Highly Selective Phosgene-Free Carbamoylation of Aniline by Dimethyl Carbonate under Continuous-Flow Conditions

Abstract

Over the last 20 years organic carbamates have found numerous applications in pesticides, fungicides, herbicides, dyes, pharmaceuticals, cosmetics, and as protecting groups and intermediates for polyurethane synthesis. Recently, in order to avoid phosgene-based synthesis of carbamates, many environmentally benign and alternative pathways have been investigated. However, few examples of carbamoylation of aniline in continuous-flow apparatus have been reported. In this work, we report a high-yielding, dimethyl carbonate (DMC)-mediated carbamoylation of aniline in a fixed-bed continuously fed reactor employing basic zinc carbonate as catalyst. Several variables of the system have been investigated (i.e. molar ratio of reagents , flow rate, and reaction temperature) to optimize the operating conditions of the system.

Zr-MOF-808@MCM-41 catalyzed phosgene-free synthesis of polyurethane precursors

“…10 This latter system has also allowed to carry out the carbamoylation reaction of aniline in a fixed-bed continuously fed reactor. 28 A nanostarchfuntionalized ionic liquid containing a cobalt chelate anion have been successfully applied in the carbamoylation reaction of anilines and aliphatic amines by the reaction with DMC. 29 Curiously, all of the above heterogeneous catalysts have been exclusively tested in the carbamoylation reaction of aniline with DMC.…”

The neighbouring effect of isosorbide and its epimers in their reactions with dimethyl carbonate

“…Dimethyl carbonate (DMC), nowadays produced by a clean and halogen-free process [7][8][9], is a well-known environmentally benign substitute of phosgene in carboxymethylation reactions (via B Ac 2 mechanism) and DMS or methyl halides in methylation reactions (via B Al 2 mechanism). DMC has also numerous applications as nontoxic solvent and reagent [10][11][12][13][14][15][16][17][18][19][20]. In general DMC, as a methylating agent requires temperatures higher than 150°C in the presence of a base and an appropriate nucleophile [21].…”

5-Membered cyclic ethers via phenonium ion mediated cyclization through carbonate chemistry

“…In fact, DMC acts as methoxycarbonylation agent with harder nucleophiles via a B Ac 2 mechanism at reflux temperature (T = 90 °C) and as methylating agent with softer nucleophiles via a B Al 2 mechanism, at higher temperature (T > 150 °C) [15][16][17][18][19][20][21][22][23] (Fig. 1).…”