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The use of the coinage metals copper, silver, and gold enables an efficient and stereoselective assembly of bioactive heterocycles via allenic intermediates. Whereas copper is mediating or catalyzing the synthesis of functionalized allenes by SN2′-substitution or SN2′-reduction, silver and gold are the catalysts of choice for subsequent 5- or 6-endo-cyclizations. Overall, this sequence proceeds with efficient center-to-axis-to-center chirality transfer. Recent advances of this combined coinage metal catalysis include the synthesis and transformation of substrates containing two adjacent allenic π-systems or heteroatoms, the development of recyclable gold catalysts, and the combination of two catalytic processes in tandem or one-pot reactions.

The use of the coinage metals copper, silver, and gold enables an efficient and stereoselective assembly of bioactive heterocycles via allenic intermediates. Whereas copper is mediating or catalyzing the synthesis of functionalized allenes by SN2 0 -substitution or SN2 0 -reduction, silver and gold are the catalysts of choice for subsequent 5- or 6-endo-cyclizations. Overall, this sequence proceeds with efficient center-to-axis-tocenter chirality transfer. Recent advances of this combined coinage metal catalysis include the synthesis and transformation of substrates containing two adjacent allenic p-systems or heteroatoms, the development of recyclable gold catalysts, and the combination of two catalytic processes in tandem or one-pot reactions.

A stereoselective synthesis of conjugated bis(α-hydroxyallenes) by copper-mediated SN2′-substitution is described. Their silver- or gold-catalyzed cycloisomerization affords highly functionalized 2-allenyl-substituted 2,5-dihydrofurans and bis(2,5-dihydrofurans) under axis-to-center chirality transfer.

Nucleophilic heterocyclic carbene (NHC)-catalyzed annulation of enals proceeds with variety of 1,2-dicarbonyl compounds, leading to the formation of 4,4,5-trisubstituted γ-butyrolactones.

The zwitterion formed by the reaction of dimethoxycarbene and DMAD adds efficiently to one of the carbonyl groups of 1,2-dicarbonyl compounds and anhydrides to generate dihydrofurans and spirodihydrofurans in good yields. In many cases, the carbene inserts into the C-C bond of the dione to yield masked vicinal tricarbonyl systems.

A simple protocol for the efficient synthesis of 3(2H)-furanones by cycloisomerization of allenic hydroxyketones is described. This transformation is achieved in water and in the absence of any expensive metal catalysts.

[reaction: see text]. Nucleophilic heterocyclic carbene (NHC) catalyzed annulation of enals and cyclic 1,2-dicarbonyl compounds, opening a route to gamma-spirolactones, has been observed for the first time. The strategy works well with isatins, leading to spiroannulated oxindole derivatives. It is conceivable that the spiroannulation protocol reported herein will be applicable to the synthesis of important natural products that are endowed with a spiro gamma-butyrolactone motif, especially oxindoles and norsesquiterpenoids.

Treatment of allenic hydroxyketones with aqueous NaOH provides a new and simple approach to 3-furanones.

The use of the coinage metals copper, silver, and gold enables an efficient and stereoselective assembly of bioactive heterocycles via allenic intermediates. Whereas copper is mediating or catalyzing the synthesis of functionalized allenes by SN2 0 -substitution or SN2 0 -reduction, silver and gold are the catalysts of choice for subsequent 5- or 6-endo-cyclizations. Overall, this sequence proceeds with efficient center-to-axis-tocenter chirality transfer. Recent advances of this combined coinage metal catalysis include the synthesis and transformation of substrates containing two adjacent allenic p-systems or heteroatoms, the development of recyclable gold catalysts, and the combination of two catalytic processes in tandem or one-pot reactions.

A stereoselective synthesis of conjugated bis(α-hydroxyallenes) by copper-mediated SN2′-substitution is described. Their silver- or gold-catalyzed cycloisomerization affords highly functionalized 2-allenyl-substituted 2,5-dihydrofurans and bis(2,5-dihydrofurans) under axis-to-center chirality transfer.

Nucleophilic heterocyclic carbene (NHC)-catalyzed annulation of enals proceeds with variety of 1,2-dicarbonyl compounds, leading to the formation of 4,4,5-trisubstituted γ-butyrolactones.

A novel protocol for the annulation of tropone to enals involving nucleophilic heterocyclic carbene (NHC) catalyzed homoenolate formation has been developed. Interestingly, the reaction led to bicyclic delta-lactones instead of the expected gamma-spirolactones, presumably by the uncommon [8 + 3] annulation pathway. The strategy works well with a variety of enals.

Nucleophilic heterocyclic carbene-catalyzed cyclopentannulation of enals and chalcones via homoenolate has been observed for the first time. Serendipitously, the reaction lead to a very efficient synthesis of 3,4-trans-disubstituted-1-aryl cyclopentenes instead of the expected cyclopentanones. The strategy works well with thienylidene tetralone also, leading to the tricyclic cyclopentene derivative.

The molecule of the title compound, C20H34O4, is centrosymmetric. In the crystal structure, a network of O—H...O hydrogen bonds result in each molecule being linked to four neighbouring molecules and a two-dimensional net is formed.