Synlett 2004(11): 1933-1936  
DOI: 10.1055/s-2004-830857
LETTER
© Georg Thieme Verlag Stuttgart · New York

A Convenient Synthesis of Highly Substituted Furans by Microwave Irradiation of Ring-Fused Alkylidenecyclopropanes

Morshed Alam Chowdhury, Hisanori Senboku, Masao Tokuda*
Laboratory of Organic Synthesis, Division of Molecular Chemistry, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan
Fax: +81(11)7064889; e-Mail: tokuda@org-mc.eng.hokudai.ac.jp;
Further Information

Publication History

Received 21 April 2004
Publication Date:
28 July 2004 (online)

Abstract

Microwave irradiation of ring-fused alkylidenecyclopropanes under solvent-free conditions afforded highly substituted furans in good yields.

21

General procedure for microwave reaction is as follows: Alkylidenecyclopropane 1 (300 mg) was taken in a ground-joint test-tube with a stir bar. It was placed in the microwave oven and equipped with a condenser. Simple microwave reaction apparatus, Model No. SMW-05, 650 W, Shikoku Keisoku Kogyo Co. Ltd., Japan, was used. Irradiation was carried out with stirring for 5 min. After cooling to r.t., the product was purified by column chromatography on silica gel, eluting with n-hexane to give pure products. All new products were characterized fully by 1H NMR, 13C NMR and HRMS or elemental analyses.
Selected data of 3-methyl-2-phenyl-5,6,7,8-tetrahydro-4H-cyclohepta[b]furan (2d): 1H NMR (270 MHz, CDCl3): δ = 1.65-1.85 (m, 6 H), 2.13 (s, 3 H), 2.41 (t, J = 5.9 Hz, 2 H), 2.80 (t, J = 5.9 Hz, 2 H), 7.18 (t, J = 7.6 Hz, 1 H), 7.36 (t, J = 7.6 Hz, 2 H), 7.57 (d, J = 8.3 Hz, 2 H). 13C NMR (67.5 MHz): δ = 9.83, 23.67, 26.53, 28.49, 28.93, 30.82, 117.32, 123.24, 125.11, 125.94, 128.35, 132.26, 145.14, 152.22. EIMS: m/z (rel. intensity) = 226 (100) [M+], 211 (11), 197 (18), 184 (11), 172 (28), 155 (6), 141 (6), 105 (7), 77 (8). HRMS: m/z calcd for C16H18O: 226.1358. Found: 226.1351.
Selected data of 3-methyl-2-phenyl-4,5,6,7,8,9-hexahydrocycloocta[b]furan (4d): 1H NMR (270 MHz, CDCl3): δ = 1.40-1.60 (m, 4 H), 1.60-1.80 (m, 4 H), 2.14 (s, 3 H), 2.50 (t, J = 6.3 Hz, 2 H), 2.79 (t, J = 6.3 Hz, 2 H), 7.18 (t, J = 7.6 Hz, 1 H), 7.36 (t, J = 7.6 Hz, 2 H), 7.59 (d, J = 7.3 Hz, 2 H). 13C NMR (67.5 MHz): δ = 9.70, 21.53, 25.60, 25.81, 26.15, 27.97, 28.21, 116.92, 120.97, 124.89, 125.83, 128.35, 132.38, 145.76, 150.61. EIMS: m/z (rel. intensity) = 240 (100) [M+], 212 (58), 197 (30), 185 (42), 172 (23), 155 (11), 141 (14), 105 (21), 77 (26). HRMS: m/z calcd for C17H20O: 240.1514. Found: 240.1511. Anal. Calcd for C17H20O: C, 84.96; H, 8.39. Found: C, 85.02; H, 8.39.