Direct α-Iodination of Aryl Alkyl Ketones by Elemental Iodine Activated by 1-Chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane Bis(tetrafluoroborate)

Abstract

Selective introduction of an iodine atom at the α-carbonyl position in various aryl alkyl ketones was effectively achieved by reaction of target molecules with elemental iodine in the presence of N-F reagents. The best results were obtained by using 1-chloromethyl­-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetra­fluoroborate) (Selectfluor^{Τ Μ} F-TEDA-BF₄) as the iodination mediator and methanol as the solvent. Despite a strongly activated aromatic ring, iodomethyl derivatives were thus exclusively obtained from the corresponding hydroxy and methoxy substituted acetophenone derivatives, 3-acetylindole and 2-acetylbenzofuran, while the α-iodo derivative was the main product in the case of iodination of 1,5,6,7-tetrahydro-4H-indol-4-one and 6,7-dihydro-1-benzothiophene-4(5H)-one.

Key words

iodine - ketones - regioselectivity - fluorine

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