Synthesis of thioflavones
A one-pot Friedel-Crafts acylation of alkynes with suitably substituted benzoyl chlorides provides chromenones and thiochromenones. The ready availability of both starting materials, alkynes and benzoyl chlorides, coupled with the experimental simplicity makes the current synthetic method to (thio)chromenones fast, efficient, and practical.
H. Y. Kim, E. Song, K. Oh, Org. Lett., 2017, 19, 312-315.
4-Quinolones and 4H-thiochromen-4-ones are readily synthesized in a tandem one-pot manner from (Z)-β-chlorovinyl ketones in in good to excellent yields. An intermolecular nucleophilic addition of amines or sodium hydrogen sulfide to (Z)-β-chlorovinyl ketones is followed by elimination of a chlorine anion to give a Z-enamine or thioenol intermediate, which gives the desired products through intramolecular SNAr reaction.
D. Wang, P. Sun, P. Jia, J. Peng, Y. Yue, C. Chen, Synthesis, 2017, 49, 4309-4320.
A rhodium-catalyzed carbonylative annulation methodology with nonactivated aromatic sulfides and terminal alkynes as the substrates provides thiochromenones effectively via [3 + 2+1]-type annulation.
F. Zhu, X.-F. Wu, J. Org. Chem., 2018, 83, 13612-13617.
A mild ICl-induced cyclization of heteroatom-substituted alkynones provides a simple, highly efficient approach to various 3-iodochromones, iodothiochromenones, iodoquinolinones and analogues in good to excellent yields. Subsequent palladium-catalyzed transformations afford a rapid increase in molecular complexity.
C. Zhou, A. V. Dubrovsky, R. C. Larock, J. Org. Chem., 2006, 71, 1626-1632.