ORGANIC
LETTERS
2010
Vol. 12, No. 18
4192-4194
New Cyclization of
4-Oxahepta-1,6-diynes Bearing Sulfur
and Selenium Functional Groups
Mitsuhiro Yoshimatsu,* Hiroyasu Watanabe, and Eri Koketsu
Department of Chemistry, Faculty of Education, Gifu UniVersity,
1-1 Yanagido, Gifu 501-1193, Japan
Received July 7, 2010
ABSTRACT
New cyclizations of 1-sulfanyl- and -selanyl-4-oxa-1,6-heptadiynes using sodium alkoxide or thiolates provided 4-alkoxymethyl-3-phenylsulfanyl-
and 3,4-bis(sulfanylmethyl)furans in high yields.
Furans are important heterocycles found in natural products
and biologically active compounds. Accordingly, substantial
attention has been paid to discover efficient synthetic routes
to furans.1 Cycloaddition or cycloisomerization is a powerful
approach to synthesize aromatic heterocycles. The most
widely used methods for the synthesis of furans proceed via
cycloisomerization of alkynyl and allenyl ketones.2 Alterna-
tive approaches to the synthesis of substituted furans involve
a similar cyclization of the corresponding alcohols or
epoxides.3 The practical applicability of these methods
depends on the ease of access to alkynyl and allenyl
precursors and the precursor’s stability under the isomer-
ization conditions.4 In general, alkynes are better starting
materials because of the easy interconversion of alkyne to
allenes under basic conditions.5 Numerous strategies for the
synthesis of furans from alkynyl ketones, alcohols, and
epoxides exist; however, annulation of 4-oxahepta-1,6-diynes
has been limited.6 While searching for new strategies based
upon the concept of a simple cyclization using nontransition
metals, we investigated the cyclization of 4-oxahepta-1,6-
diynes (bispropargyl ethers), which easily convert to allenic
ethers under basic conditions. However, the cyclization of
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10.1021/ol101540s 2010 American Chemical Society
Published on Web 08/26/2010