Synthesis of benzofuran derivatives via different methods

Synthetic Communications

Volumn 44, Issue 16, 2014, Pages 2285-2312

  Abu Hashem, Ameen A ^a,b   Hussein, Hoda A R ^a   Aly, Ahmed S ^a   Gouda, Moustafa A ^c,d  

^a NATIONAL RESEARCH CENTRE   (Egypt)

^b JAZAN UNIVERSITY   (Saudi Arabia)

^c Mansoura University   (Egypt)

^d TAIBAH UNIVERSITY   (Saudi Arabia)

Author keywords

Benzofurans; fused heterocycles; synthesis

Indexed keywords

BENZOFURAN DERIVATIVE; KHELLIN; KHELLINONE; UNCLASSIFIED DRUG; VISNAGIN; VISNAGINONE;

ALKYLATION; CYCLIZATION; DRUG STRUCTURE; HYDROLYSIS; OLEFINATION; ONE POT SYNTHESIS; REVIEW; SUBSTITUTION REACTION;

EID: 84904071201     PISSN: 00397911     EISSN: 15322432     Source Type: Journal    
DOI: 10.1080/00397911.2014.894528     Document Type: Review

References (84)

1. Lau, C. K.; Belanger, P. C.; Dufresne, C.; Scheigetz, J.; Therien, M.; Fitzsimmons, B.; Young, R. N.; Ford-Hutchison, A. W.; Riendeau, D.; Denis, D.; Guay, J.; Charleson, S.; Piechuta, H.; McFarlane, C. S.; Lee Chiu, S. H.; Eline, D.; Alvaro, R. F.; Miwa, G.; Walsh, J. L. Development of 2,3-dihydro-6-(3- phenoxypropyl)-2-(2-phenylethyl)-5-benzofuranol (L-670, 630) as a potent and orally active inhibitor of 5-lipoxygenase. J. Med. Chem. 1992, 35, 1299-1318.
2. Echneiders, G. E.; Stevenson, R. Synthesis of (±)-machicendiol. J. Org. Chem. 1979, 44, 4710.
3. Stille, J. R.; Ward, J. A.; Leffelman, C.; Sullivan, K. A. 5-Formyl salicylaldehyde as a linker for the synthesis of benzofuran-containing insulin sensitivity enhancer compounds. Tetrahedron Lett. 1996, 37, 9267-9270.
4. Black, D. St. C.; Rezaie, R. Modified Vilsmeier reactions of activated benzofurans with indolines: Synthesis of benzofuran-fused benzocarbazoles. Tetrahedron Lett. 1999, 40, 4251-4254.
5. Kao, C. L.; Chern, J. W. A convenient synthesis of naturally occurring benzofuran ailanthoidol. Tetrahedron Lett. 2001, 42, 1111-1113.
6. Fuganti, C.; Serra, S. A new approach to 2-aryl-7-alkoxy-benzofurans: Synthesis of ailanthoidol, a natural neolignan. Tetrahedron Lett. 1998, 39, 5609-5610.
7. Basawaraj, R.; Yadav, B.; Sangapure, S. S. Synthesis of some 1H pyrazolines bearing benzofuran as biologically active agents. Indian J. Heterocycl. Chem. 2001, 11, 31-34.
8. Rida, S. M.; El-Hawash, S. A. M.; Fahmy, H. T. Y.; Hazzaa, A. A.; El-Meligy, M. M. M. Synthesis of novel benzofuran and related benzimidazole derivatives for evaluation of in vitro anti-HIV-1, anticancer and antimicrobial activities. Arch. Pharm. Res. 2006, 29, 826-833.
9. Ujjinamatada, R. K.; Appala, R. S.; Agasimundin, Y. S. Synthesis and antimicrobial activity of new benzofuranyl-1,3-benzoxazines and 1,3-benzoxazin-2-ones. J. Heterocycl. Chem. 2006, 43, 437-441.
10. Wachi, S.; Takagi, K.; Menichi, G.; Hubert-Habart, M. Research on potential antitumor agents: Methods for preparing hydropyrimidines from coumarins. Bull. Soc. Chem. 1978, 56, 230-233.
11. Singh, D. V.; Mishra, A. R.; Mishra, R. M.; Pandey, A. K.; Singh, C. R.; Dwivedi, A. K. Synthesis and fungicidal activity of benzofuran-incorporated substituted pyrimidines. Indian J. Heterocycl. Chem. 2005, 14, 319-322.
