Synlett 2009(2): 233-236  
DOI: 10.1055/s-0028-1087519
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Application of an Intramolecular Stetter Reaction to Access trans,syn,trans-Fused Pyrans

Christopher S. P. McErlean*a, Anthony C. Willisb
a School of Chemistry, The University of Sydney, Sydney, NSW 2006, Australia
Fax: +61(2)93513329; e-Mail: C.McErlean@chem.usyd.edu.au;
b Research School of Chemistry, The Australian National University, Canberra, ACT 0200, Australia
Further Information

Publication History

Received 19 September 2008
Publication Date:
15 January 2009 (online)

Abstract

The use of a commercially available thiazolium salt facilitated an intramolecular Stetter reaction between an aliphatic aldehyde and an acrylate unit, which delivered a trans,syn-fused bicyclic pyranone in high yield as a single diastereomer. The pyranone was used to synthesize a trans,syn,trans-fused polycyclic ether array and was ring expanded to give the corresponding oxepanone.

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Synthesis of Compound 8
To a solution of aldehyde 7 (58 mg, 0.24 mmol) in THF (2 mL) was added thiazolium salt 11 (90 mg, 0.36 mmol) and DBU (54 µL, 0.36 mmol). The mixture was stirred under reflux for 16 h, poured onto H2O (30 mL), and extracted with EtOAc (4 × 10 mL). The combined organic phases were dried over Na2SO4, the solvent was evaporated, and the residue was subjected to flash chromatography, eluting with 10% EtOAc in hexanes, to give 8 (57 mg, 98%) as a clear oil. IR (CHCl3): νmax = 3093, 2977, 2931, 1735, 1720, 1450, 1396, 1288, 1172, 1103, 1026 cm. ¹H NMR (300 MHz, CDCl3): δ = 4.29 (1 H, dd, J = 6.0, 5.7 Hz), 4.14 (2 H, q, J = 7.2 Hz), 3.36 (1 H, ddd, J = 9.9, 9.9, 4.5 Hz), 2.87 (1 H, dd, J = 16.5, 5.4 Hz), 2.62 (1 H, dd, J = 16.5, 6.3 Hz), 2.55 (1 H, dd, J = 15.5, 4.5 Hz), 2.15 (1 H, dd, J = 15.5, 12.3 Hz), 2.05-1.99 (1 H, m), 1.85-1.62 (4 H, m), 1.37-1.06 (4 H, m), 1.25 (3 H, t, J = 7.2 Hz). ¹³C NMR (75.4 MHz, CDCl3): δ = 206.6 (C), 171.0 (C), 80.5 (CH), 79.7 (CH), 60.7 (CH2), 45.1 (CH2), 42.9 (CH), 35.3 (CH2), 32.0 (CH2), 31.7 (CH2), 24.9 (CH2), 24.6 (CH2), 14.2 (CH3). HRMS: m/z calcd for C13H21O4 [M + H+]: 241.14344; found: 241.14383.