Cyclization of 1-hydroxy-2-(oxoalkynyl)anthraquinones

Abstract

Procedures were developed for the heterocyclization of 2 benzoylethynyl 1 hydroxy and 1 hydroxy 2 (1 oxo 3 phenylpropynyl)anthraquinone. The regioselective preparation of 2 substituted anthra[1,2 b]pyran 4,7,12 triones was demonstrated to be possible under mild conditions.

The synthesis and biological activity of novel anthracenone-pyranones and anthracenone-furans

“…This tactic has been pursued by several groups including that of Shvartsberg. 24,25 The anthraquinone-yne-one could be prepared either using a Castro-Stevens reaction or the related Sonogashira palladium catalysed process. Thus treatment of benzoyl protected phenol 5 with phenyl copper acetylene 6 provided the yne-one 7 in excellent yield (95%).…”

“…Thus treatment of benzoyl protected phenol 5 with phenyl copper acetylene 6 provided the yne-one 7 in excellent yield (95%). 24 Subjection of compound 7 to sulphuric acid provided the phenyl 4-pyranone 8 in 55% yield through hydration of the alkyne and cyclisation through a phenoxide. Alternatively, hydration using p-TsOH provided a crude mixture of the isopropyl-ether 4-pyranone and phenol-4-pyranone 8 (1:3.7 by NMR analysis of the crude product).…”

“…As this annulation process was low yielding we decided to pursue a more efficient synthetic route. Unfortunately, following the piperidine and aminovinyl ketone method devised by the Shvartsberg group, 24 only afforded a complex mixture of products.…”

“…[43][44][45][46] In several examples ortho-substituted halides had previously been used in heterocycle synthesis including both furans and isocoumarins, while in situ quenching of these reactions have been reported to produce pyrazoles. 24 poor solubility of cuprous acetylides these species were analysed by elemental analysis and used without further purification (ESI ). Following the original Castro-Stevens protocol we trailed reactions in pyridine at high temperatures in order to solubilise the copper acetylide.…”

Pd-catalyzed cross-coupling/heterocyclization domino reaction: facile access to anthra[2,3-b]furan-5,10-dione scaffold

“…12e18 A similar methodology has been previously adapted for the synthesis of anthra [2,3-b]furan-5,10-diones. 19,20 For instance, 2-phenylanthra [2,3-b]furan-5,10-dione was readily prepared by cross-coupling of 2-hydroxy-3-iodoanthraquinone with phenylacetylene using Pd(PPh 3 ) 2 Cl 2 /CuI as the catalyst. However, the heterocyclization described above to anthra[2,3-b]furan-5,10-diones is poorly suitable for the synthesis of biologically active compounds in this series.…”