12. Abdel-Wahab, B. F.; Abdel-Aziz, H.A.; Ahmed, E. M. Synthesis and antimicrobial evaluation of 1-(benzofuran-2-yl)-4-nitro-3-arylbutan-1-ones and 3-(benzofuran-2-yl)-4,5-dihydro-5-aryl-1-[4-(aryl)-1,3-thiazol-2-yl] -1H-pyrazoles. Eur. J. Med. Chem. 2009, 44, 2632-2635.
13. Chundawat, T. S.; Sharma, N.; Bhagat, S. Synthesis and in vitro antimicrobial evaluation of novel fluorine-containing 3-benzofuran-2-yl-5- phenyl-4,5-dihydro-1H-pyrazoles and 3-benzofuran-2-yl-5-phenyl-4,5- dihydroisoxazoles. Med. Chem. Res. In press. DOI: 10.1007/s00044-013-0735-9.
14. Dawood, K. M.; Abdel-Gawad, H.; Rageb, E. A.; Ellithey, M.; Mohamed, H. A. Synthesis, anticonvulsant, and anti-inflammatory evaluation of some new benzotriazole and benzofuran-based heterocycles. Bioorg. Med. Chem. 2006, 14, 3672-3680.
15. Sauzem, P. D.; Machado, P.; Rubin, M. A.; Sant'Anna, G. S.; Faber, H. B.; Souza, A. H.; Mello, C. F.; Beck, P.; Burrow, R. A.; Bonacorso, H. G.; Zanatta, N.; Martins, M. A. P. Design and microwave-assisted synthesis of 5-trifluoro methyl-4,5-dihydro-1H-pyrazoles: Novel agents with analgesic and anti-inflammatory properties. Eur. J. Med. Chem. 2008, 43, 1237-1247.
16. 1 receptor antagonists within vivo analgesic efficacy. Bioorg. Med. Chem. Lett. 2008, 18, 3392-3399.
17. Souza, F. R.; Souza, V. T.; Ratzlaff, V.; Borges, L. P.; Oliveira, M. R.; Bonacorso, H. G.; Zanatta, N.; Martins, M. A. P.; Mello, C. F. Hypothermic and antipyretic effects of 3-methyl- and 3-phenyl-5-hydroxy-5-trichloromethyl-4,5- dihydro-1H-pyrazole-1-carboxyamides in mice. Eur. J. Pharm. 2002, 451, 141-147.
18. Kamal, M.; Shakya, A. K.; Jawaid, T. Benzofurans: A new profile of biological activities. Int. J. Med. Pharm. Sci. 2011, 1(3), 1-15.
19. Manna, F.; Chimenti, F.; Bolasco, A.; Secci, D.; Bizzarri, B.; Befani, O.; Turini, P.; Mondovì, B.; Alcaro, S.; Tafi, A. Inhibition of amine oxidases activity by 1-acetyl-3,5-diphenyl-4,5-dihydro-(1H)-pyrazole derivatives. Bioorg. Med. Chem. Lett. 2002, 12, 3629-3633.
20. Abid, M.; Azam, A. Synthesis and antiamoebic activities of 1-N-substituted cyclised pyrazoline analogues of thiosemicarbazones. Bioorg. Med. Chem. 2005, 13, 2213-2220.
21. Turan-Zitouni, G.; Chevallet, P.; Kiliç, F. S.; Erol, K. Synthesis of some thiazolylpyrazoline derivatives and preliminary investigation of their hypotensive activity. Eur. J. Med. Chem. 2000, 35, 635-641.
22. Kumar, V.; Aggarwal, R.; Tyagi, P.; Singh, S. P. Synthesis and antibacterial activity of some new 1-heteroaryl-5-amino-4-phenyl-3- trifluoromethyl pyrazoles. Eur. J. Med. Chem. 2005, 40, 927.
23. Gans, K. R.; Galbraith, W.; Roman, R. J.; Haber, S.B.; Kerr, J. S.; Schmidt, W.K.; Smith, C.; Hewes, W. C.; Ackerman, N. R. Anti-inflammatory and safety profile of DuP 697, a novel orally effective prostaglandin synthesis inhibitor. J. Pharm. Exp. Ther. 1990, 254, 180-187.
24. Nosova, E. V.; Kravchenko, M. A.; Lipunova, G. N.; Chasovskikh, O. M.; Sokolov, V. A.; Charushin, V.N. Synthesis and antituberculous activity of fluorinated 3-R-hydrazino-2-benzoylacrylates and their cyclization products. Pharm. Chem. J. 2002, 36, 585-587.
