A New Benzannulation Reaction of Azoaromatics

Abstract

The BHQ benzannulation reaction of azo-substituted (2-allyl­aryl)trichloracetates, leading to azo-naphthalenes, is described. The scope and limitations of this new synthesis of azoaromatics is discussed.

Key words

benzannulation - ATRC - azo - cyclisation - copper - carbene - radical

• References and Notes

• 1 For applications of related compounds, see: Quandt G, Höner G, Pabel J, Dine J, Eder M, Wanner KT. J. Med. Chem. 2014; 57: 6809
• 2a Griess P. Justus Liebigs Ann. Chem. 1866; 137: 39
• 2b Maerino E. Chem. Soc. Rev. 2011; 40: 3835
• 2c Zollinger H. Azo Coupling Reactions . In Diazo Chemistry I . VCH; Weinheim: 1994: 305
• 3a Gøgsig TM, Kleimark J, Nilsson L, Korsager S, Lindhardt AT, Norrby P.-O, Skrydstrup T. J. Am. Chem. Soc. 2012; 134: 443
• 3b Casa-Solvas JM, Vargas-Berenguel A. Tetrahedron Lett. 2008; 49: 6778
• 3c Ma X, Wang Q, Tian H. Tetrahedron Lett. 2007; 48: 7112
• 3d Harvey JH, Butler BK, Trauner D. Tetrahedron Lett. 2007; 48: 1661
• 3e Okanao K, Tsutsumi O, Shishido A, Ikeda T. J. Am. Chem. Soc. 2006; 128: 15368
• 3f Liao L.-X, Stellacci F, McGrath DV. J. Am. Chem. Soc. 2004; 126: 2181

For a representative example, see:
• 3g Strueben J, Gates PJ, Staubitz A. J. Org. Chem. 2014; 79: 1719
• 3h Pérez-Miqueto J, Telleria A, Muñoz-Olasagasti M, Altube A, Garcia-Lecina E, de Cózar A, Freixa Z. Dalton Trans. 2015; 2075
• 4a Heck RF. J. Am. Chem. Soc. 1968; 90: 313
• 4b Cope AC. J. Am. Chem. Soc. 1965; 87: 3272
• 4c Kleiman JP, Dubeck M. J. Am. Chem. Soc. 1963; 85: 1544
• 4d Bagga MM, Flannigan WT, Knox GR, Pauson PL. J. Chem. Soc. C 1969; 1534
• 5a Majhi B, Kundu D, Ahammaed S, Ranu BC. Chem. Eur. J. 2014; 20: 9862
• 5b Qian C, Lin D, Deng Y, Zhang X-Q, Jiang H, Miao G, Tang X, Zeng Y. Org. Biomol. Chem. 2014; 12: 5866
• 5c Lian Y, Bergman RG, Lavis LD, Ellman JA. J. Am. Chem. Soc. 2013; 135: 7122 ; and references cited therein
• 6a Koźlecki T, Syper L, Wilk KA. Synthesis 1997; 681
• 6b Kano N, Komatsu F, Yamamura M, Kawashima T. J. Am. Chem. Soc. 2006; 128: 7097

The direct lithiation of azobenzene derivatives has recently been reported, see:
• 6c Nguyen TT. T, Boussonnière A, Banaszak E, Castanet A.-S, Nguyen KP. P, Mortier J. J. Org. Chem. 2014; 79: 2775
• 7a Colonna M, Risalti A. Gazz. Chim. Ital. 1956; 86: 698
• 7b Risaliti A, Bozzini S. Ann. Chim. 1964; 54: 685
• 7c Holm T. Acta Chem. Scand. B 1983; 37: 567
• 8a Bull JA, Hutchings MG, Quayle P. Angew. Chem. Int. Ed. 2007; 46: 1869
• 8b Bull JA, Hutchings MG, Lujan C, Quayle P. Tetrahedron Lett. 2008; 49: 1352
• 8c Bull JA, Hutchings MG, Lujan C, Quayle P. Tetrahedron Lett. 2009; 50: 3617
• 8d Little M, Lan H, Raftery J, Morrison JJ, McDouall JJ. W, Yeates SG, Quayle P. Eur. J. Org. Chem. 2013; 6038
• 8e Heard KW. J, Morrison JJ, Weston L, Lo CH, Pirvu L, Raftery J, Little MS, McDouall JJ. W, Yeates SG, Quayle P. Chem. Commun. 2015; 51: 6115

