Xanthone undergoes regioselective substitution and nucleophically triggered ring opening to the corresponding ketone. Hydrazone of the latter oxidatively rearranges to ortho-diacylarenes, which, then, with hydrazine gives regioselectively substituted phthalazines. Molecular modeling analysis and H-1 NMR spectra indicate an intramolecular H-bonding engaging phenol OH and phthalazine N-3 atom.
Xanthone in synthesis: a reactivity profile via directed lithiation of its dimethyl ketal
作者:Michal R. Odrowaz-Sypniewski、Petros G. Tsoungas、George Varvounis、Paul Cordopatis
DOI:10.1016/j.tetlet.2009.08.050
日期:2009.11
Xanthone, as itsdimethylketal, undergoes functionalization with a synthetically useful degree of regioselectivity using a lithiation protocol. The core structure is regenerated during the work-up. Monosubstitution at C-4 or C-1 and disubstitution at C-4 and C-5 or C-1 and C-5 are observed. The substitution pattern appears to be dependent upon the experimental conditions.