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Synlett 2011(9): 1268-1272  
DOI: 10.1055/s-0030-1260553
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Nano Copper Oxide Catalyzed Synthesis of Symmetrical Diaryl Selenides via Cascade Reaction of KSeCN with Aryl Halides

K. Harsha Vardhan Reddy, V. Prakash Reddy, B. Madhav, J. Shankar, Y. V. D. Nageswar*
Organic Chemistry Divison-I, Indian Institute of Chemical Technology, Hyderabad 500 607, India
e-Mail: dryvdnageswar@gmail.com;
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Publikationsverlauf

Received 26 January 2011
Publikationsdatum:
05. Mai 2011 (online)

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Abstract

An unprecedented transfer of selenium ion from potassium selenocyanate was observed in C-Se cross-coupling reaction catalyzed by copper oxide nanoparticles under ligand-free conditions. Utilizing this protocol wide range of symmetrical diaryl selenides were obtained in excellent yields. Nano-CuO is recyclable up to four cycles without loss of catalytic activity.

Key words

aryl halides - potassium selenocyanate - cross-coupling - nano copper oxide - ligand-free conditions - recyclable

17

General Procedure for the Synthesis of Diaryl Selenides
To a stirred solution of aryl halides (2.0 mmol) and potassium selenocyanate (1.2 equiv) in dry DMSO (2.0 mL) at r.t. was added nano-CuO (5.0 mol%) followed by KOH (2.0 equiv) and heated at 110 ˚C for 15 h. The progress of the reaction was monitored by TLC. After the reaction was complete, the reaction mixture was allowed to cool, and a 1:1 mixture of EtOAc-H2O (20 mL) was added. The combined organic extracts were washed with brine and H2O and dried with anhyd Na2SO4. The solvent and volatiles were completely removed under vacuum to give the crude product, which was purified by column chromatography on silica gel (PE-EtOAc) to afford the corresponding coupling product in excellent yields.
Recycling of the Catalyst After the reaction was complete, the reaction mixture was allowed to cool, a 1:1 mixture of EtOAc- H2O (2.0 mL) was added, and CuO was removed by centrifugation. After each cycle, the catalyst was recovered by simple centrifugation, washing with deionized H2O and EtOAc and then drying in vacuo. The recovered nano-CuO was used directly in the next cycle. Dinaphthalen-1-ylselane (Table 2, Entry 11) Yellow liquid. IR (neat): ν = 3091, 2928, 1588, 1390, 1077, 968, 848 cm-¹. ¹H NMR (200 MHz, CDCl3, TMS): δ = 8.05-8.02 (m, 4 H), 7.79-7.65 (m, 4 H), 7.55-7.40 (m, 4 H), 7.15 (t, 2 H, J = 7.93Hz). ¹³C NMR (50 MHz, CDCl3, TMS): δ = 137.2, 133.9, 131.9, 128.8, 128.3, 127.5, 126.6, 125.6. ESI-MS: m/z = 335 [M + 1]. Anal. Calcd for C20H14Se(334): C, 72.07; H, 4.23. Found: C, 72.01; H, 4.18.
Bis[4-(benzyloxy)phenyl]selane (Table 2, Entry 13) Colorless oil. IR (neat): ν = 3099, 2923, 1598, 1397, 1081, 961, 842 cm-¹. ¹H NMR (200 MHz, CDCl3, TMS): δ = 7.51 (d, 4 H, J = 9.16 Hz), 7.39-7.25 (m, 10 H), 6.70 (d, 4H, J = 9.16 Hz), 5.02 (s, 4 H). ¹³C NMR (50 MHz, CDCl3, TMS): δ = 158.63, 138.35, 136.35, 128.52, 128.11, 127.30, 117.53, 69.87. ESI-MS: m/z = 447 [M + 1]. Anal. Calcd for C26H22O2Se(446): C, 70.11; H, 4.98. Found: C, 70.04; H, 4.91.
Dipyridin-3-ylselane (Table 2, Entry 18) ¹H NMR (200 MHz, CDCl3): δ = 8.69 (s, 2 H), 8.58-8.52 (m, 2 H), 7.73 (d, 2 H, J = 7.93 Hz), 7.25-7.19 (m, 2 H). ¹³C NMR (50 MHz, CDCl3, TMS): δ = 153.3, 148.9, 140.6, 124.4. ESI-MS: m/z = 237 [M + 1]. Anal. Calcd for C10H8N2Se(236): C, 51.08; H, 3.43; N, 11.91. Found: C, 51.14; H, 3.46; N, 11.95. Dipyrimidin-5-ylselane (Table 2, Entry 20) Colorless oil. IR (neat): ν = 3092, 2960, 1597, 1444, 1068, 865, 738 cm-¹. ¹H NMR (200 MHz, CDCl3, TMS): δ = 7.51 (s, 2 H), 7.25 (s, 4 H). ¹³C NMR (50 MHz, CDCl3, TMS):
δ = 132.9, 129.0, 127.5. ESI-MS: m/z = 239 [M + 1]. Anal. Calcd for C8H6N4Se(238): C, 40.52; H, 2.55; N, 23.63. Found: C, 40.46; H, 2.45; N, 23.57.