more universal method for the synthesis of carbamatoalkyl naphthols. In this communication, we reported a mild and effcient strategy for preparing 1-carbamatoalkyl-2-naphthols 4 from 2-naphthol 1, aldehydes 2, and carbamtes 3 at a short reaction time and with excellent yields using CuCl 2 2H 2 O as a catalyst (Scheme I). It was found that only 1 mol% CuCl 2 2H 2 O can catalyze the conversion efficiently. Most important, CuCl 2 2H 2 O is inexpensive and easily available. Results and Discussion In order to investigate the optimal conditions, the condensation of 2-naphthol, 2-nitrobenzaldehyde and methyl carbamate was selected as a model reaction. The results were summarized in Table I. The effects of solvent on the yields were investigated. Among the tested solvents such as H 2 O, EtOH, MeCN, and solvent-free media, condensation proceeds more efficient under solvent-free conditions (entry 4). Excess carbamate facilitates the reaction, and 1 mol% catalyst is enough to induce the conversion (entry 8). Reaction temperature affects the reaction significantly and 70 C is suitable. Increasing the temperature further does not lead to better yields. A control experiment without catalyst was carried out. No product was formed even after 4 hr (entry 12). This indicates that the catalyst is essential for the transformation. Having established the optimized conditions, the scope and efficiency of the procedure for the synthesis of a wide variety of 1-carbamatoalkyl-2- naphthols were explored (Table II). The reaction was extended to aromatic aldehydes and aliphatic aldehydes, which reacted with methyl/ethyl/benzyl carbamates and 2-naphthol. As expected, most

2 SONG et al.: ONE-POT SYNTHESIS OF CARBAMATOALKYL NAPHTHOLS 741 OH + R 1 CHO + NH 2 CO 2 R 2 CuCl 2 2H 2 O (1 mol%) 70 o C, solvent- free R 1 NHCO 2 R 2 OH a-4x Scheme I Table I Optimization of various reaction conditions for the preparation of methyl [(2-nitrophenyl)(2-hydroxynaphthalen-1-yl)methyl] carbamate Entry Solvent n(1):n(2):n(3) Catalyst/mol% Temp. ( C) Time (hr) Yield (%) 1 3 ml H 2 O 1:1: ml EtOH 1:1:1.1 2 Reflux ml MeCN 1:1:1.1 2 Reflux :1: :1: :1: :1: :1: :1: :1: :1: :1: Table II Preparation of 1-carbamatoalkyl-2-naphthols catalyzed by CuCl 2 2H 2 O Entry R 1 R 2 Time/hr Product Yield (%) m.p.. ( C) (Ref) 1 Ph Me 0.4 4a (Ref.12) 2 2-NO 2 C 6 H 4 Me 0.3 4b (Ref.12) 3 3-NO 2 C 6 H 4 Me 0.3 4c (Ref.12) 4 4-NO 2 C 6 H 4 Me 0.4 4d (Ref.12) 5 2-ClC 6 H 4 Me 0.3 4e ClC 6 H 4 Me 0.5 4f (Ref.12) 7 2,4-Cl 2 C 6 H 3 Me 0.5 4g CH 3 C 6 H 4 Me 10 4h trace CH 3 OC 6 H 4 Me 10 4i trace - 10 CH 3 CH 2 Me 10 4j 0-11 Ph Et 0.5 4k (Ref.18) 12 2-NO 2 C 6 H 4 Et 0.5 4l NO 2 C 6 H 4 Et 0.5 4m NO 2 C 6 H 4 Et 0.5 4n ClC 6 H 4 Et 0.5 4o ClC 6 H 4 Et 0.7 4p ,4-Cl 2 C 6 H 3 Et 0.6 4q Ph CH 2 Ph 3.0 4r (Ref.12) 19 2-NO 2 C 6 H 4 CH 2 Ph 1.0 4s NO 2 C 6 H 4 CH 2 Ph 0.7 4t (Ref.12) 21 4-NO 2 C 6 H 4 CH 2 Ph 0.7 4u ClC 6 H 4 CH 2 Ph 2.0 4v ClC 6 H 4 CH 2 Ph 2.0 4w ,4-Cl 2 C 6 H 3 CH 2 Ph 2.0 4x

