A Synthesis of Acetamidines

Abstract

The condensation of primary amine with N,N-dimethylacetamide dimethyl acetal yields a mixture of acetamidine and imidate ester. The product distribution in this reaction depends on the temperature, solvent, and structure of the primary amine. It is possible to suppress the formation of imidate ester by performing the reaction in the presence of excess dimethyl amine, yielding acetamidine as the exclusive product. For acetamidines that cannot be purified either by crystallization or distillation, this new method is necessary for the generation of pure acetamidines in good yields.

Strategy for Synthesizing Novel Acetamidines as CO2-Triggered Switchable Surfactants via Acetimidates

“…We prepared N'-dodecyl-N,N-dimethylacetamidine (1b) in experiments 1 and 2, as shown in Table 1, according to methods reported in Refs. [21,28]. We recorded the proton nuclear magnetic resonance ( 1 H NMR) and carbon-13 nuclear magnetic resonance ( 13 C NMR) of the reaction products on a Varian Inova spectrometer (Varian, America, 500 MHz), for which all the chemical shift values refer to CDCl 3 (δ( 1 H), 7.26 ppm; δ( 13 C), 77.16 ppm).…”

“…Experimental Process for the Results Shown in Fig. 2 First, we prepared a certain amount of purified N'-dodecyl-N,N-dimethylacetamidine (1b) using the method developed by Jessop et al [21]. We added about 0.012 mol of N,N-dimethylacetamide dimethyl acetal (1.72 g) and 76.4 mmol of Me 2 NH (38 mL, 2 mol/L solution in tetrahydrofuran) into a three-neck round-bottom brown flask and stirred the mixture (100 r/min) at 25 °C.…”

“…As such, compounds containing an amidine head [21,22] are attracting more attention due to their mild basicity and superior stability. In addition, the exceptional demulsifying ability of amidines in their neutral form is an unexpected advantage.…”

“…Of these synthetic methods, the Scoggins procedure involving primary amines and N,N-dimethylacetamide dimethyl acetal can synthesize long-chain aliphatic amidines and aromatic amidines with a high yield of 90% accompanied by the formation of a small amount of imidates as a by-product [27,28]. This is particularly attractive since an encouraging acetamidines yield of 99% was achieved by Jessop et al [21] when they added an excess amount of dimethylamine to the reaction system. However, the types of amidines used in this synthesis method have been fairly limited thus far, due to the limitation of commercially available reactants.…”

“…However, the types of amidines used in this synthesis method have been fairly limited thus far, due to the limitation of commercially available reactants. The structure of amidines generated by this method differed from those in the hydrophobic tail group, which are mainly long-chain alkyl or ethoxylated groups, or both [16,21], and the hydrophilic head is bonded only with the dimethyl group.…”