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Synlett 2006(20): 3464-3468  
DOI: 10.1055/s-2006-956490
LETTER
© Georg Thieme Verlag Stuttgart · New York

Chemistry of Polyhalogenated Nitrobutadienes, 3: [4+2] Cycloadditions of (Z)-1,1,4-Trichloro-2,4-dinitrobuta-1,3-diene and Subsequent Reactions

Viktor A. Zapol’skiia, Jan C. Namysloa, Björn Blaschkowskib, Dieter E. Kaufmann*a
a Institut für Organische Chemie, Technische Universität Clausthal, 38678 Clausthal-Zellerfeld, Germany
Fax: +49(5323)722834; e-Mail: dieter.kaufmann@tu-clausthal.de;
b Institut für Anorganische und Analytische Chemie, Technische Universität Clausthal, 38678 Clausthal-Zellerfeld, Germany
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Publication History

Received 18 August 2006
Publication Date:
08 December 2006 (online)

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Abstract

The multifaceted chemical behavior of polyhalogenated nitrobutadienes, such as 1 and 2, inspired us to test their features in [4+2] cycloaddition reactions. It appears that in the presence of an appropriate diene only the β-chloro-β-nitro vinyl moiety of 1 acts as an efficient dienophile. The resulting cycloaddition products were subsequently converted at the β,β-dichloro position by means of a suitable N,O- and N,N-bisnucleophile to give benzoxazole or benzimidazole derivatives. The latter reaction products proved valuable for crop protection.

Key words

nitro compound - haloalkene - cycloaddition - Diels-Alder - heterocycle

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The herbicidal 2,4-dichloro-1-(4-nitrophenoxy)benzene is reasonably anticipated to be a human carcinogen, see: The Merck Index, 13th ed., 2001 (CD-ROM).

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Crystal Data for 9.
C15H12ClN3O5, M = 349.73 g mol-1, crystal size 0.2 × 0.2 × 0.5 mm were collected on a Stoe IPDS II diffractometer using λ = 0.71073 Å [T = 223(2) K]. The crystal structure was solved by direct methods and refined by full matrix least squares on F2 (SHELX-97) in the space group P21/n (monoclinic), lattice parameters a = 7.2336(12) Å, b = 19.414(3) Å, α = 10.834(2) Å, β = 96.523(15)°, V = 1511.7(4) Å3, Z = 4, d calc. = 1.537 g cm-3, F(000) = 720, absorption coefficient = 0.286 mm-1 using 2682 indepen-dent reflections and 265 parameters. R1 = 0.0489, wR2 = 0.0995 [I > 2s(I)], goodness of fit on F 2 = 0.971, residual electron density = 0.203 and -0.267 e Å-3. CCDC 278475 contains supplementary crystallographic data for this paper, obtainable free of charge from www.ccdc.cam.ac.uk or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 (1223)336033; or deposit@ccdc.cam.ac.uk.

