Thallium(III) p‐tosylate‐mediated oxidative [1,2] rearrangement of 2‐naphthyl and 2‐heteroarylchromanones

Abstract

A practical and effective approach towards the synthesis of 3-heteroaryl-4Hchromen-4-ones by the oxidative [1,2] rearrangement of the respective 2-heteroaryl chroman-4-ones using thallium(III) p-tosylate is presented. The oxidative rearrangement of αand β-naphthyl and thiophene substituents behaves like aryl groups; However, pyridyl substituents gave only dehydrogenated products.

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

“…In addition, the oxidation of the 2-pyridinylchroman-4-ones was also observed when using thallium(III) p-tosylate (TTS) in refluxing acetonitrile. 228 2-{Diaryl[(trimethylsilyl)oxy]methyl}-4H-chroman-4-ones suffered dehydrosiloxylation promoted by a catalytic amount of PTSA in refluxing xylene to afford the corresponding 2-diarylmethyl-4H-chromen-4ones. These products could also be prepared starting from the same precursors, which underwent desilylation by treatment with hydrochloric acid in 1,4-dioxane to obtain the alcohol intermediates and subsequent dehydration, mediated by a catalytic amount of PTSA in refluxing toluene.…”

“…346 A more selective protocol was reported by Kurapati et al for the oxidative rearrangement of various 2-(hetero)aryl-4H-chroman-4-ones (naphthalen-1-yl, naphthalen-2-yl, thiophen-1-yl, thiophen-2-yl), carried out in the presence of TTS in refluxing acetonitrile to produce the corresponding 3-(hetero)aryl-4H-chromen-4-ones. 228…”