Aqueous Formaldehyde

Introduction

Between the different sources of formaldehyde as a C ₁ synthon in organic synthesis, the use of a commercial aqueous solution is the most convenient. It avoids the tedious and harmful procedures to generate the formaldehyde monomer from formaldehyde oligomers such as paraformaldehyde and trioxane. Besides being an inexpensive and commercially available reagent, aqueous formaldehyde is a good electrophile and has been used in various organic transformations, such as N-methylation and α-methylation of carbonyl compounds, aminomethylation, hydroxymethylation, Prins reaction and Wittig-type methylenation. A recently published Spotlight on formaldehyde [¹] has mentioned only one case of use of the aqueous solution, the synthesis of propargylamines. [²] In this review a more complete extension of the use of aqueous formaldehyde is presented. The usual process for producing formaldehyde is by oxidative dehydrogenation of methanol using iron metal or its mixtures with molybdenum. [³]

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