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Issue 17, 1997
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Synthesis of fused furans by gas-phase pyrolysis of 2-allyloxyarylpropenoic esters 1

Abstract

Flash vacuum pyrolysis of 2-allyloxypropenoic esters (e.g. 7) gives benzo[b]furans (e.g. 32) in synthetically useful yields by sequential generation of a phenoxyl radical, cyclisation and ejection of the carboxylic ester function as a free radical leaving group. The method is compatible with a range of substituents on either the benzene ring or the propenoate chain, and is particularly effective for 2-substituted benzo[b]furans. The natural products 5-methoxybenzo[b]furan 1 and angelicin 2 have been synthesised in three and four steps respectively from commercially available starting materials by this route. Related cyclisations to give naphtho[2,1-b]furan 40 were complicated by competitive formation of naphtho[2,1-b]pyran-3-ones (e.g. 41 and 42), but the yield of the required product could be optimised by the choice of the radical precursor. Annelation of a furan ring onto a thiophene is also possible by this method, but lower yields are obtained in such pyrolyses.

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Article information


J. Chem. Soc., Perkin Trans. 1, 1997, 2483-2494
Article type
Paper

Synthesis of fused furans by gas-phase pyrolysis of 2-allyloxyarylpropenoic esters 1

M. Black, J. I. G. Cadogan, H. McNab, A. D. MacPherson, V. Peter Roddam, C. Smith and H. R. Swenson, J. Chem. Soc., Perkin Trans. 1, 1997, 2483
DOI: 10.1039/A702451G

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