3 742 INDIAN J. CHEM., SEC B, JUNE 2014 reactions proceeded smoothly and the desired products were obtained in good to excellent yields. Aromatic aldehydes carrying electron-withdrawing groups (-NO 2 and-cl) afforded high yields of products. The position of substituents on the aromatic ring showed no effect on the product yield. Only trace of products were detected when aromatic aldehydes carried electron-donating groups (-CH 3 and-och 3 ). The reaction of aliphatic aldehyde such as propionaldehyde with 2-naphthol and methyl carbamate failed to give any product (entry 10). Beside methyl carbamate, ethyl carbamate and benzyl carbamate reacted efficiently and the desired products were obtained in good yields. The work-up procedure is very straightforward, that is the products were isolated and purified by simple filtration and crystallization from aqueous ethanol. Our protocol avoids the use of dry media during the reaction process, which making it superior to the previous methods. The catalytic activity of CuCl 2 2H 2 O was also compared with some Table III Comparison of different Lewis acids catalysts for the preparation of methyl ((2-nitrophenyl)(2- hydroxynaphthalen-1-yl)methyl) carbamate under the optimized conditions Entry Catalyst Time (hr) Yield (%) 1 CuCl 2 2H 2 O AlCl 3 6H 2 O ZnCl Al(NO 3 ) 3 9H 2 O Bi(NO 3 ) 3 5H 2 O SrCl 2 6H 2 O conventional catalysts such as AlCl 3 6H 2 O, ZnCl 2, Al(NO 3 ) 3 9H 2 O, Bi(NO 3 ) 3 5H 2 O, and SrCl 2 6H 2 O. The experimental results were summarized in Table III, which showed that CuCl 2 2H 2 O is superior to the others. A possible mechanism for this transformation is proposed in Scheme II. As reported in the literature 8, reaction of 2-naphthol with aldehydes in the presence of an acid catalyst is known to give o-qm. The o-qm generated in situ reacted with carbamate to form the 1-carbamatoalkyl-2-naphthol 4. As a Lewis acid, CuCl 2 promoted the reaction. Experimental Section Melting points were determined using a RD-II micromelting point apparatus. Infrared spectra were recorded on a Varian Scimitar 2000 series Fourier Transform instrument. 