A series of novel indole derivatives bearing pyrimidine and cyclic imide scaffolds such as phthalic and maleic anhydrides has been designed and synthesized using both conventional and microwave irradiation (MW) methods under solvent free conditions. The title compounds have been developed by the reaction of 2-aminoo-4-hydroxy-6-(5,1-substituted-indol-3-yl) pyrimidine-5-carbonitrile with phthalic and maleic anhydrides individually using MW method. In addition, these target compounds were also synthesised under conventional heating method. A considerable increase in the reaction rate has been observed with better yields (90-92%) within 2-6 min using microwave irradiation in comparison to conventional thermal treatment.
A novel route was developed for synthesis of high potential 1H‐tetrazoles by using conventional method. Tetrazole scaffold is a promising pharmacophore fragment, frequently used in the development of various novel drugs. Here, the novel (Z)‐3‐(N‐alkyl‐indol‐3‐yl)‐2‐(1H‐tetrazole‐5‐yl)acrylates 5 (a–i) have been synthesized from (Z)‐ethyl‐3‐(1H‐indol‐3‐yl)2‐(1H‐tetrazol‐5‐yl)acrylates 4 (a–c) by using various alkylating agents such as Dimethyl Sulphate (DMS), Diethyl Sulphate (DES), and benzyl chloride; 4 (a–c) were synthesized from sodium azide in the presence of copper sulfate in dimethylformamide; 3 (a–c) have been prepared by Knoevenagel condensation of indole‐3‐carbaldehyde 1 (a–c) and ethylcyanoacetate 2 in the presence of L‐Proline as a catalyst at room temperature in ethanol for an hour. This is an efficient and clean click chemistry method that has various advantages such as easy workup, higher yields, shorter reaction times, and more economical.
A series of novel 1‐((1H‐1,2,3‐triazol‐4‐yl)methyl)‐2‐(1‐((1H‐1,2,3‐triazol‐4‐yl)methyl)‐5‐substituted‐1H‐indol‐3‐yl)‐6‐substituted‐1H‐benzo[d]imidazoles 5a–i have been prepared using click chemistry as an ideal strategy where [3 + 2] cycloaddition of azides with terminal alkynes has been developed as the target compounds. In route‐II, 5‐substituted‐1H‐indole‐3‐carbaldehydes 1a–c react with 5‐substituted orthophenylenediamine 8 to give desired products, that is, 6‐substituted‐2‐(5‐substituted‐1H‐indol‐3‐yl)‐1H‐benzo[d]imidazole 6a–i. Here, 6a–i react with 2 equiv of propargylbromide 7 to give novel 6‐substituted 2‐(5‐substituted‐1‐(prop‐2‐yn‐1‐yl)‐1H‐indol‐3‐yl)‐1‐(prop‐2‐yn‐1‐yl)‐1H‐benzo[d]imidazole 4a–i. 4a–i were reacted with 2 equiv of NaN3 in t‐butanol/water (1:2) and add catalytic amount of CuSO4.5H2O. Stir the reaction mixture at room temperature to get the target products 5a–i. Here, obtained products contain four rings, that is, one indole, two triazoles, and one benzimidazole. The main advantages of this method are short reaction times, easy workup, higher yields (88–92%), and no by‐products formation.
A series of novel indole and pyrimidine scaffolds bearing 1,2,3‐triazoles have been designed and synthesized using click chemistry reaction conditions. Target compounds 9a‐j were synthesized in the multi‐step process. In the first step 5‐substituted‐1‐methyl‐1H‐indole‐3‐carbaldehyde 2a‐b reacted with ethyl cyanoacetate 3 and guanidine hydrochloride 4 in presence of L‐Proline in ethanol undergoes cyclisation to form 5a‐b. Further, 5a‐b condensed with various benzaldehydes to form Schiff's base 6a‐f, which further proporgylated with propargyl bromide to form 7a‐f. Finally, 7a‐f was subjected to click‐chemistry with various azides in the presence of CuSO4.5H2O + sodium ascorbate mixture in Dimethylformamide at room temperature to obtain 2 + 3 cycloaddition products 9a‐j in high yield. All these synthetic methods are mostly green and inexpensive with excellent yields.
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