Synthesis of Formate Esters and Formamides Using an Au/TiO2-Catalyzed Aerobic Oxidative Coupling of Paraformaldehyde

Abstract

A simple method for the synthesis of formate esters and formamides is presented based on the Au/TiO2-catalyzed aerobic oxidative coupling between alcohols or amines and formaldehyde. The suitable form of formaldehyde is paraformaldehyde, as cyclic trimeric 1,3,5-trioxane is inactive. The reaction proceeds via the formation of an intermediate hemiacetal or hemiaminal, respectively, followed by the Au nanoparticle-catalyzed aerobic oxidation of the intermediate. Typically, the oxidative coupling between formaldehyde (2 equiv) and amines occurs quantitatively at room temperature within 4 h, and there is no need to add a base as in analogous coupling reactions. The oxidative coupling between formaldehyde (typically 3 equiv) and alcohols is unprecedented and occurs more slowly, yet in good to excellent yields and selectivity. Minor side-products (2–12%) from the acetalization of formaldehyde by the alcohol are also formed. The catalyst is recyclable and can be reused after a simple filtration in five consecutive runs with a small loss of activity.

Cu-Catalysed sustainable synthesis of formamide with glycerol derivatives as a carbonyl source via a radical-relay mechanism

“…As one of the important nitrogen-containing chemicals, formamides have widespread applications in organic synthesis and industrial production, and various methods have been developed for their production. [16][17][18][19][20][21][22][23][24][25][26][27][28] N-Formylation of amines with formylation reagents is a widely used method, and the common formylation reagents include CO, 27 CO 2 , 17,18,[29][30][31][32][33][34] formic acid, 23,27,35 formaldehyde [36][37][38][39][40][41][42][43] and methanol. [43][44][45][46] Although some excellent results have been obtained, obvious problems such as high toxicity and cost, requirement of harsh equipment and reaction conditions, poor product selectivity and so on have limited their large-scale application.…”

Metal-Free N-Formylation of Amines Using Carbohydrates as C1 Synthon via C–C Bond Cleavage

“…In this regard, in order to avoid the conventional toxic reagents as used in the past, various formylation methods using different C1 synthons have been developed and reported in the literature. A list of reagents and solvents those act as C1 synthons include carbon monoxide (CO), 51,52 carbon dioxide (CO 2 ), [53][54][55][56][57][58][59] paraformaldehyde, 60,61 trialkyl orthoformate [62][63][64] methanol (MeOH), [65][66][67][68][69][70] dimethylformamide (DMF), [71][72][73][74][75][76] ethers, [77][78][79] glycolaldehyde, 80 glyceraldehyde, 81 glycolic acid, 81 1,3-dihydroxyacetone 81 and these incorporate CHO, CN, CH, CH 2 , and CH 3 in organic molecules. Among above mentioned reagents DMF, and MeOH are the most significant due to their cost-effectiveness, low toxicity, and easy availability.…”

Novel and Efficient Synthesis of Phenethyl Formate via Enzymatic Esterification of Formic Acid

“…The log P values of cyclohexane, n-hexane, heptane, and isooctane are 3.4, 4.0, 4.27, and 4.6, respectively, which indicate their strong hydrophobicity. Lipase activity can be maintained in these solvents, but water (as a byproduct) is accumulated and concentrated at the enzyme's active sites, leading to ester hydrolysis and adversely affecting the conversion [10,18,42]. In addition, a highly hydrophobic solvent is not suitable for conversion owing to the insolubility of formic acid in these solvents [52].…”

“…In this context, the synthesis of formate esters from formic acid has been extensively studied [4,5]. Formate esters are notably more expensive than formic acid (approximately 50 to 100 times greater value addition) [6], and thus, various methods have been developed for their synthesis (Table 1) [4,5,[7][8][9][10]. Esters, such as formate ester, are generally synthesized by the esterification of carboxylic acids with alcohols.…”