Spiro heterocyclization of pyrrolo[2,1-c][1,4]benzoxazine-1,2,4-trione with dimedone

Reactions of substituted 2,3,-dihydro-1H-pyrrole2,3-diones, including those fused at the a bond to nitrogen-containing heterocycles, with enols were not reported previously. By reacting 3-p-bromobenzoyl2,4-dihydro-1H-pyrrolo[2,1-c][1,4]benzoxazine-1,2,4trione (I) with an equimolar amount of 5,5-dimethylcyclohexane-1,3-dione (II, dimedone) in boiling anhydrous benzene (reaction time 1.5 h), we obtained 3'-(4-bromobenzoyl)-4'-hydroxy-1'-(2-hydroxyphenyl)-6,6-dimethyl-2,2',3,4,5,5',6,7-octahydro-1'Hspiro[1-benzofuran-3,2'-pyrrole]-2,4,5'-trione (III) in almost quantitative yield. The spectral parameters of spiro compound III were very similar to those found for model octahydrospiro[indole-3,2'-pyrroles] whose structure was proved by X-ray analysis [1].