Facile and regioselective synthesis of functionalized benzenes via cascade reactions of 1,2-allenic ketones with 4-sulfonyl crotonates.

An efficient and regioselective synthesis of functionalized benzenes via the cascade reactions of 1,2-allenic ketones with 4-sulfonyl crotonates under mild reaction conditions has been established. Mechanistically, the formation of the title compounds involves a cascade procedure consisting of an intermolecular regioselective Michael addition followed by an intramolecular condensation and aromatization. Compared with those of α,β-unsaturated aldehydes/ketones, the reactions of 1,2-allenic ketones with 4-sulfonyl crotonates demonstrated contrary regio-selectivity and distinct reaction conditions. Moreover, the functionalized benzene products obtained herein were found to be ready intermediates for the synthesis of fluorenone and anthracenone derivatives. [ABSTRACT FROM AUTHOR]