25. Tzu-Wei, T.; Eng-Chi, W.; Sie-Rong, L. Y. C.; Yu-Li, L.; You-Feng, W.; Keng-Shiang, H. A new synthesis of benzofurans from phenols via Claisen rearrangement and ring-closing metathesis. J. Chin. Chem. Soc. 2004, 51, 1307-1318.
26. Keng-Shiang, H.; Sie-Rong, L.; You-Feng, W.; Yu-Li, L.; Yung-Hua, C.; Tzu-Wei, T.; Chih-Hui, Y.; Eng-Chi, W. Synthesis of certain benzo-heterocyclic compounds from 2-hydroxy acetophenone via cyclization and ring-closing metathesis. J. Chin. Chem. Soc. 2005, 52, 159-167.
27. Fu-lin, Y.; Ai-xia, W.; Zhong-jian, J. Benzofuran derivatives from Ligularia stenocephala. J. Chin. Chem. Soc. 2004, 51, 863-868.
28. Huang, K. S.; Wang, E. C. A novel synthesis of substituted naphthalenes via Claisen rearrangement and RCM reaction. Tetrahedron Lett. 2001, 42, 6155-6157.
29. Wang, E. C.; Hsu, M. K.; Lin, Y. L.; Huang, K. S. A new synthesis of substituted 2,5-dihydrobenzo[b]oxepines. Heterocycles 2002, 57, 1997.
30. Wang, E. C.; Wang, C. C.; Hsu, M. K.; Huang, K. S. A synthesis of substituted 3,6-dihydro-1H-benzo[c]oxocines via Claisen rearrangement and ring-closing metathesis. Heterocycles 2002, 57, 2021.
31. Chi-Lin, C.; Chein-Hwa, H.; Huey-Min, W.; Rei-Sheu, H.; Ling-Ching, C. Hypervalent iodine(III) reagent-mediated synthesis of 2-methyl benzofuran derivatives by Pummerertype reaction in ionic liquid. J. Chin. Chem. Soc. 2011, 58, 90-93.
32. Yin Jun, Z. Y. W. An efficient solid-phase synthesis of substituted benzofuran using selenium-bound resin. Appl. Organomet. Chem. 2012, 26, 212-216.
33. Burgstahler, A. W.; Worden, L. R.; Noland, W. E.; Parham, W. E.; Carol, W. Org. Synth. Coll. 1973, 5, 251; 1966, 46, 28.
34. Suryakant, B.; Sapkal, K. F.; Shelke, B. B. S.; Murlidhar, S. S. An efficient synthesis of benzofuran derivatives under conventional/nonconventional method. Chin. Chem. Lett. 2010, 21, 1439-1442.
35. Rangaswamy, J.; Kumar, H. V.; Harini, S. T.; Naik, N. Synthesis of benzofuran-based 1,3,5-substituted pyrazole derivatives as a new class of potent antioxidants and antimicrobials: A novel accost to amend biocompatibility. Bioorg. Med. Chem. Lett. 2012, 22, 4773-4777.
36. Shang, Y.; Wang, C.; He, X.; Ju, K.; Zhang, M.; Yu, S.; Wu, J. DMAP-catalyzed cascade reaction: One-pot synthesis of benzofurans in water. Tetrahedron 2010, 66, 9629-9633.
37. Liu, J.; Faqin, J.; Jiang, X.; Zhang, W.; Liu, J.; Liu, W.; Fu, L. Synthesis and antimicrobial evaluation of 3-methanone-6-substitutedbenzofuran derivatives. Eur. J. Med. Chem. 2012, 54, 879-886.
38. Telvekar, V. N.; Belubbi, A.; Bairwa, V. K.; Satardekar, K. Novel benzylidene benzofuran-3-carbohydrazide derivatives as antitubercular and antifungal agents. Bioorg. Med. Chem. Lett. 2012, 22, 2343-2346.
39. Yang, L.; Lei, H.; Cheng-Gen, M.; Liu, H.; Zhou, T.; Ying-Lan, Z.; Xiao-Yun, L.; Zi-Cheng, L.; Song, H.; Wen-Cai, H. Synthesis, antiproliferative activities and in vitro biological evaluation of novel benzofuran sulfonamide derivatives. Bioorg. Med. Chem. Lett. 2011, 21, 5389-5392.