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Experimental Details.
Melting points were measured on a Büchi 520 apparatus and were uncorrected. 1H NMR, 13C NMR, 14N NMR, and 15N NMR spectra were obtained on a Bruker Avance with 400 MHz proton frequency, 15N NMR were measured in inverse 2D mode (gs-HMBC). 1H NMR spectra in CDCl3 were referenced to tetramethylsilane (TMS) at δ = 0.0 ppm; 13C NMR spectra refer to the solvent signal center at δ = 77.0 ppm. Other solvents as follows: DMSO-d 6: 2.50 ppm (1H), 39.70 ppm (13C); (CD3)2CO: 2.04 ppm (1H), 29.8 ppm (13C), C6D6: 7.20 ppm (1H), 128.0 ppm (13C). N NMR spectra were externally referenced to nitromethane at δ = 0.0 ppm. IR spectra were obtained on a Bruker ‘Vector 22’ FT IR as KBr IR. Mass spectra were recorded on a Hewlett Packard system ‘MS 5989B’ with direct inlet. All masses of chlorine containing molecules or fragments refer to the isotope 35Cl. High-resolution mass spectra were measured with a Varian MAT 311 A spectrometer with pre-selected molecular ion peak matching at R >> 10000 to be within ± 2 ppm of the exact masses. Elemental analyses were performed by Institut für Pharmazeutische Chemie, TU Braunschweig. TLC was carried out on Merck plates coated with silica gel (60 F 254). Silica gel 60 was also used for column chromatography.
( Z )-1,1,4-Trichloro-2,4-dinitro-1,3-butadiene ( 1). [3]
Yellow solid, mp 70-71 °C. 1H NMR (CDCl3): δ = 8.12 (s, 1 H). 13C NMR (CDCl3): δ = 142.6 (C-4), 141.5 (C-2), 135.7 (C-1), 118.1 (C-3). 15N NMR (CDCl3): δ = -20.5, -21.4.
4-Chloro-5-(2,2-dichloro-1-nitrovinyl)-1-methyl-4-nitrocyclohex-1-ene ( 7a) and 5-Chloro-4-(2,2-dichloro-1-nitrovinyl)-2-methyl-5-nitrocyclohex-1-ene ( 6b). An ampule was charged with 0.50 g (2.00 mmol) dinitrodiene 1, 0.68 g (10.0 mmol) isoprene (3), and 10 mg (0.1 mmol) hydroquinone and sealed. The mixture was stirred under N2 atmosphere for 60 h at 80-85 °C. After extraction thrice with PE-Et2O (3:1) and separation of poly-meric by-product, the solvent and residual volatiles were evaporated in vacuo. The crude product was purified by column chromatography with PE as the eluent. Yield 0.16 g (25%) of 6a,b, mp 118-119 °C. Isomeric ratio 6a/6b = 3:1. IR (KBr): 2937, 2915, 1618 (C=C), 1566 (NO2), 1543 (NO2), 1442, 1430, 1364 (NO2), 1350 (NO2), 1054, 1021, 978, 935, 843, 774, 706, 643, 588 cm-1. 1H NMR (CDCl3): δ (major isomer) = 1.73 (s, 3 H, CH3), 2.52 (m, 1 H, CH2), 2.70 (m, 1 H, CH2), 2.92 (m, 1 H, CH2), 3.27 (m, 1 H, CH2), 4.48 (dd, ³ J = 8.5, 6.0 Hz, 1 H, H-5), 5.31 (m, 1 H, -CH=); δ (minor isomer) = 1.72 (s, 3 H, CH3), 2.42 (m, 1 H, CH2), 2.65 (m, 1 H, CH2), 2.85 (m, 1 H, CH2), 3.35 (m, 1 H, CH2), 4.39 (dd, 3 J = 8.3, 5.8 Hz, 1 H, H-4), 5.43 (m, 1 H, -CH=). 