1 H and 13 C NMR spectra were recorded on an Agilent 400-MR spectrometer in DMSO-d 6 using TMS as an internal standard. Mass spectra were obtained with an Agilent 1100 series LC/MSD VL ESI instrument. Elemental analyses were carried out on a Perkin-Elmer EA 2400II elemental analyzer. General procedure for the synthesis of 1-carbamatoalkyl-2-naphthols, 4: To a mixture of 2-naphthol (5 mmol), an aldehyde (5 mmol), and a carbamate (5.5 mmol), CuCl 2 2H 2 O (0.05 mmol) was added. The reaction mixture was stirred on a preheated water bath at 70 C. After completion of the reaction (monitored by TLC), the reaction mixture was cooled to RT. washed with H 2 O/EtOH (v/v = 1/1), and recrystallized from H 2 O/EtOH (v/v = 2/3). The products were Scheme II

4 SONG et al.: ONE-POT SYNTHESIS OF CARBAMATOALKYL NAPHTHOLS 743 characterized by IR, 1 H NMR, 13 C NMR, LC/MS and elemental analysis. Spectral data for new compounds: Methyl ((2-chlorophenyl)(2-hydroxynaphthalen- 1-yl)methyl) carbamate, 4e: White solid; IR (KBr): 3431, 3221, 1690, 1527, 1341, 1052, 819, 753, 706 cm -1 ; 1 H NMR (400 MHz, DMSO-d 6 ): δ 9.96 (s, 1H, OH), 8.04 (d, J = 8.2 Hz, 1H, NH), 7.86 (d, J = 7.1 Hz, 1H, ArH), 7.77 (dd, J = 17.4, 8.3 Hz, 2H, ArH), 7.52 (d, J = 4.6 Hz, 1H, ArH), 7.40 (dd, J = 12.3, 6.8 Hz, 2H, ArH), 7.26 (d, J = 13.9 Hz, 3H, ArH), 7.16 (d, J = 8.6 Hz, 1H, ArH), 6.91 (d, J = 7.8 Hz, 1H, CH), 3.54 (s, 3H, OCH 3 ); 13 C NMR (100 MHz, DMSO-d 6 ): δ 156.5, 153.9, 139.8, 133.0, 132.9, 130.3, 129.9, 129.7, 129.0, 128.8, 128.7, 127.0, 126.7, 123.3, 122.7, 119.0, 117.4, 51.9, 50.1; MS (ESI): m/z 340 [(M-H) -, 100]; Anal. Calcd for C 19 H 16 NO 3 Cl: C, 66.77; H, 4.72; N, Found: C, 66.60; H, 4.64; N, 4.15%. Methyl ((2,4-dichlorophenyl)(2-hydroxy-naphthalen- 1-yl)methyl) carbamate, 4g: White solid; IR (KBr): 3403, 3260, 1678, 1519, 1062, 874, 753, 718 cm -1 ; 1 H NMR (400 MHz, DMSO-d 6 ): δ 9.97 (s, 1H, OH), 8.02 (d, J = 8.5 Hz, 1H, NH), 7.96 (d, J = 7.8 Hz, 1H, ArH), 7.78 (dd, J = 17.8, 8.4 Hz, 2H, ArH), (m, 4H, ArH), 7.28 (t, J = 7.3 Hz, 1H, ArH), 7.14 (d, J = 8.7 Hz, 1H, ArH), 6.85 (d, J = 8.0 Hz, 1H, CH), 3.55 (s, 3H, OCH 3 ); 13 C NMR (100 MHz, DMSO-d 6 ): δ 156.6, 154.0, 139.3, 133.6, 133.0, 132.3, 131.6, 130.1, 129.1, 129.0, 128.6, 127.0, 126.9, 123.0, 122.8, 119.0, 116.7, 52.0, 49.8; MS (ESI): m/z 375 [(M-H) -, 100]; Anal. Calcd for C 19 H 15 NO 3 Cl 2 : C, 60.66; H, 4.02; N, Found: C, 60.81; H, 4.05; N, 3.64%. Ethyl ((2-nitrophenyl)(2-hydroxynaphthalen-1- yl)methyl) carbamate, 4l: White solid; IR (KBr): 3402, 3277, 1686, 1531, 1334, 1039, 813, 744, 697 cm -1 ; 1 H NMR (400 MHz, DMSO-d 6 ): δ 9.79 (s, 1H, OH), 7.92 (d, J = 8.6 Hz, 1H, NH), (m, 4H, ArH), (m, 2H, ArH), 7.44 (dt, J = 17.0, 6.0 Hz, 2H, ArH), (m, 2H, ArH), 7.05 (d, J = 8.7 Hz, 1H, CH), 4.04 (q, J = 7.0 Hz, 2H, CH 2 ), 1.15 (t, J = 7.0 Hz, 3H, CH 3 ); 13 C NMR (100 MHz, DMSO-d 6 ): δ 156.4, 154.0, 149.0, 136.9, 133.3, 132.5, 130.3, 129.4, 128.9, 128.5, 128.1, 127.0, 124.4, 123.0, 