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(1
H)-one, thieno[3',2':5,6]pyrano[2,3
c]pyrazol- 4-(1
H)-one, thieno[3',4':5,6]pyrano[2,3-
c]pyrazol-4(1
H)-one, thieno[3'',2'':4',5']thieno[2',3':5,6]-pyrano[2,3-
c]pyrazol-4(1
H)-one, [1,3]dioxolo[5',6'][1]benzothieno[2',3':5,6]pyrano-[2,3-
c]- pyrazol-4(1
H)-one, pyridazino[4',3':5,6]pyrano[2,3-
c]pyrazol-4(1
H)-one and pyrazolo-[4'',3'':5',6']pyrido[3',4':5,6]pyrano[2,3-
c]pyrazol-4(1
H)-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 (
1H-,
13C-,
15N-) with the obtained compounds were undertaken to unambiguously prove the new structures.
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