Bougault reaction

What is Bougault reaction?

The Bougault reaction, also referred to as the Bougault cyclization, was initially discovered by Bougault in 1915. This reaction involves the condensation of β-arylpropionic acid ester with diethyl oxalate, followed by the cyclization of the resulting glyoxylate ester using sulfuric acid H2SO4 to produce indene derivatives.

Bougault reaction - general reaction scheme - Bougault cyclization
Bougault reaction

However, when using sulfuric acid H2SO4, hydrolytic cleavage, ester exchange, or extensive sulfonation may occur, so phosphoric acid H3PO4 may be a better reagent for cyclization. Furthermore, this reaction has been applied to synthesize indene, dihydronaphthalene and phenanthrene derivatives.

References

Bougault, J., Compt. Rend., 1915, 159, 745

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