Synthesis And Cytotoxic Activity Against Cancer Cells Of Pyrazolo[1, 5-α]Quinoline And Pyrazolo[1,5-α]indole Derivatives

It was reported by Hajime Katayama that pyrazolo[1,5-a]indole derivatives have strong cytotoxic activity against cancer cells. According to analysis of the structure-activity relationship of these compounds, we figured out a similar structure, pyrazolo[1,5-a]quinoline derivatives. Recent reports of Cu(I)-catalyzed intermolecular C-N coupling reactions and tandem reactions enticed us to search for a new method of copper(I)-catalyzed tandem cyclization/condensation reaction to synthesize pyrazolo[1,5-a]quinoline and pyrazolo[1,5-a]indole structures.Substituted 2-bromophenylpropanoic acids were converted to 1,3-diketones step by step. We explored the effects of metals, ligands, bases and solvents on the typical reaction, and found out that the use of CuI as metal source, 1,10-phenanthroline as ligand, K2CO3 as base, anhydrous 1,4-dioxane as solvent, is the most optimal condition for the synthesis of not only pyrazolo[1,5-a]quinolines but also pyrazolo[1,5-a]indoles.Based on the above study, eighteen 4,5-dihydropyrazolo[1,5-a]quinoline and pyrazolo[1,5-a]indole intermediates were synthesized. Two target products were obtained by pyrazolo[1,5-a]indole intermediates reacting with methyl trifluoromethanesulfonate and 4-dimethylaminobenzaldehyde. Two derivatives were obtained by 4,5-dihydropyrazolo[1,5-a]quinoline intermediates reacting with methyl trifluoromethanesulfonate. Two derivatives were obtained by dehydrogenation of 4,5-dihydropyrazolo[1,5-a]quinoline intermediates. Some of the derivatives and three of the 4,5-dihydropyrazolo[1,5-a]quinolines were screened for pharmacological activity and some compounds showed potent anticancer activity.