40. Ortega, N.; Beiring, B.; Urban, S.; Glorius, F. Highly asymmetric synthesis of (+)-corsifuran A: Elucidation of the electronic requirements in the rutheniume NHC-catalyzed hydrogenation of benzofurans. Tetrahedron 2012, 68, 5185-5192.
41. von Reuß, S. H.; König, W. A. Corsifurans A-C, 2-arylbenzofurans of presumed stilbenold origin from Corsinia coriandrina (Hepaticae). Phytochemistry 2004, 65, 3113-3118.
42. Gates, B. D.; Dalidowicz, P.; Tebben, A.; Wang, S.; Sweton, J. S. Mechanistic aspects and synthetic applications of the electrochemical and iodobenzene bistrifluoroacetate oxidative 1,3-cycloadditions of phenols and electron-rich styrene derivatives. J. Org. Chem. 1992, 57, 2135-2143.
43. Geary, L. M.; Hultin, P. G. 2-Substituted benzo[b]furans from (E)-1,2-dichlorovinyl ethers and organoboron reagents: Scope and mechanistic investigations into the one-pot Suzuki coupling/direct arylation. Eur. J. Org. Chem. 2010, 29, 5563-5573.
44. Jiang, X.; Liu, W.; Zhang, W.; Jiang, F.; Gao, Z.; Zhuang, H.; Fu, L. Synthesis and antimicrobial evaluation of new benzofuran derivatives. Eur. J. Med. Chem. 2011, 46, 3526-3530.
45. Abdel-Rahman, H. A.; Keshka, E. M.; El-Telbanib, E. M. Linearly fused furochromones by intramolecular enaminone reactions. Z. Naturforsch. 2002, 57b, 557-562.
46. Slana, G. B. C. A.; de Azevedo, M. S.; Lopes, R. S. C.; Lopes, C. C.; Cardoso, J. N. Total syntheses of oxygenated brazanquinones via regioselective homologous anionic Fries rearrangement of benzylic o-carbamates. Beilstein J. Org. Chem. 2006, 2, 1-4.
47. Abdel-Wahab, B. F.; Abdel-Aziz, H. A.; Ahmed, E. M. Convenient synthesis and antimicrobial activity of new 3-substituted 5-(benzofuran-2-yl)-pyrazole derivatives. Arch. Pharm. Chem. Life Sci. 2008, 341, 734-739.
48. Keshk, E. M.; Abu-Hashem, A. A.; Girges, M. M.; Abdel-Rahman, A. H.; Badria, F. A. Synthesis of benzo[1,2-b:5,4-b]-difuranyl-triazoles, oxadiazoles, -thiazolidinones, -thiadiazoles, and the use of DNA in evaluation of their biological activity. Phosphorus, Sulfur Silicon Relat. Elem. 2004, 179, 1577-1593.
49. Marriott, K. C.; Bartee, R.; Morrison, A. Z.; Stewart, L.; Wesby, J. Expedited synthesis of benzofuran-2-carboxylic acids via microwave-assisted Perkin rearrangement reaction. Tetrahedron Lett. 2012, 53, 3319-3321.
50. 3-induced C-arylation/cyclization in a single pot: A new route to benzofuran fused N-heterocycles of pharmacological interest. Tetrahedron Lett. 2012, 53, 1134-1138.
51. Leflemme, N.; Stoit, A. R.; Borghese, A. Synthesis of novel 2H-spiro [1-benzofuran-3, 40-piperidin]ol scaffolds. Tetrahedron Lett. 2012, 53, 2432-2435.
52. Katrizky, A. R.; Fali, C. N.; Li, J. General synthesis of polysubstituted benzo(b)furans. J. Org. Chem. 1997, 62, 8205-8209.
53. Nizami, S. A.; Gurumurthy, M.; Chattarjee, S. J.; Panda, D. Evaluation of antimicrobial potency of some synthesized thiazolidin-4-one substituted 1,2,4-triazoles. J. Adv. Pharm. Res. 2010, 1, 26-35.
54. Zhou, L.; Shi, Y.; Xiao, Q.; Liu, Y.; Ye, F.; Zhang, Y.; Wang, J.; CuBr-catalyzed coupling of N-tosylhydrazones and terminal alkynes: Synthesis of benzofurans and indoles. Org. Lett. 2011, 13, 968-971.
