Abstract
2,2-Disubstituted 1,3-cyclopentanediones are versatile building blocks for synthesizing
complex natural products with bicyclic structures including cyclopentane rings. The
reported method for the synthesis of these compounds involves the semi-pinacol rearrangement
of a Mukaiyama aldol adduct prepared from a ketone/ketal and 1,2-bis(trimethylsilyloxy)cyclobutene.
However, the adoption of α-oxy-functionalized ketones/ketals is quite difficult, as
demonstrated by our experiments. To overcome this limitation of the method, 2-acylfuran
derivatives were used as the reactants to synthesize 2,2-disubstituted 1,3-cyclopentanediones.
Furthermore, two reaction conditions, that is, the use of 1.4 equivalents of a boron
trifluoride-diethyl ether complex or 0.4 and 0.2 equivalent of trimethylsilyl triflate
and methoxytrimethylsilane, respectively, were established for the conversion of 2-acylfurans
into the corresponding 1,3-cyclopentanediones in acceptable yields. The transformations
of the furan rings in the obtained products were also investigated.
Key words
1,3-cyclopentanedione - 1,2-bis(trimethylsilyloxy)cyclobutene - 2-acylfuran - semi-pinacol
rearrangement - trimethylsilyl triflate
