N2 - Green approaches for efficient synthesis of quinazoline- and pyrimidine-2-amine derivatives were established based on the one-pot and three-component condensation of guanidine carbonate, cyclic ketones and aldehydes. These approaches involve the evaluation of the activity of several acidic ionic liquids (ILs) as organocatalysts under solvent-free medium in the microwave and as solvents and catalysts in the ultrasound irradiations. Reactions were evaluated for a number of substituted aldehydes and cyclic ketones on the basis of variation of parameters including type and amount of ILs, reaction temperature and time. Compared to the ultrasound method, the solvent-free procedure in the microwave was found to be more efficient in terms of both chemical yield and reaction time. Catalyst recyclability, simplicity, and time-saving aspects of the reaction suggests that these methods present real alternatives to conventional reaction protocols.
The ureidomalonates did not react with or -alkylisothioureas (see ). The pyrimidines obtained from reaction of with guanidine were greatly influenced by the stoichiometry of the reaction, with a fourfold excess of guanidine leading almost exclusively to (2) (eq 6).A simple, one-pot synthesis of 2-substituted 5-vinylpyrimidines involves cyclization of 1-vinylpiperidylacrolein (4) with amidines, including guanidine and 1,1-dimethylguanidine (eq 7). Cyclization of acrylates and methacrylates with guanidine in -butyl or isopropyl alcohol at room temperature provides a high-yield synthesis of the rather inaccessible dihydropyrimidines (eq 8). With guanidine and methylguanidine the reaction proceeds in a few hours, whereas both 1,1- and 1,2-dimethylguanidine require 48 h and 1,2,3-trimethylguanidine is unreactive.
Substituted guanidine synthesis essay - Salles …
[15N]Guanidine has been prepared and used to prove the mechanism for cyclization of heterocyclic -aminonitriles to fused 2,4-diaminopyrimidines.A general synthesis of 2-amino- and 2-substituted amino-1,3,5-triazines involves cyclization of the appropriate guanidine sulfate with , a precursor to -formylformamidine, the actual species involved in the reaction (eq 9). Best results were obtained using a 1:2 ratio of guanidine to tris(formamido)methane.