Recent Developments on the Carbamation of Amines

Abstract

Organic carbamates represent an important class of compounds showing various interesting properties. They find wide utility in various areas as pharmaceuticals, agrochemicals (pesticides, herbicides, insecticides, fungicides etc.), intermediates in organic synthesis, protection of amino group in peptide chemistry, and as linker in combinatorial chemistry etc. Classical synthesis of carbamates involves use of harmful reagents such as phosgene, its derivatives and carbon monoxide. Recently, various kinds of synthetic methods have been developed for the synthesis of organic carbamates. In the present review, I would like to highlight the recent developments on the synthesis of organic carbamates using variety of reagents.

Unprecedented “In Water” Imidazole Carbonylation: Paradigm Shift for Preparation of Urea and Carbamate

“…Urea and carbamate are important functional groups found in pharmaceutical candidates, agrochemicals, and material science . Although a number of methodologies, such as oxidative carbonylation of amines and dialkyl based exchange processes, have been developed recently for the synthesis of ureas and carbamates which are environmentaly more benign, a standard method for rapid library generation of urea and carbamate involves use of a transfer reagent such as phosgene, triphosgene, 1,1′-carbonylimidazole, carbonylimidazolium salt, chloroformates, or some carbamoyl cation equivalent such as isocyanates or carbamoylchlorides. There are significant drawbacks associated with many of these reagents.…”

Reaction of Amino-Terminated PAMAM Dendrimers with Carbon Dioxide in Aqueous and Methanol Solutions

“…The NMR spectra of PAMAM dendrimers have been investigated before and we followed the findings of previous work [9,10] to assign the observed 1 H NMR resonances in our experiments. The corresponding NMR spectra recorded in D 2 O solution are shown in the Supplementary Materials.…”

“…Carbon dioxide reacts with amines to form carbamic acid [1]. In the presence of excess amine, the acid becomes deprotonated, leading to a mixture of carbamates and protonated amines that may undergo electrostatic interactions, whose strength may depend on reactant concentrations and solvent nature, among other factors (Scheme 1).…”

Continuous Synthesis of Carbamates from CO2 and Amines

“…19,20 The industrial synthesis of organic carbamates relied on reacting alkyl isocyanates with alcohols. 21 Isocyanates are considered highly toxic reagents, as evidenced by the disastrous chemical accidents in the past; 22 thus, they are often formed in situ to avoid safety hazards associated with handling large amounts of isocyanates. Other strategies react alkyl chloroformates with amines, thus generating at least stoichiometric amounts of HCl as a waste byproduct.…”