New, Efficient Synthesis of α-Chloroketones Using SiCl₄/Urea–Hydrogen Peroxide or SiCl₄/Iodosylbenzene Reagent Systems

Abstract

Alkyl aryl ketones on treatment with SiCl₄/urea–hydrogen peroxide (UHP) or SiCl₄/iodosylbenzne reagent systems afforded α-chloroketones in excllent yields, while ketones with higher enol content provide exclusively α,α-dichloroketones under exceedingly mild conditions. The reaction proceeds via the initial formation of silyl enol ethers. A polarized chlorine intermediate that resulted from the coordination of SiCl₄ with the in situ formed trichlorosilyl hypochlorite Cl₃SiOCl is thought to be the active chlorinating agent.

Keywords:

• α-Chloroketones
• iodosylbenzene
• silyl peroxides
• tetrachlorosilane (TCS)
• urea–hydrogen peroxide (UHP)

Notes

^a Yields and reaction time using TCS/UHP.

^b Yields and reaction time using TCS/PhIO.