Albert Padwa,* Carolyn A. Leverett and Xuechuan Hong
Department of Chemistry, Emory University, Atlanta, Georgia USA
* Corresponding author: E-mail: chemap@emory.edu
Abstract
E-Dimethyl 2-(2-oxycyclopentylidene)succinate was prepared by the TiCl4
catalyzed [2+2]-cycloaddition of (trimethylsilyloxy)cyclopentene with DMAD followed by a base induced ring opening of the initially
formed cycloadduct. It was
necessary to protect the keto group as the 1,3-dithiane in order to prepare the
corresponding N-furanyl carbamate 16.
Loss of the Boc group occurs on heating at 130 °C or upon treatment of 16 with
Mg(ClO4)2. In an attempt to convert the
1,3-dithiane of the resulting NH-carbamate 17 to the corresponding carbonyl
group, the compound was treated with iodine
in a basic aqueous solution. Under these conditions, a rather unusual oxidative
rearrangement occurred to produce
a substituted 5-hydroxy-1H-pyrrol-2(5H)-one. Analogous oxidative rearrangements
were found to occur with structurally
related 2-amidofurans. The mechanism of the oxidative rearrangement is
comparable to the aza-Achmatowicz
reaction.
Keywords: Furanyl carbamate, oxidative rearrangement, aza-Achmatowicz, daphniphyllum, alkaloid