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Synlett 2009(14): 2265-2268  
DOI: 10.1055/s-0029-1217804
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

An Economical Noncatalytic Approach to the Synthesis of Congested Diaryl Ethers and Aryl Benzyl Thioethers through C-C Insertion

Farhanullah, Vishnu ji Ram*
Department of Applied Chemistry, Institute of Engineering and Technology, Sitapur Road, Lucknow 226020, India, Fax: +91(522)2623405; e-Mail: vjiram@yahoo.com;
Fax: +65 6779 1691; e-Mail: farhanullah73@yahoo.com;
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Publikationsverlauf

Received 15 May 2009
Publikationsdatum:
07. August 2009 (online)

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Abstract

An efficient one-pot synthesis of diaryl ethers and aryl benzyl thioethers has been delineated through base-induced ring transformation of 6-aryl-4-methylthio-2H-pyran-2-one-3-carbo­nitriles, methyl 6-aryl-4-methylthio-2H-pyran-2-one-3-carboxylates and 6-aryl-4-(piperidin-1-yl)-2H-pyran-2-one-3-carbonitriles by either 1-phenoxypropan-2-one, 1,3-diphenoxypropan-2-one or 4-arylthiobutan-2-one, under very mild reaction conditions, in excellent yield.

Key words

6-aryl-4-methylthio-2H-pyran-2-one-3-carbonitriles - ring transformation - diaryl ethers - 1,3-diphenoxypropan-2-one

25

General procedure for the synthesis of 5-methylthio-2-phenoxy-3-(phenoxymethyl)biphenyl-4-carbonitriles/carboxylates (3d-h): An equimolar mixture of 1 and 2b and powdered KOH in DMF was stirred for 2-3 h. During this period, evolution of carbon dioxide bubbles ceased and starting materials were consumed completely (reaction monitored by TLC). The reaction mixture was poured into ice-cold H2O with vigorous stirring. The precipitate thus obtained was filtered and purified by silica gel column chromatography to give the product in 68-86% yield. Compound 3d: mp 133-135 ˚C. IR (KBr): 2212 (CN) cm-¹; ¹H NMR (200 MHz, CDCl3): δ = 2.60 (s, 3 H), 5.13 (s, 2 H), 6.59 (d, J = 8.70 Hz, 2 H), 6.83-6.93 (m, 4 H), 7.03-7.08 (m, 2 H), 7.19-7.28 (m, 5 H), 7.36-7.41 (m, 3 H); MS (FAB): m/z = 424 [M+ + 1]; Anal. Calcd for C27H21NO2S: C, 76.57; H, 5.00; N, 3.31. Found: C, 76.66; H, 5.18; N, 3.42. Compound 3e: mp 152-154 ˚C. IR (KBr): 2210 (CN) cm-¹; ¹H NMR (200 MHz, CDCl3): δ = 2.61 (s, 3 H), 5.11 (s, 2 H), 6.56 (d, J = 8.70 Hz, 2 H), 6.82-6.96 (m, 3 H), 7.06-7.09 (m, 2 H), 7.19-7.28 (m, 4 H), 7.36 (d, J = 8.70 Hz, 2 H), 7.65 (d, J = 8.70 Hz, 2 H); MS (FAB): m/z = 503 [M+ + 1]; Anal. Calcd for C27H20BrNO2S: C, 64.55; H, 4.01; N, 2.79. Found: C, 64.65; H, 4.16; N, 2.90. Compound 3f: mp 154-156 ˚C. IR (KBr): 1768 (CO2Me) cm-¹; ¹H NMR (200 MHz, CDCl3): δ = 2.51 (s, 3 H), 3.83 (s, 3 H), 5.07 (s, 2 H), 6.62 (d, J = 8.80 Hz, 2 H), 6.82-6.96 (m, 4 H), 7.06-7.09 (m, 2 H), 7.19-7.28 (m, 6 H), 7.36-7.39 (m, 2 H); MS (FAB): m/z = 457 [M+ + 1]; Anal. Calcd for C28H24O4S: C, 73.66; H, 5.30; Found: C, 73.77; H, 5.22. Compound 3g: mp 144-146 ˚C. IR (KBr): 1764 (CO2Me) cm-¹; ¹H NMR (200 MHz, CDCl3): δ = 2.56 (s, 3 H), 3.80 (s, 3 H), 5.13 (s, 2 H), 6.76 (d, J = 7.60 Hz, 2 H), 6.89-6.99 (m, 3 H), 7.02-7.05 (m, 1 H), 7.11-7.16 (m, 2 H), 7.21-7.31 (m, 5 H), 7.47 (d, J = 7.60 Hz, 2 H); MS (FAB): m/z = 536 [M+ + 1]; Anal. Calcd for C28H23BrO4S: C, 62.81; H, 4.33. Found: C, 62.77; H, 4.44. Compound 3h: mp 138-140 ˚C. IR (KBr): 2210 (CN) cm-¹; ¹H NMR (200 MHz, CDCl3): δ = 1.62-1.64 (m, 2 H), 1.81-1.82 (m, 4 H), 3.20 (t, J = 4.8 Hz, 4 H), 5.09 (s, 2 H), 6.56 (d, J = 9.0 Hz, 2 H), 6.83-6.95 (m, 4 H), 7.01-7.19 (m, 3 H), 7.21-7.30 (m, 4 H), 7.38-7.41 (m, 2 H); MS (FAB): m/z = 540 [M+ + 1]; Anal. Calcd for C31H27BrN2O2: C, 69.02; H, 5.04; N, 5.19. Found: C, 69.18; H, 5.26; N, 5.29. Synthesis of 3-methylthio-5-methyl-6-(4-methylphenylthio-ethyl)biphenyl-4-carbonitrile (6): A mixture of 2-pyranone 1 (1 mmol), 4-arylthiobutan-2-one 5 (1.2 mmol) and pow-dered KOH (1.5 mmol) in anhydrous DMF (8 mL) was stirred at r.t. for 5 h. The reaction mixture was poured onto crushed ice with vigorous stirring and neutralized with 10% HCl. The precipitate obtained was filtered, washed with H2O and finally purified by silica gel column chromatography to afford 6 in moderate yield (52%). Mp 90-92 ˚C. IR (KBr): 2214 (CN) cm-¹; ¹H NMR (200 MHz, CDCl3): δ = 2.31 (s, 3 H), 2.51 (s, 3 H), 2.70 (s, 3 H), 3.94 (s, 2 H), 6.97 (s, 1 H), 7.01-7.11 (m, 4 H), 7.37-7.39 (m, 5 H); MS (FAB): m/z = 376 [M+ + 1]; Anal. Calcd for C23H21NS2: C, 73.56; H, 5.64; N, 3.73. Found: C, 73.18; H, 5.52; N, 4.06.