122.8, 118.8, 116.5, 60.5, 48.1, 15.0; MS (ESI): m/z 365 [(M-H) -, 100]; Anal. Calcd for C 20 H 18 N 2 O 5 : C, 65.57; H, 4.95; N, Found: C, 65.70; H, 4.88; N, 7.59%. Ethyl ((3-nitrophenyl)(2-hydroxynaphthalen-1- yl)methyl) carbamate, 4m: White solid; IR (KBr): 3396, 3277, 1679, 1527, 1348, 1045, 808, 752, 701 cm -1 ; 1 H NMR (400 MHz, DMSO-d 6 ): δ (s, 1H, OH), 8.13 (d, J = 8.2 Hz, 1H, NH), 8.07 (d, J = 8.1 Hz, 1H, ArH), 7.98 (d, J = 7.8 Hz, 1H, ArH), 7.82 (t, J = 8.4 Hz, 3H, ArH), 7.64 (d, J = 7.8 Hz, 1H, ArH), 7.56 (t, J = 8.0 Hz, 1H, ArH), 7.44 (t, J = 7.5 Hz, 1H, ArH), 7.31 (t, J = 7.5 Hz, 1H, ArH), 7.23 (d, J = 8.8 Hz, 1H, ArH), 6.97 (d, J = 7.8 Hz, 1H, CH), 4.08 (q, J = 6.8 Hz, 2H, CH 2 ), 1.18 (t, J = 6.8 Hz, 3H, CH 3 ); 13 C NMR (100 MHz, DMSO-d 6 ): δ 156.7, 153.5, 148.1, 145.5, 133.2, 132.3, 130.3, 130.1, 129.1, 128.7, 127.3, 123.5, 123.1, 121.9, 120.9, 118.8, 118.4, 60.7, 50.3, 15.0; MS (ESI): m/z 365 [(M-H) -, 100]; Anal. Calcd for C 20 H 18 N 2 O 5 : C, 65.57; H, 4.95; N, Found: C, 65.69; H, 5.02; N, 7.54%. Ethyl ((4-nitrophenyl)(2-hydroxynaphthalen-1- yl)methyl) carbamate, 4n: White solid; IR (KBr): 3430, 3185, 1686, 1518, 1351, 1050, 821, 739, 708 cm -1 ; 1 H NMR (400 MHz, DMSO-d 6 ): δ (s, 1H, OH), 8.15 (d, J = 8.8 Hz, 2H, ArH), (m, 4H, NH and ArH), 7.49 (d, J = 8.6 Hz, 2H, ArH), 7.43 (t, J = 7.5 Hz, 1H, ArH), 7.30 (t, J = 7.5 Hz, 1H, ArH), 7.23 (d, J = 8.8 Hz, 1H, ArH), 6.97 (d, J = 7.7 Hz, 1H, CH), 4.07 (q, J = 6.7 Hz, 2H, CH 2 ), 1.17 (t, J = 6.7 Hz, 3H, CH 3 ); 13 C NMR (100 MHz, DMSO-d 6 ): δ 156.7, 153.5, 151.2, 146.5, 132.3, 130.3, 129.1, 128.8, 127.6, 127.2, 123.8, 123.2, 123.1, 118.8, 118.4, 60.7, 50.5, 15.0; MS (ESI): m/z 365 [(M-H) -, 100]; Anal. Calcd for C 20 H 18 N 2 O 5 : C, 65.57; H, 4.95; N, Found: C, 65.71; H, 4.89; N, 7.71%. Ethyl ((2-chlorophenyl)(2-hydroxynaphthalen- 1-yl)methyl) carbamate, 4o: White solid; IR (KBr): 3420, 3229, 1686, 1525, 1337, 1051, 821, 752, 706 cm -1 ; 1 H NMR (400 MHz, DMSO-d 6 ): δ (s, 1H, OH), 8.28 (d, J = 8.5 Hz, 1H, NH), (m, 3H, ArH), 7.77 (d, J = 5.9 Hz, 1H, ArH), (m, 5H, ArH), 7.39 (d, J = 8.7 Hz, 1H, ArH), 7.15 (d, J = 8.3 Hz, 1H, CH), 4.22 (q, J = 7.1 Hz, 2H, CH 2 ), 1.36 (t, J = 7.1 Hz, 3H, CH 3 ); 13 C NMR (100 MHz, DMSO-d 6 ): δ 156.1, 153.9, 139.8, 133.0, 132.9, 130.3, 129.9, 129.7, 129.0, 128.8, 128.7, 126.9, 126.8, 123.3, 122.7, 119.0, 117.5, 60.4, 50.0, 15.1; MS (ESI): m/z 354 [(M-H) -, 100]; Anal. Calcd for C 20 H 18 NO 3 Cl: C, 67.51; H, 5.10; N, Found: C, 67.64; H, 5.05; N, 4.01%. Ethyl ((4-chlorophenyl)(2-hydroxynaphthalen- 1-yl)methyl) carbamate, 4p: White solid; IR (KBr): 3424, 3197, 1676, 1517, 1330, 1042, 820, 751, 711 cm -1 ; 1 H NMR (400 MHz, DMSO-d 6 ): δ (s, 1H, OH), 7.93 (d, J = 8.3 Hz, 1H, NH), 7.80 (dd, J = 12.8, 6.8 Hz, 2H, ArH), 7.58 (d, J = 8.2 Hz, 1H, ArH), 7.41 (t, J = 7.3 Hz, 1H, ArH), (m, 6H, ArH), 6.87 (d, J = 8.1 Hz, 1H, CH), 4.05 (q, J = 7.2 Hz, 2H,

