Synlett 2003(13): 2017-2020  
DOI: 10.1055/s-2003-42038
LETTER
© Georg Thieme Verlag Stuttgart · New York

Ring-Closing Metathesis of Enynes Tethered by an N-O Bond: Synthesis of 1,2-Oxaza Polycycles by Diels-Alder Reaction of the Ring-Closing Metathesis Products

Young-Keun Yang, Jinsung Tae*
Center for Bioactive Molecular Hybrids (CBMH), Department of Chemistry, Yonsei University, Seoul 120-749, South Korea
Fax: +82(2)3647050; e-Mail: jstae@yonsei.ac.kr;
Further Information

Publication History

Received 8 August 2003
Publication Date:
08 October 2003 (online)

Abstract

Ring-closing metathesis (RCM) reaction of enynes tethered by an N-O bond produced 6- to 8-membered 1,2-oxaza heterocyclic compounds in high yields. Diels-Alder reaction of the cyclic 1,3-dienes with various dienophiles afforded bi- or tri-cyclic compounds efficiently.

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We have observed spontaneous oxidation of compounds 18 and 19 to the corresponding aromatic compounds 30 and 32 within a few days after preparation under the standard storage conditions.

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Spectral data for 10a: Colorless oil; Rf = 0.5 (silica gel, hexane-EtOAc = 2:1). IR(film): 1701, 1603, 1394, 1368, 1240, 1163, 1092, 1045 cm-1. 1H NMR (250 MHz, CDCl3): δ = 6.33 (dd, J = 17.8, 10.9 Hz, 1 H), 5.81 (m, 1 H), 5.14 (d, J = 18.7 Hz, 1 H), 5.08 (d, J = 12.0 Hz, 1 H), 4.51-4.46 (m, 2 H), 4.25-4.20 (m, 2 H), 1.51 (s, 9 H). 13C NMR (62.9 MHz, CDCl3): δ = 155.1, 135.3, 132.4, 124.0, 112.7, 81.9, 68.2, 44.7, 28.5. HRMS: m/z (M+) calcd for C11H17NO3: 211.1208; found: 211.1206.

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Spectral data for 16: Colorless oil; Rf = 0.3 (silica gel, hexane-EtOAc = 2:1). IR(film): 1731, 1655, 1434, 1368, 1265, 1158, 1071, 1035 cm-1. 1H NMR (500 MHz, CDCl3): δ = 5.70 (s, 1 H), 4.39 (d, J = 13.8 Hz, 1 H), 4.22-4.17 (m, 1 H), 3.79 (s, 3 H), 3.77 (s, 3 H), 3.67 (t, J = 10.8 Hz, 2 H), 3.61-3.57 (m, 1 H), 3.19-3.11 (m, 1 H), 3.05-2.97 (m, 1 H), 1.49 (s, 9 H). 13C NMR (125.8 MHz, CDCl3): δ = 167.5, 167.4, 155.0, 133.2, 132.1, 128.5, 118.2, 82.0, 74.1, 52.7, 52.4, 38.0, 28.3, 27.7. HRMS: m/z (M+) calcd for C17H23NO7: 353.1475; found: 353.1485.