K2CO3 catalyzed solvent-free synthesis of molecular tweezers containing chiral unsymmetrical urea unit under microwave irradiation

Microwave-Assisted Synthesis of Bidentate Chiral Unsymmetrical Urea Derivatives of P-tert-butylcalix[4]Arene and their Anion Recognition Properties

“…24 Although compound 4 was prepared by conventional heating by refluxing acid 3 for 4 h with SOCl 2 /benzene, 24 we found that the reaction time could be shortened to 7 min if microwave irradiation replaced conventional heating. The preparation of unsymmetrical ureasubstituted chiral amino alcohols 5a-d have been described previously in Chinese, 23 so their syntheses are repeated in the Experimental for English readers.…”

Synthesis of Novel Triazole Derivatives of Methyl 3-Oxocholanate Using Microwave Irradiation

“…It possesses useful attributes, such as ease of manipulation, enhanced reaction rates, clean reaction outcomes and high yields. [18][19][20][21][22][23] To the best of our knowledge, no work has been published on the synthesis and physicochemical properties of triazole derivatives obtained from methyl 3-oxocholanate. In view of this, we now report a simple, efficient and rapid synthetic method for preparing steroidal triazoles based on methyl 3-oxocholanate by condensation of the steroidal ketone with the 4-amino-3-substituted-1H-1,2,4-triazole-5-thione under microwave irradiation.…”

Solvent-free synthesis of novel chiral unsymmetrical urea molecular tweezers under microwave irradiation

“…Moreover, the technique of microwave irradiation in solvent-free conditions has become a valuable tool in organic synthesis because of the advantages such as reducing reaction time, getting cleaner reactions, improving yields, simplifying work-up and designing energy-saving protocols. [12][13][14] In continuation of our ongoing programme to synthesise molecular tweezers using microwave activation, [15][16][17][18][19][20] we now report a facile and rapid synthetic method in the solid state using microwaves to synthesise chiral unsymmetrical urea-type molecular tweezers. The molecular tweezers shown in Scheme 1 have a cavity in which four NH groups direct towards the centre of the cavity, and the NH group could form hydrogen bonds with substrates in the process of molecular recognition.…”