5 744 INDIAN J. CHEM., SEC B, JUNE 2014 CH 2 ), 1.17 (t, J = 6.9 Hz, 3H, CH 3 ); 13 C NMR (100 MHz, DMSO-d 6 ): δ 156.6, 153.3, 141.9, 132.3, 131.4, 130.0, 129.0, 128.8, 128.5, 128.3, 127.5, 127.1, 123.6, 123.0, 118.9, 60.7, 50.2, 15.0; MS (ESI): m/z 354 [(M-H) -, 100]; Anal. Calcd for C 20 H 18 NO 3 Cl: C, 67.51; H, 5.10; N, Found: C, 67.39; H, 5.17; N, 3.88%. Ethyl ((2,4-dichlorophenyl)(2-hydroxy-naphthalen- 1-yl)methyl) carbamate, 4q: White solid; IR (KBr): 3412, 3071, 1683, 1514, 1336, 1052, 815, 743, 721 cm -1 ; 1 H NMR (400 MHz, DMSO-d 6 ): δ 9.93 (s, 1H, OH), 8.04 (d, J = 8.6 Hz, 1H, NH), (m, 3H, ArH), 7.58 (d, J = 8.5 Hz, 1H, ArH), 7.49 (d, J = 1.5 Hz, 1H, ArH), 7.44 (t, J = 7.5 Hz, 1H, ArH), 7.38 (dd, J = 6.8, 1.8 Hz, 1H, ArH), 7.28 (t, J = 7.4 Hz, 1H, ArH), 7.14 (d, J = 8.8 Hz, 1H, ArH), 6.86 (d, J = 8.1 Hz, 1H, CH), 3.98 (q, J = 6.7 Hz, 2H, CH 2 ), 1.14 (t, J = 6.4 Hz, 3H, CH 3 ); 13 C NMR (100 MHz, DMSO-d 6 ): δ 156.2, 154.0, 139.3, 133.5, 132.9, 132.3, 131.7, 130.1, 129.1, 129.0, 128.7, 127.0, 126.9, 123.1, 122.8, 119.0, 116.8, 60.4, 49.7, 15.0; MS (ESI): m/z 389 [(M-H) -, 100]; Anal. Calcd for C 20 H 17 NO 3 Cl 2 : C, 61.55; H, 4.39; N, Found: C, 61.42; H, 4.27; N, 3.66%. Benzyl ((2-nitrophenyl)(2-hydroxynaphthalen-1- yl)methyl) carbamate, 4s: White solid; IR (KBr): 3424, 3250, 1702, 1528, 1334, 1046, 834, 752, 696 cm -1 ; 1 H NMR (400 MHz, DMSO-d 6 ): δ 9.81 (s, 1H, OH), 8.08 (d, J = 7.9 Hz, 1H, NH), 7.94 (d, J = 8.2 Hz, 1H, ArH), 7.79 (d, J = 8.0 Hz, 1H, ArH), 7.74 (t, J = 7.3 Hz, 2H, ArH), (m, 11H, ArH), 7.08 (d, J = 8.5 Hz, 1H, CH), 5.12 (d, J = 12.8 Hz, 1H, CH 2 ), 5.06 (d, J = 12.8 Hz, 1H, CH 2 ); 13 C NMR (100 MHz, DMSO-d 6 ): δ 156.3, 154.1, 149.0, 137.5, 136.9, 133.3, 132.6, 130.4, 129.7, 129.4, 128.9, 128.7, 128.5, 128.2, 128.1, 127.8, 127.2, 127.0, 124.5, 123.0, 122.9, 118.8, 116.4, 65.9, 48.3; MS (ESI): m/z 427 [(M-H) -, 100]; Anal. Calcd for C 25 H 20 N 2 O 5 : C, 70.09; H, 4.71; N, Found: C, 69.94; H, 4.75; N, 6.63%. Benzyl ((4-nitrophenyl)(2-hydroxynaphthalen-1- yl)methyl) carbamate, 4u: White solid; IR (KBr): 3414, 3065, 1686, 1515, 1347, 1050, 824, 745, 695 cm -1 ; 1 H NMR (400 MHz, DMSO-d 6 ): δ (s, 1H, OH), 8.15 (d, J = 8.7 Hz, 2H, ArH), 7.99 (d, J = 6.6 Hz, 1H, NH), 7.93 (d, J = 6.4 Hz, 1H, ArH), 7.82 (t, J = 8.7 Hz, 2H, ArH), 7.50 (d, J = 8.5 Hz, 2H, ArH), (m, 7H, ArH), 7.24 (d, J = 8.8 Hz, 1H, ArH), 7.01 (d, J = 7.8 Hz, 1H, CH), 5.14 (d, J = 12.6 Hz, 1H, CH 2 ), 5.08 (d, J = 12.6 Hz, 1H, CH 2 ); 13 