13C NMR (CDCl3): δ (major isomer) = 22.59 (CH3), 32.58 (CH2), 40.73 (CH2), 44.26 (-CH-), 102.42 [C(NO2)Cl], 115.84 (CH=), 127.84 (=CCl2), 132.54 (=C-Me), 146.73 [=C(NO2)]; δ (minor isomer) = 22.47 (CH3), 27.98 (CH2), 43.88 (CH), 44.80 (CH2), 102.67 [C(NO2)Cl], 118.45 (CH=), 127.81 (=CCl2), 129.74 (=C-Me), 146.77 [=C(NO2)]. MS (GC-MS, EI): m/z (%) = 314 (3) [M+], 297 (2), 267 (7), 250 (14), 221 (17), 185 (45), 149 (60), 125 (35), 115 (100). Anal. Calcd for C9H9Cl3N2O4 (315.54): C, 34.26; H, 2.87; N, 8.88. Found: C, 34.49; H, 2.91; N, 8.49.
4-Chloro-5-(2,2-dichloro-1-nitrovinyl)-1,2-dimethyl-4-nitrocyclohex-1-ene ( 7).
Preparation as described for 6a,b, except for reaction conditions: 65-70 °C, 40 h. Yield 37%, mp 84-85 °C. IR (KBr): 2922, 1619 (C=C), 1562 (NO2), 1541 (NO2), 1433, 1368 (NO2), 1352 (NO2), 1252, 1061, 953, 852, 810, 778, 637 cm-1. 1H NMR (CDCl3): δ = 1.65 (br s, 6 H, 2 CH3), 2.46 (dd, 2 J = 17.8 Hz, 3 J = 5.8 Hz, 1 H, H-6), 2.64 (dd, 2 J = 17.8 Hz, 3 J = 8.1 Hz, 1 H, H-6), 2.80 (d, 2 J = 17.6 Hz, 1 H, H-3), 3.27 (d, 2 J = 17.6 Hz, 1 H, H-3), 4.44 (dd, 3 J = 8.1, 5.8 Hz, 1 H, H-5). 13C NMR (CDCl3): δ = 18.2 (CH3), 18.3 (CH3), 33.6 (C-6), 44.3 (C-5), 45.6 (C-3), 102.6 (C-4), 121.7 (=C-Me), 124.0 (=C-Me), 127.7 (=CCl2), 146.8 [=C(NO2)]. MS (direct inlet): m/z (%) = 328 (2) [M+], 313 (1), 298 (2), 281 (9), 264 (8), 246 (6), 235 (27), 199 (33), 164 (34), 139 (19), 129 (41), 105 (36), 43 (100). Anal. Calcd for C10H11Cl3N2O4 (329.57): C, 36.44; H, 3.36; N, 8.50. Found: C, 36.60; H, 3.33; N, 8.22.
2- exo -Chloro-3- exo -(2,2-dichloro-1-nitrovinyl)-2- endo -nitrobicyclo[2.2.1]hept-5-ene ( 8).
Procedure: 0.50 g (2.0 mmol) dinitrodiene 1 and 1.32 g (20 mmol) cyclopentadiene (5) were stirred for 4 d at r.t. Subsequently, the mixture was cooled down to 0 °C. The precipitated crude product was filtered off and recrystallized from PE-Et2O (1:1). Yield 0.38 g (60%), mp 119-120 °C. IR (KBr): 3082, 3013, 2975, 2888, 1608, 1575 (NO2), 1535 (NO2), 1458, 1360 (NO2), 1338 (NO2), 1254, 1172, 1065, 987, 971, 950, 888, 808, 767, 703, 676, 645, 591, 544 cm-1. 1H NMR (CDCl3): δ = 1.93 (s, 2 H, CH2), 3.38 (s, 1 H, H-4), 3.60 (s, 1 H, H-1), 4.31 (s, 1 H, H-3), 6.07 (br s, 1 H, H-6), 6.56 (br s, 1 H, H-5). 1H NMR (C6D6): δ = 1.25 (d, 2 J = 10.7 Hz, 1 H, H-7 syn ,), 1.70 (d, 2 J = 10.7 Hz, 1 H, H-7 anti ), 2.79 (m, 1 H, H-4), 3.10 (br s, 1 H, H-1), 3.98 (d, 3 J = 2.1 Hz, 1 H, H-3), 5.50 (dd, 3 J = 5.5, 3.2 Hz, 1 H, H-6), 5.71 (dd, 3 J = 5.5, 3.2 Hz, 1 H, H-5). 13C NMR (CDCl3): δ = 46.6 (C-3), 47.2 (CH2), 50.8 (C-4), 56.6 (C-1), 108.4 (C-2), 128.8 (=CCl2), 134.5 (C-6), 141.3 (C-5), 148.1 [=C(NO2)]. MS (GC-MS): m/z (%) = 266 (2) [M - NO2 +], 219 (13), 183 (38), 149 (73), 136 (21), 115 (34), 66 (100). HRMS (EI) [M+]: m/z calcd for C9H7Cl3N2O4: 311.9471.
