Vilsmeier—Haack Reagent-Promoted Formyloxylation of α-Chloro-N-arylacetamides by Formamide.

In this study, a Vilsmeier–Haack reagent-promoted formyloxylation of α-chloro-N-arylacetamides by formamide was developed. The reaction successfully provided the desired α-formyloxy-N-arylacetamides 4 and 7a–n in moderate to excellent yields (70–96%) by use of 3.0 equivalents of PBr3 at 80–90 °C and was applicable to substrates bearing electron-donating or withdrawing groups at the aryl moiety. For α-chloro-N-(naphthalenyl)acetamide (8a), α-chloro-N-(quinolin-8-yl)acetamide (8b), and α-chloro-N-(thiazol-2-yl)acetamide (8c) possessing the α-chloro group, the reaction also provided the desired formyloxylated products 9a–c in 70–87% yields. A plausible mechanism was proposed through the activation of α-chloroacetamide by the Vilsmeier–Haack reagent to account for the new transformation.