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Efficient Catalytic Activity of Transition Metal Ions in Vilsmeier–Haack Reactions with Acetophenones

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Correspondence to: K. C. Rajanna; e-mail: kcrajannaou@yahoo.com.

ABSTRACT

Vilsmeier–Haack (VH) formylation reactions with acetophenones are sluggish in acetonitrile medium even at elevated temperatures. However, millimolar concentrations of transition metal ions such as Cu(II), Ni(II), Co(II), and Cd(II) were found to exhibit efficient catalytic activity in Vilsmeier–Haack Reactions with acetophenones. Reactions are accelerated remarkably in the presence of transition metal ions. The VH reactions followed second order kinetics and afforded acetyl derivatives under kinetic conditions also irrespective of the nature of oxychloride (POCl3 or SOCl2) used for the preparation of VH reagent along with DMF. On the basis of UV–vis spectroscopic studies and kinetic observations, participation of a ternary precursor [M(II) S (VHR)] in the rate-limiting step has been proposed to explain the mechanism of the metal ion–catalyzed VH reaction.

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