title: A convenient approach to heterocyclic building blocks: synthesis of novel ring systems containing a [5,6]Pyrano[2,3-c]pyrazol-4(1H)-one moiety.
abstract: Starting from commercially available educts, a straightforward synthetic route to new heterocyclic building blocks is exemplified with the one- or two-step synthesis of tri-, tetra-, or pentacyclic ring systems. Representatives of the following novel ring systems are prepared from 3-methyl-1-phenyl-2-pyrazolin-5-one and the corresponding o-halo-arenecarbonyl chloride using calcium hydroxide in refluxing 1,4-dioxane: pyrimidino[4',5':5,6]pyrano[2,3-c]pyrazol-4(1H)-one, thieno[3',2':5,6]pyrano[2,3c]pyrazol- 4-(1H)-one, thieno[3',4':5,6]pyrano[2,3-c]pyrazol-4(1H)-one, thieno[3'',2'':4',5']thieno[2',3':5,6]-pyrano[2,3-c]pyrazol-4(1H)-one, [1,3]dioxolo[5',6'][1]benzothieno[2',3':5,6]pyrano-[2,3-c]- pyrazol-4(1H)-one, pyridazino[4',3':5,6]pyrano[2,3-c]pyrazol-4(1H)-one and pyrazolo-[4'',3'':5',6']pyrido[3',4':5,6]pyrano[2,3-c]pyrazol-4(1H)-one. While the latter two ring systems are directly obtained due to a spontaneous intramolecular substitution reaction, in the other reactions uncyclised 4-aroylpyrazol-5-ols are produced, which are cyclised into the target heterocycles in a subsequent synthetic step (i.e. treatment with NaH in DMF). Detailed NMR spectroscopic investigations ((1)H-, (13)C-, (15)N-) with the obtained compounds were undertaken to unambiguously prove the new structures.
authors: Department of Drug and Natural Product Synthesis, Faculty of Life Sciences, University of Vienna, Vienna, Austria. gernot.eller@univie.ac.at
authors: Gernot
authors: G
authors: Eller
authors: Wolfgang
authors: W
authors: Holzer
mesh_terms: D002247:Carbon Isotopes; D006571:Heterocyclic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D015394:Molecular Structure; D009587:Nitrogen Isotopes; D011714:Pyrans / Q000737:chemistry*; D011720:Pyrazoles / Q000737:chemistry*
chemical_list: D002247:Carbon Isotopes; D006571:Heterocyclic Compounds; D009587:Nitrogen Isotopes; D011714:Pyrans; D011720:Pyrazoles
references: Org Biomol Chem. 2006 Jun 21;4(12):2337-47
references: 16763676
references: Clin Drug Investig. 2005;25(9):555-66
references: 17532700
references: Molecules. 2006 Nov 29;11(11):915-28
references: 18007396
references: Curr Opin Drug Discov Devel. 2000 May;3(3):298-305
references: 19649862