55. Wang, J. R.; Manabe, K. Hydroxyterphenylphoshine-palladium catalyst for benzo[b]- furan synthesis from 2-chlorophenols: Bifunctional ligand strategy for cross-coupling of chloroarenes. J. Org. Chem. 2010, 75, 5340-5342.
56. Pei, T.; Chen, C.-Y.; DiMichele, L.; Davies, I. W. Controlled synthesis of 2- and 3-substituted benzo[b]furans. Org. Lett. 2010, 12, 4972-4975.
57. Eidamshaus, C.; Burch, J. D. One-pot synthesis of benzofurans via palladium-catalyzed enolate arylation with o-bromophenols. Org. Lett. 2008, 10, 4211-4214.
58. Liang, Y.; Tao, L.-M.; Zhang, Y.-H.; Li, J.-H. Palladium-catalyzed cross-coupling reactions of 1,2-diiodoalkenes with terminal alkynes: Selective synthesis of unsymmetrical buta-1,3-diynes and 2-ethynylbenzofurans. Synthesis 2008, 3988-3994.
59. 2-catalyzed cyclization of proparyl alcohols with anilines, phenols, and amides for synthesis of indoles, benzofurans, and oxazoles through different annulation mechanisms. J. Org. Chem. 2006, 71, 4951-4955.
60. Dudley, M. E.; Morshed, M. M.; Hossain, M. M. A convenient method of synthesizing 3-ethoxycarbonylbenzofurans from salicylaldehydes and ethyl diazoacetate. Synthesis 2006, 1711-1714.
61. Hirano, K.; Satoh, T.; Miura, M. Copper-catalyzed annulative amination of orthoalkynylphenols with hydroxylamines: Synthesis of 3-aminobenzofurans by umpolung amination strategy. Org. Lett. 2011, 13, 2395-2397.
62. Gewald, K.; Jaensch, H. J. 3-Amino-benzo[b]furane. J. Prakt. Chem. 1973, 315, 779-785.
63. Serykh, V. Y.; Rozentsveig, I. B.; Rozentsveig, G.N.; Chernyshev, K. A. Unexpected formation of benzofuran derivatives in the C-amidoalkylation of p-cresol with 4-chloro-N-(2, 2-dichloro-2-phenylthylidene) benzene sulfonamide. Chem. Heterocycl. Compd. 2012, 47(11), 1339-1344.
64. Kim, H. J.; Seo, J. W.; Lee, M. H.; Shin, D. S.; Kim, H. B.; Cho, H.; Lee, B. S.; Chi, D. Y. New synthetic method for benzofurans from 2-(cyanomethyl)phenyl derivatives. Tetrahedron 2012, 68, 3942-3947.
65. Heidari, M. R.; Foroumadi, A.; Noroozi, H.; Samzadeh-Kermani, A.; Azimzadeh, B. S. Study of the anti-inflammatory and analgesic effects of novel rigid benzofuran-3,4-dihydroxy chalcone by formalin, hot-plate and carrageenan tests in mice. Pak. J. Pharm. Sci. 2009, 22(4), 395-401.
66. Van Otterlo, W. A. L.; Morgans, G. L.; Madeley, L. G.; Kuzvidza, S.; Moleele, S. S.; Thornton, N.; De Koning, C. B. An isomerization-ring-closing metathesis strategy for the synthesis of substituted benzofurans. Tetrahedron 2005, 61, 7746-7755.
67. Denmark, S. E.; Smith, R. C.; Chang, W.-T. T.; Muhuhi, J. M. Cross-coupling reactions of aromatic and heteroaromatic silanolates with aromatic and heteroaromatic halides. J. Am. Chem. Soc. 2009, 131, 3104-3118.
68. Contiero, F.; Jones, K. M.; Matts, E. A.; Porzelle, A.; Tomkinson, N. C. O. Direct preparation of benzofurans from o-arylhydroxylamines. Synlett 2009, 3003-3006.
69. Maimone, T. J.; Buchwald, S. L. Pd-catalyzed o-arylation of ethyl acetohydroximate: Synthesis of o-arylhydroxylamines and substituted benzofurans. J. Am. Chem. Soc. 2010, 132, 9990-9991.
