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

Flavones have been prepared by the 6-endo cyclization of o-alkynoylphenols, cyclization/deprotection of 2 '-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 MnO2. Thioflavones have been prepared by deprotection/6-endo cyclization of S-protected alkynones or by the addition of sulfur to 2 '-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 '-aminoalkynones or by the addition of amines to 2 '-haloalkynones and subsequent cyclization. Furthermore, the treatment of 2 '-aminoalkynones with triphenylphosphine afforded (Z)-azaaurones by 5-exo cyclization.

Automated summary

This article discusses the synthesis of flavones, aurones, thioflavones, thioaurones, and 2-phenyl-4-quinolones through various methods involving alkynoylphenols, alkynones, halophenols, benzylated alkynones, and amines.