Selectfluor-Mediated Tandem Cyclization of Enaminones for the Synthesis of 3-Fluorochromones

Abstract

An efficient synthesis of various 3-fluorochromones (3-fluoro-4H-chromene-4-ones) from enamino ketones by using Selectfluor is described. The key step in the synthesis involves tandem fluorination and cyclization to form 3-fluorochromones in good yields. The significant features of this method include simple operational procedures, a high purity of the product, and excellent regioselectivity.

Selectfluor-triggered fluorination/cyclization of o-hydroxyarylenaminones: A facile access to 3-fluoro-chromones

“…As our ongoing interest in enaminone chemistry, [73][74][75][76][77][78][79][80][81][82] herein, we report a fast and efficient Selectfluor-triggered fluorination/cyclization reaction of o-hydroxyarylenaminones for the construction of 3-fluoro-chromones promoted by potassium carbonate (Scheme 1(c)). Interestingly, this reaction is mechanistically different compared to the previously reported methods 71,72 where 2-(dimethylamino)-3,3difluorochroman-4-one.…”

“…In 2017, the groups of Zhao 69 and Xu 70 developed a Selectfluortriggered tandem cyclization of o-hydroxyarylenaminones to obtain 3,3-difluorinated 2-amino-substituted chromanones, respectively (Scheme 1(b)). In addition, the groups of Kandula 71 and Zhao 72 also reported a Selectfluor-triggered tandem cyclization strategy for constructing 3-fluoro-chromones via direct elimination of 3,3-difluorinated 2-amino chromanones at room temperature in a short time ago. As our ongoing interest in enaminone chemistry, [73][74][75][76][77][78][79][80][81][82] herein, we report a fast and efficient Selectfluor-triggered fluorination/cyclization reaction of o-hydroxyarylenaminones for the construction of 3-fluoro-chromones promoted by potassium carbonate (Scheme 1(c)).…”

Recent advances in the synthesis of 4H-chromen-4-ones (2012 − 2021)

“…Various 3-iodo-4H-chromen-4-ones arise from one-pot ring-closure and iodination sequence via addition of molecular iodine to o-hydroxyaryl enaminones employing methanol, [242][243][244][245][246][247] chloroform, 248,249 pyridine and chloroform, [250][251][252][253][254] pyridine and dichloromethane 47,255 as solvents, at room temperature. Examples of 3-fluoro-4H-chromen-4-ones were synthesized through the monofluorination of o-hydroxyaryl enaminones with Selectfluor ® as fluorine source in 1,2-DCE at room temperature, 256 in the presence of sodium acetate and butylated hydroxytoluene (BHT)…”

Langlois Reagent Mediated Tandem Cyclization of o-Hydroxyaryl Enaminones for the Synthesis of 3-(Trifluoromethyl)chromones

“…We recently developed a novel and efficient Selectfluor-mediated reaction for the synthesis of 3-fluorochromones from readily available o -hydroxyacetophenones. 26 We surmised that the Langlois reagent might be used analogously for a tandem cyclization and trifluoromethylation of a suitably substituted enaminones 4 to give the corresponding 3-(trifluoromethyl)chromones 5 (Scheme 2 ). Here, we report the synthesis of 3-(trifluoromethyl)chromones by using the Langolis reagent in DMSO containing a catalytic amount of Cu(OAc) 2 , with TBHP as an oxidant.…”