Domino reaction of bindone and 1,3-dipolarophiles for the synthesis of diverse spiro and fused indeno[1,2-a]fluorene-7,12-diones†
The base promoted domino reaction of bindone ([1,2′-biindenylidene]-1′,3,3′-trione) with common 1,3-dipolarophiles showed interesting molecular diversities, from which the unique spiro and fused indeno[1,2-a]fluorine derivatives were conveniently synthesized in satisfactory yields. In the presence of a base, bindone underwent formal [3 + 3] cycloaddition with satylidene malononitriles to give dispiro[indene-2,4′-fluorene-1′,3′′-indoline]. It also underwent formal [4 + 2] cycloaddition with 4-arylidene-pyrazol-3-ones to give diastereoisomeric spiro[indeno[1,2-a]fluorene-5,4′-pyrazole]. On the other hand, a triethylamine promoted reaction of three molecules of 1,3-indanediones and isatins in toluene afforded spiro[diindeno[2,1-b:2′,1′-d]anthracene-11,3′-indoline] derivatives through the domino [4 + 2] cycloaddition and ring-expansion process.