ATRP reactions of azo-containing substrates is documented:
• 8f Fang L, Chen S, Guo X, Zhang Y, Zhang H. Langmuir 2012; 28: 9767
• 9a Majumdar KC, Nandi RK. Tetrahedron 2013; 69: 6921
• 9b Ichikawa H, Maruoka K. Aliphatic and Aromatic Claisen Rearrangement . In The Claisen Rearrangement . Hiesermann M, Nubbermeyer U. Wiley-VCH; Weinheim: 2007. Chap. 3, 45
• 10a Florea S, Rudolf WD, Chivu M. Anal. Univ. Craiova, Ser. Chim. 2005; 34: 1 ; Chem. Abstr. 2005, 146, 379752

For alternative approaches to related substrates, see:
• 10b Odabaşoğlu M, Turgut G, Karadayi N, Büyükgüngör O. Dyes and Pigments 2005; 64: 271
• 11 Bender DR, Kanne D, Frazier JD, Rapoport H. J. Org. Chem. 1983; 48: 2709
• 12 Giger R, Allain R, Rey M, Dreiding AS. Helv. Chim. Acta 1970; 53: 120
• 13 For a related ipso-substitution reaction during a Claisen rearrangement, see: Anjaneyulu AS. R, Isaa BM. J. Chem. Soc., Perkin Trans. 1 1990; 993
• 14 Hegele P, Santhamma B, Schnakenburg G, Fröhlich R, Kateava O, Nieger M, Kotsis K, Neese F, Dötz KH. Organometallics 2010; 29: 672
• 15 General Method for the Preparation of Allylated Ethers 8 To a stirred mixture of powdered KOH (5 equiv) in DMSO was added the diazo compound (1 equiv). Allyl bromide (2 equiv) was then added to the mixture. The reaction mixture was stirred for 3 h at r.t. and then poured into H₂O. The organic material was extracted into CH₂Cl₂ (50 mL), and the organic layer was washed with brine (2 × 20 mL), H₂O (1 × 20 mL), dried (MgSO₄), and concentrated in vacuo. The crude product was purified by flash chromatography to give products 8a–i Synthesis of (E)-1-[2-(Allyloxy)phenyl]-2-phenyldiazene (8a) Yield 94%; mp 70–72 °C. ¹H NMR (300 MHz, CDCl₃): δ = 4.64 (2 H, dt, J = 5, 1 Hz), 5.34 (1 H, dq, J = 10, 1 Hz), 5.47 (1 H, dq, J = 17, 2 Hz), 5.95–6.23 (1 H, m) 6.97–7.14 (2 H, m), 7.40–7.58 (3 H, m), 7.81–8.01 (4 H, m) ppm. ¹³C NMR (75 MHz, CDCl₃): δ = 69.1, 114.9, 118.1, 122.5, 124.6, 128.9, 130.3, 132.7, 147.1, 152.7, 161.1 ppm. MS (ES⁺): m/z = 239 [M + Na]⁺. HRMS (ES⁺): m/z calcd for [C₁₅H₁₄N₂O + H]: 239.1179; found: 239.1182. IR (ATR): ν_max = 1496, 1579, 1598, 3023 cm^–1.
• 16 General Procedure for the Preparation of o-Claisen-Rearranged Phenols 9 To a stirred solution of the allyl ether (1 mmol) in dry CH₂Cl₂ (10 mL) was added Et₂AlCl (2 equiv) at 0 °C under an atmosphere of dry nitrogen. The reaction mixture was stirred at r.t. for 15 h and then quenched by the careful addition of a sat. solution of Na/K tartrate tetrahydrate (10 mL). The organic layer was separated and the aqueous phase extracted with EtOAc (2 × 20 mL). The combined organic extracts were washed (brine, 3 × 20 mL), then H₂O (3 × 20 mL), and dried over MgSO₄. The crude mixture was purified by column chromatography (40% CH₂Cl₂ in hexane) to give the products 9a–h. (E)-2-Allyl-4-(phenyldiazenyl)phenol (9a) Yield 83%; crystalline; mp 