A review of the syntheses of (thio)flavones, 4‐quinolones, (thio)aurones, and azaaurones from 2′‐substituted alkynones

Abstract

Flavones have been prepared by the 6-endo cyclization of o-alkynoylphenols, cyclization/deprotection of 2 0 -protected alkynones, or carbonylative coupling of 2-halophenols with arylacetylenes and subsequent cyclization. (Z)-Aurones have been prepared by the 5-exo cyclization of o-alkynoylphenols or oxidation of (Z)-benzylidenebenzofuran-3-ols with MnO 2 . Thioflavones have been prepared by deprotection/6-endo cyclization of S-protected alkynones or by the addition of sulfur to 2 0 -halo(methoxy)alkynones and subsequent cyclization. Deprotection and 5-exo cyclization of S-benzylated alkynones using HCOOH afforded (Z)-thioaurones. 2-Phenyl-4-quinolones have been prepared by the 6-endo cyclization of 2 0 -aminoalkynones or by the addition of amines to 2 0haloalkynones and subsequent cyclization. Furthermore, the treatment of 2 0aminoalkynones with triphenylphosphine afforded (Z)-azaaurones by 5-exo cyclization.