70. De Luca, L.; Giacomelli, G.; Nieddu, G. A facile approach to the synthesis of chiral 2-substituted benzofurans. J. Org. Chem. 2007, 72, 3955-3957.
71. Kumar, S.; Namkung, W.; Verkman, A. S.; Sharma, P. K. Novel 5-substituted benzyloxy-2-arylbenzofuran-3-carboxylic acids as calcium activated chloride channel inhibitors. Bioorg. Med. Chem. 2012, 20, 4237-4244.
72. Takeda, N.; Miyata, O.; Naito, T. Efficient synthesis of benzofurans utilizing [3,3]-sigmatropic rearrangement triggered by N-trifluoroacetylation of oxime ethers: short synthesis of natural 2-arylbenzofurans. Eur. J. Org. Chem. 2007, 1491-1509.
73. Carril, M.; San Martin, R.; Tellitu, I.; Dominguez, E. On-water chemistry: Copper-catalyzed straightforward synthesis of benzo[b]furan derivatives in neat water. Org. Lett. 2006, 8, 1467-1470.
74. Chen, C.-Y.; Dormer, P. G. Synthesis of benzo[b]furans via CuI-catalyzed ring closure. J. Org. Chem. 2005, 70, 6964-6967.
75. 4-catalyzed indirect anti-Markovnikov hydration of alkynes: Application to the synthesis of benzo[b]furans. J. Org. Chem. 2007, 72, 6149-6153.
76. Lvarez, R.; Martinez, C.; Madich, Y.; Denis, J. G.; Aurrecoechea, J. M.; de Lera, N. R. A general synthesis of alkenyl-substituted benzofurans, indoles, and isoquinolones by cascade palladium-catalyzed heterocyclization/oxidative Heck coupling. Chem. Eur. J. 2010, 16, 12746-12753.
77. Ghosh, S.; Das, J.; Saikh, F. A new synthesis of 2-aryl/alkyl benzofurans by visible light-stimulated intermolecular Sonogashira coupling and cyclization reaction in water. Tetrahedron Lett. 2012, 53, 5883-5886.
78. Nakamura, I.; Mizushima, Y.; Yamamoto, Y. Synthesis of 2,3-disubstituted benzofurans by platinum-olefin-catalyzed carboalkoxylation of o-alkynylphenyl acetals. J. Am. Chem. Soc. 2005, 127, 15022-15023.
79. Anderson, K. W.; Ikawa, T.; Tundel, R. E.; Buchwald, S. L. The selective reaction of aryl halides with KOH: Synthesis of phenols, aromatic ethers, and benzofurans. J. Am. Chem. Soc. 2006, 128, 10694-10695.
80. Yue, D.; Yao, T.; Larock, R. C. Synthesis of 2,3-disubstituted benzo[b]furans by the palladium-catalyzed coupling of o-iodoanisoles and terminal alkynes, followed by electrophilic cyclization. J. Org. Chem. 2005, 70, 10292-10296.
81. Yang, N.; Wang, Q.; Wang, W.; Wang, J.; Li, F.; Tan, S.; Cheng, M. The design, synthesis, and in vitro immune suppressive evaluation of novel isobenzofuran derivatives. Bioorg. Med. Chem. Lett. 2012, 22, 53-56.
82. Katsura, Y.; Zhang, X.-Y.; Homma, K.; Rice, K. C.; Calderon, S. N.; Rothman, R. B.; Yamamura, H. I.; Davis, P.; Flippen-Anderson, J. L.; Xu, H.; et al. Probes for narcotic receptor-mediated phenomena: Synthesis and evaluation of N-alkyl-substituted (alphapiperazinylbenzyl) benzamides as novel, highly selective delta opioid receptor agonists. J. Med. Chem. 1997, 40, 2936-2947.
83. Maddaford, S. P.; Andersen, N. G.; Cristofoli, W. A.; Keay, B. A. Total synthesis of (+)-xesloquinone using an asymmetric palladium-catalyzed polyene cyclization. J. Am. Chem. Soc. 1996, 118, 10766.
84. Murray, W. M.; Semple, J. E. Facile access to novel 1,4-dihydro- xynapththalene-2,3-dicarboximides and heterofused analogs. Synthesis 1996, 1180-1182.