Synlett 2004(14): 2545-2548  
DOI: 10.1055/s-2004-832841
LETTER
© Georg Thieme Verlag Stuttgart · New York

Diastereoselective Synthesis of Seven- and Eight-Membered Oxabicycles via Prins-Type Cyclization

Hyun Jung Kanga, Sang Hee Kima, Ae Nim Paea, Hun Yeong Koha, Moon Ho Changa, Kyung il Choia, So-Yeop Hanb, Yong Seo Cho*a
a Biochemicals Research Center, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul 130-650, Korea
Fax: +82(2)9585189; e-Mail: ys4049@kist.re.kr;
b Division of Molecular Life Sciences, Ewha Womans University, 1-1 Daehyun-dong, Seodaemun-gu, Seoul, 120-750, Korea
Further Information

Publication History

Received 28 June 2004
Publication Date:
24 September 2004 (online)

Abstract

A novel methodology for the diastereoselective synthesis of seven- and eight-membered oxabicycles bearing dimethylidene via Prins-type cyclization was developed. The reaction takes place in the presence of TMSOTf in diethyl ether at -78 °C.

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A General Procedure for Preparation of Seven- and Eight-Membered Oxabicycles:
To a stirred solution of allenol substrates 1 (or 2) (0.36 mmol) in dry Et2O (3.0 mL) was added TMSOTf (0.36 mmol) at -78 °C. The mixture was allowed to warm to r.t. slowly for 3 h, then stirred at r.t. for 0.5-1 h until completion of the reaction. The reaction mixture was diluted with 10 mL of Et2O, and then H2O (4mL) was added. The organic solution was washed with brine, and the organic layer was dried (MgSO4), filtered, and concentrated. Purification by flash column chromatography provided the desired cycloadducts. Compound 5a: 1H NMR (300 MHz, CDCl3): δ = 5.00 (s, 1 H), 5.29 (s, 1 H), 4.78 (t, 2 H, J = 5.6 Hz), 4.53 (br s, 1 H), 2.69 (br d, 1 H, J = 12.1 Hz), 2.00-2.36 (m, 2 H), 1.64-1.85 (m, 3 H), 1.51 (s, 3 H). 13C NMR (75 MHz, CDCl3): δ = 152.51, 143.41, 112.19, 104.33, 81.86, 76.23, 42.42, 37.47, 30.22, 22.87 ppm. IR (KBr): 2926, 1731, 1458 cm-1. GC-MS: m/z = 150 [M+]. HRMS: m/z calcd for C10H14O: 150.1045; found: 150.1043. Compound 6a: 1H NMR (300 MHz, CDCl3): δ = 5.25 (s, 1 H), 5.13 (s, 1 H), 4.80 (s, 1 H), 4.74 (s, 1 H), 4.23 (br t, 1 H, J = 6.3 Hz), 2.00-1.25 (m, 8 H), 1.35 (s, 3 H). 13C NMR (75 MHz, CDCl3): δ = 152.3, 146.1, 109.2, 107.6, 74.0, 69.2, 40.3, 38.6, 30.5, 29.1, 17.9 ppm. IR (KBr): 2924, 1730, 1454 cm-1. GC-MS: m/z = 164 [M+]. HRMS: m/z calcd for C11H16O: 164.1200; found: 164.1201.