Method for the Selective Formation of Dimethyl Acetals in the Presence of Hydroxylamine

Abstract

An inexpensive and mild method for the formation of dimethyl acetals from the corresponding aldehydes is achieved using hydroxylamine and methanol under neutral conditions at room temperature. Notably, the reaction is selective for aldehydes in the presence of ketones, rendering this an example of a chemoselective acetalization. For saturated, sterically accessible aldehydes, catalytic amounts of hydroxylamine may be employed to attain the corresponding dimethyl acetal as the sole product in good to excellent yield. Unsaturated and hindered aldehydes required stoichiometric amounts of hydroxylamine but provided dimethyl acetals as the major product in typically excellent yield. In some cases, the corresponding oxime was also observed but may be separated from the acetal by flash column chromatography or distillation. The involvement of an intermediate oxime compound is postulated.

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GRAPHICAL ABSTRACT

Keywords:

• Acetal
• hydroxylamine
• oxime
• selective acetalization

ACKNOWLEDGMENT

The authors are grateful to Northern Arizona University for support of this project.