2- exo -{(3- exo -Chloro-3-nitrobicyclo[2.2.1]hept-5-en-2-yl)nitromethyl}benzoxazole ( 9). To a suspension of 0.40 g (1.28 mmol) bicycloheptene 8 in 10 mL MeOH was added a solution of 0.46 g (4.23 mmol) o-aminophenol in 20 mL MeOH at 0 °C within 10 min. The mixture was kept at 0-10 °C for 1 h, then 4 h at r.t. After addition of 10 drops of concd HCl and 1 h at r.t., the mixture was cooled down to 0 °C. The precipitate was sucked off, washed thrice with H2O and once with 10 mL of cold MeOH. Drying in vacuo yielded 0.38 g (85%) of benzoxazole 9, mp 165-167 °C. IR (KBr): 3018, 1611, 1568 (NO2), 1557 (NO2), 1481, 1451, 1353 (NO2), 1232, 1173, 1067, 1003, 977, 950, 912, 879, 805, 784, 760, 749, 732, 687, 574, 513 cm-1. 1H NMR (CD3COCD3): δ = 1.92 (ddd, J = 10.3, 4.2, 2.1 Hz, 1 H, H-7 syn ), 2.43 (d, 1 H, H-7 anti , 2 J = 10.3 Hz), 2.88 (m, 1 H, H-1), 3.70 (m, 1 H, H-4), 4.35 (dd, J = 11.5, 2.1 Hz, 1 H, H-2), 6.09 (dd, J = 5.6, 3.1 Hz, 1 H, H-5), 6.48 [d, J = 11.5 Hz, 1 H, -CH(NO2)], 6.66 (dd, J = 5.6, 3.1 Hz, 1 H, H-6), 7.50 (ddd, J = 7.8, 7.5, 1.2 Hz, 1 H, Haryl,), 7.56 (ddd, J = 8.1, 7.5, 1.4 Hz, 1 H, Haryl), 7.78 (ddd, J = 8.1, 1.2, 0.7 Hz, 1 H, Haryl), 7.86 (ddd, J = 7.8, 1.4, 0.7 Hz, 1 H, Haryl). 13C NMR (CD3COCD3): δ = 46.9 (C-1), 47.6 (C-7), 50.4 (C-2), 60.1 (C-4), 85.8 [-CH(NO2)], 109.7 (C-3), 112.2 (Caryl), 121.8 (Caryl), 126.4 (Caryl), 128.0 (Caryl), 133.4 (C-5), 141.2 (Cquat.,aryl), 142.9 (C-6), 151.7 (Cquat.,aryl), 158.2 (C=N). MS: m/z (%) = 304 (2) [M - NO2 +], 273 (32), 256 (10), 238 (100), 220 (58), 204 (47), 191 (50). HRMS (EI) [M+]: m/z calcd for C15H12ClN3O5: 349.0465. [15]
2- exo -{(3- exo -Chloro-3-nitrobicyclo[2.2.1]hept-5-en-2-yl)nitromethyl}-1 H -benzimidazole ( 10).
Prepared in analogy to compound 9 from bicycloheptene 8 and o-phenylenediamine (ratio 1:2.2), yield 80%, mp 105-107 °C. IR (KBr): 3385, 2998, 1621 (C=C), 1561 (NO2), 1456, 1430, 1346 (NO2), 1231, 1149, 1061, 958, 906, 840, 784, 749, 616, 578, 439 cm-1. 1H NMR (CD3COCD3): δ = 1.85 (dd, J = 10.2, 2.1 Hz, 1 H, H-7 syn ), 2.34 (d, 2 J = 10.2 Hz, 1 H, H-7 anti ), 2.64 (m, 1 H, H-1), 3.66 (m, 1 H, H-4), 4.49 (m, 1 H, H-2), 6.06 (dd, J = 5.6, 3.0 Hz, 1 H, H-5), 6.39 [d, J = 11.6 Hz, 1 H, -CH(NO2)], 6.62 (dd, J = 5.6, 3.0 Hz, 1 H, H-6), 7.36 (m, 2 H, Haryl), 7.72 (m, 2 H, Haryl). 13C NMR (CD3COCD3): δ = 47.0 (C-1), 47.7 (CH2), 50.6 (C-2), 60.1 (C-4), 86.0 [-CH(NO2)], 110.1 (C-3), 116.8 (2 C, Caryl), 124.8 (2 C, Caryl), 133.2 (C-5), 138.4 (2 C, Cquat.,aryl), 143.0 (C-6), 146.1 (C=N). MS: m/z (%) = 348 (2) [M+], 302 (34), 287 (12), 272 (35), 255 (15), 237 (100), 219 (92). HRMS (EI) [M+]: m/z calcd for C15H13ClN4O4: 348.0625.