91.7–93.0 °C (lit. 89–90 °C) was obtained by column chromatography (40% CH₂Cl₂ in hexane). ¹H NMR (300 MHz, CDCl₃): δ = 3.52 (2 H, d, J = 6 Hz), 5.21 (1 H, t, J = 1 Hz), 5.26 (1 H, dd, J = 8, 1 Hz), 6.09 (1 H, ddt, J =16, 10, 6 Hz), 6.94 (1 H, dd, J = 9, 3 Hz, CH, ArH), 7.44–7.56 (3 H, m, CH, ArH), 7.76–7.82 (2 H, m, CH, ArH), 7.89 (2 H, dd, J = 8, 2 Hz, CH, ArH) ppm. ¹³C NMR (75 MHz, CDCl₃): δ = 35.1, 116.2, 117.1, 122.5, 123.5, 125.1, 129.1, 130.3, 135.7, 126.1, 147.1, 152.7, 156.9 ppm. MS (ES⁺): m/z = 239 [M + H]⁺. MS (ES^–): m/z = 237 [M – H]⁺. HRMS (ES^–): m/z calcd for [C₁₅H₁₄N₂O – H]: 237.1025; found: 237.1033. IR (ATR): ν_max = 1339, 1444, 1465, 1502, 1592, 1737, 3068 cm^–1.
• 17 General Procedure for Trichloroacylation (10) To the stirred solution of 9 (1 equiv) and Et₃N (1.2 equiv) in dry Et₂O was added dropwise trichloroacetyl chloride (1.2 equiv) at 0 °C. After 3 h at this temperature the reaction mixture was quenched by the addition of H₂O (20 mL). The quenched reaction mixture was extracted with Et₂O (50 mL), and the organic layer was separated, washed [NaHCO₃; 3 × 20 mL of a sat. solution), brine (3 × 20 mL), and H₂O (3 × 20 mL)], dried (MgSO₄), and concentrated in vacuo to afford the crude products 10a–h, which were of sufficient purity to be used in the next step. (E)-2-Allyl-4-(phenyldiazenyl)phenyl 2,2,2-Trichloroacetate (10a) Brownish oil; 81% yield. ¹H NMR (300 MHz, CDCl₃): δ = 3.50 (2 H, dd, J = 6, 1 Hz), 5.15 (1 H, dq, J = 8, 1 Hz), 5.19 (1 H, m), 5.92–6.07 (1 H, m), 7.35 (1 H, dd, J = 7, 2 Hz), 7.51–7.55 (3 H, m, CH), 7.87–7.97 (4 H, m, CH, ArH) ppm. ¹³C NMR (75 MHz, CDCl₃): δ = 34.1, 117.3, 121.8, 122, 122.9, 125.4, 129.1, 131.3, 134.7, 132.9, 151.2, 150.2, 152.5, 160.2 ppm. IR (ATR): ν_max = 1351, 1459, 1487, 1541, 1584, 1401, 1799, 2984 cm^–1.
• 18 General Procedure for Benzannulation Reactions (11) The trichloroacetate (0.5 mmol, 1 equiv) was heated with the catalyst 12 (5 mol%) in diglyme (0.5 mL) at 162 °C for 3 h under an atmosphere of dry nitrogen. The reaction mixture was allowed to cool to r.t. and then purified directly by flash column chromatography (100% PE) to give the products 11a–g. (E)-1-(5-Chloronaphthalen-2-yl)-2-phenyldiazene (11a) Yield 78%; orange crystals; mp 113–114 °C. ¹H NMR (300 MHz, CDCl₃): δ = 7.41–7.59 (4 H, m, CH, ArH), 7.66 (1 H, dd, J = 7, 1 Hz, CH, ArH), 7.89–8.04 (3 H, m, CH, ArH), 8.18 (1 H, dd, J = 9, 2 Hz, CH, ArH), 8.38 (1 H, d, J = 9 Hz, CH, ArH), 8.48 (1 H, d, J = 2 Hz, CH, ArH) ppm. ¹³C NMR (75 MHz, CDCl₃): δ = 118.6, 122.9, 125.7, 126.7, 127.2, 127.6, 128.5, 129.2, 131.2, 131.9, 132.1, 132.8, 150.6, 152.6 ppm. MS (ES⁺): m/z = 267 [M + H]⁺. HRMS (ES⁺): m/z calcd for [C₁₆H₁₁N₂Cl + H]: 267.0684; found: 267.0674. Anal. Calcd (%) for C₁₆H₁₁N₂Cl: C, 72.0; H, 4.1; N, 10.5. Found: C, 71.8; H, 4.0; N, 10.3%. IR (ATR): ν_max = 1286, 1334, 1415, 1457, 1570, 3011 cm^–1.