Synthesis 2010(22): 3855-3864  
DOI: 10.1055/s-0030-1258265
PAPER
© Georg Thieme Verlag Stuttgart ˙ New York

3-Alkoxy-2,5-dihydrofurans by Gold-Catalyzed Allenyl Cyclizations and Their Transformation into 1,4-Dicarbonyl Compounds, Cyclopentenones, and Butenolides

Malte Brasholz, Branislav Dugovič, Hans-Ulrich Reissig*
Institut für Chemie und Biochemie, Freie Universität Berlin, Takustr. 3, 14195 Berlin, Germany
Fax: +49(30)83855367; e-Mail: hans.reissig@chemie.fu-berlin.de;
Further Information

Publication History

Received 7 July 2010
Publication Date:
24 September 2010 (online)

Abstract

The addition of lithiated alkoxyallenes to carbonyl compounds furnishes allenyl alcohols, which undergo a highly efficient and chemoselective 5-endo-trig cyclization to 3-alkoxy-2,5-dihydrofurans catalyzed by gold(I) chloride. The dihydrofurans produced can be either oxidized to β-alkoxy butenolides by a manganese(III) acetate catalyzed radical oxidation with tert-butyl hydroperoxide, or transformed into α,β-unsaturated γ-keto aldehydes by an oxidative ring cleavage using DDQ in the presence of water. Treatment of the γ-keto aldehydes with sodium methoxide in methanol promotes a diastereoselective intramolecular aldol addition furnishing alkoxy-substituted cyclopentenone derivatives in good yield.

39

This was demonstrated for closely related compounds, see refs. 26b, 26c.

42

Attempted asymmetric organocatalytic variants of the reaction have so far been unsuccessful.