PDF herunterladen
Synlett 2011(3): 415-419  
DOI: 10.1055/s-0030-1259313
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Fe(OTf)3-Catalyzed Reaction of Benzylic Acetates with Organosilicon Compounds

Li Yan Chan, Sundae Kim, Wan Ting Chung, Chong Long, Sunggak Kim*
Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
Fax: +6567911961; e-Mail: sgkim@ntu.edu.sg;
Weitere Informationen

Publikationsverlauf

Received 20 October 2010
Publikationsdatum:
13. Januar 2011 (online)

    Lizenzen und Reprints Alle Artikel dieser Rubrik

Abstract

Fe(OTf)3-catalyzed reaction of benzylic acetates with allyltrimethylsilane, azidotrimethylsilane, and cyanotrimethylsilane afforded the corresponding allylated, azido, and cyano products in high yields. 2-Trimethylsilyl-substituted benzofuran and indole worked well to furnish the benzyl-substituted benzofuran and indoles.

Key words

iron-catalyzed reaction - allylation - azidation - cyanation - benzylic acetates - organosilanes

14

Reaction of(methoxymethylene)dibenzene (Ph2CHOMe) with allyltrimethylsilane in the presence of 5 mol% Fe(OTf)3 in DCE at r.t. for 5 h afforded 4a (73%) but the allylation of 3 did not occur, even under prolonged heating at 80 ˚C.

15

Fe(OTf)3 was prepared from 5 mol% FeCl3 and 15 mol% AgOTf in DCE. Filtration was done to remove the AgCl precipitate, and the catalyst was used to repeat the allylation. The reaction time and yield observed were comparable to the Fe(OTf)3 generated in situ without filtration. For instance, the allylation of 4 under the similar conditions afforded 4a in 89% yield.

17

General Procedure for the Reaction of Benzylic Acetates with Organosilanes: But-3-ene-1,1-diyldibenzene (4a)
Anhydrous FeCl3 (2.4 mg, 0.015 mmol) and AgOTf (11.5 mg, 0.045 mmol) was carefully weighed inside a glove box and stirred in DCE (2 mL) for 5 min. Allyl trimethylsilane (41.1 mg, 0.36 mmol) and benzhydryl acetate 4 (67.9 mg, 0.3 mmol) were then added to the prepared catalyst solution and stirred for 0.5 h at r.t. The residual crude product was concentrated in vacuo and purified by silica gel column chromatography using n-hexane as eluent to afford the desired product 4a (60.0 mg, 96% yield). ¹H NMR (400 MHz, CDCl3): δ = 7.29-7.23 (m, 8 H), 7.19-7.15 (m, 2 H), 5.75-5.68 (m, 1 H), 5.05-4.93 (m, 2 H), 4.01 (t, J = 7.8 Hz, 1 H), 2.84-2.80 (m, 2 H). ¹³C NMR (100 MHz, CDCl3): δ = 144.5, 136.8, 128.4, 127.9, 126.2, 116.3, 51.2, 39.9.

18

¹ H NMR and ¹³ C NMR Data of Previously Unknown Compounds
2-Benzhydryl-1-methyl-1 H -indole (4g)
¹H NMR (400 MHz, CDCl3): δ = 7.29-7.17 (m, 13 H), 6.97 (t, J = 7.6 Hz, 1 H), 6.40 (s, 1 H), 5.66 (s, 1 H), 3.68 (s, 1 H). ¹³C NMR (100 MHz, CDCl3): δ = 144.1, 137.4, 129.0, 128.7, 128.2, 127.3, 126.1, 121.6, 120.0, 118.8, 118.2, 109.1, 48.8, 32.6. HRMS (EI+): m/z calcd for C22H20N [M + 1]: 298.1596; found: 298.1603.
2-(4-Methoxybenzyl)-1-methyl-1 H -indole (6d)
¹H NMR (400 MHz, CDCl3): δ = 7.51 (d, J = 7.6 Hz, 1 H), 7.29-7.18 (m, 4 H), 7.06 (t, J = 7.4 Hz, 1 H), 6.82 (d, J = 8.4 Hz, 2 H), 6.72 (s, 1 H), 4.04 (s, 2 H), 3.77 (s, 3 H), 3.71 (s, 3 H). ¹³C NMR (100 MHz, CDCl3): δ = 157.7, 137.1, 133.5, 129.5, 127.8, 127.0, 121.5, 119.2, 118.7, 114.7, 113.7, 109.1, 55.2, 32.6, 30.6, 29.2. HRMS (EI+): m/z calcd for C22H20N [M + 1]: 252.1388; found: 252.1393.
( E )-2-(1,3-Diphenylallyl)-1-methyl-1 H -indole (9d)
¹H NMR (400 MHz, CDCl3): δ = 7.42 (d, J = 8.0 Hz, 1 H), 7.37-7.18 (m, 13 H), 7.01 (t, J = 7.4 Hz, 1 H), 6.74-6.69 (m, 2 H), 6.43 (d, J = 16.0 Hz, 1 H), 5.11 (d, J = 7.6 Hz, 1 H), 3.72 (s, 3 H). ¹³C NMR (100 MHz, CDCl3): δ = 143.5, 137.5, 137.4, 132.7, 130.4, 128.4, 127.3, 127.2, 127.1, 126.3, 121.6, 120.0, 118.8, 117.0, 109.2, 46.1, 32.7. HRMS (EI+): m/z calcd for C24H22N [M + 1]: 324.1752; found: 324.1746.