Prof. Maulide: Gold-Catalyzed Synthesis of Furans and Furanones from Sulfonium Ylides

Angew. Chem. Int. Ed. 2012,51, 8886-8890 and Angew. Chem. 2012, 124, 9016-9020

Introduction:

Polysubstituted furan derivatives are fundamental building blocks in organic synthesis and find wide representation among natural products, agrochemicals, and pharmaceuticals.^[1] Herein, a simple and flexible gold-catalyzed synthesis of densely functionalized 3-carboxyfuran derivatives is reported. The starting materials, stabilized sulfonium ylides, are prepared by ylide transfer^[2] employing Martin’s Sulfurane^[3].

Scope:

A variety of bicyclofurans could be readily prepared by simply stirring appropriate sulfonium ylide precursors in the presence of a gold catalyst at room temperature (Scheme 1).

2- Intermolecular Synthesis of furans:

Intermolecular furan synthesis by this procedure proved particularly sensitive to the substitution pattern of both the sulfonium ylide and the alkyne partner (Scheme 2). In the event, malonate-derived sulfonium ylides provided alkoxyfurans in reasonable efficiency.

3- Synthesis of -lactones from sulfonium ylides and alkynes :

Under the influence of Echavarren’s catalyst,^[4] the use of allyloxyesters in conjunction with arylacetylenes afforded C-allylated 2-furanones carrying a quaternary center, along with the expected furan product (Scheme 3).

Conclusion:

A gold-catalyzed synthesis of heterocycles was developed from doubly-stabilized sulfonium ylides. This transformation is amenable to a reactivity switch triggered by modification of the electron-withdrawing moieties of the ylide partner, delivering either furans or furanones bearing a quaternary center as products.