C NMR (100 MHz, DMSO-d 6 ): δ 156.6, 153.6, 151.1, 146.5, 137.3, 132.3, 130.3, 129.1, 128.8, 128.7, 128.2, 127.5, 127.2, 123.7, 123.3, 123.0, 118.8, 118.3, 66.3, 50.6; MS (ESI): m/z 427 [(M-H) -, 100]; Anal. calcd. for C 25 H 20 N 2 O 5 : C, 70.09; H, 4.71; N, Found: C, 70.20; H, 4.64; N, 6.43%. Benzyl ((2-chlorophenyl)(2-hydroxynaphthalen- 1-yl)methyl) carbamate, 4v: White solid; IR (KBr): 3421, 3170, 1700, 1518, 1336, 1050, 819, 753, 694 cm -1 ; 1 H NMR (400 MHz, DMSO-d 6 ): δ 9.96 (s, 1H, OH), 8.04 (d, J = 7.8 Hz, 2H, ArH), (m, 2H, NH and ArH), (m, 10H, ArH), 7.16 (d, J = 7.3 Hz, 2H, ArH), 6.94 (d, J = 5.8 Hz, 1H, CH), 5.09 (d, J = 12.0 Hz, 1H, CH 2 ), 5.01 (d, J = 12.0 Hz, 1H, CH 2 ); 13 C NMR (100 MHz, DMSO-d 6 ): δ 156.0, 153.9, 139.7, 137.6, 133.0, 132.9, 130.3, 129.9, 129.7, 129.0, 128.9, 128.7, 128.1, 127.9, 127.0, 126.8, 123.4, 122.8, 119.0, 117.3, 65.8, 50.1; MS (ESI): m/z 416 [(M-H) -, 100]; Anal. Calcd for C 25 H 20 NO 3 Cl: C, 71.86; H, 4.82; N, Found: C, 71.98; H, 4.76; N, 3.28%. Benzyl ((4-chlorophenyl)(2-hydroxynaphthalen- 1-yl)methyl) carbamate, 4w: White solid; IR (KBr): 3402, 3200, 1681, 1515, 1321, 1042, 812, 746, 696 cm -1 ; 1 H NMR (400 MHz, DMSO-d 6 ): δ (s, 1H, OH), 7.93 (d, J = 8.2 Hz, 1H, NH), (m, 3H, ArH), (m, 12H, ArH), 6.90 (d, J = 8.1 Hz, 1H, CH), 5.11 (d, J = 12.6 Hz, 1H, CH 2 ), 5.01 (d, J = 12.6 Hz, 1H, CH 2 ); 13 C NMR (100 MHz, DMSO-d 6 ): δ 156.5, 153.4, 141.8, 137.3, 132.4, 131.4, 130.0, 129.0, 128.8, 128.7, 128.4, 128.3, 128.2, 127.4, 127.0, 123.7, 123.5, 122.8, 118.9, 118.7, 66.2, 50.3; MS (ESI): m/z 416 [(M-H) -, 100]; Anal. Calcd for C 25 H 20 NO 3 Cl: C, 71.86; H, 4.82; N, Found: C, 71.99; H, 4.73; N, 3.40%. Benzyl ((2,4-dichlorophenyl)(2-hydroxy-naphthalen- 1-yl)methyl) carbamate, 4x: White solid; IR (KBr): 3416, 3066, 1686, 1522, 1341, 1054, 819, 744, 719 cm -1 ; 1 H NMR (400 MHz, DMSO-d 6 ): δ 9.92 (s, 1H, OH), (m, 2H, NH and ArH), 7.80 (d, J = 8.0 Hz, 1H, ArH), 7.75 (d, J = 8.8 Hz, 1H, ArH), 7.56 (d, J = 8.4 Hz, 1H, ArH), (m, 9H, ArH), 7.14 (d, J = 8.7 Hz, 1H, ArH), 6.87 (d, J = 6.7 Hz, 1H, CH), 5.09 (d, J = 12.8 Hz, 1H, CH 2 ), 5.01 (d, J = 12.8 Hz, 1H, CH 2 ); 13 C NMR (100 MHz, DMSO-d 6 ): δ 156.1, 154.0, 139.2, 137.5, 133.6, 133.0, 132.3, 131.7, 130.2, 129.1, 129.0, 128.7, 128.6, 128.1, 127.9, 127.0, 126.9, 123.1, 122.8, 118.9, 116.6, 65.9, 49.9; MS (ESI): m/z 451 [(M-H) -, 100]; Anal. Calcd for C 25 H 19 NO 3 Cl 2 : C, 66.38; H, 4.23; N, Found: C, 66.51; H, 4.14; N, 3.03%. Conclusion In conclusion, a very simple and efficient method for the synthesis of 1-carbamatoalkyl-2-naphthols has been developed. The catalyst showed good efficiency

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