Diversity-Oriented Synthesis of Spirocyclohexene Indane-1,3-diones and Coumarin-Fused Cyclopentanes via an Organobase-Controlled Cascade Reaction

An organobase-controlled, divergent cascade reaction to construct spirocyclohexene indane-1,3-diones and coumarin-fused cyclopentanes is reported. The cascade reaction is triggered by the 1,6-addition of 3-homoacylcoumarins to the indanedione-derived acceptors and further regio/chemoselective reaction that preferentially resulted in spiro systems and fused cyclopentanes in a diversity-oriented manner. The 1,6-addition/aldol and 1,6-addition/vinylogous Michael addition cascade processes were controlled by different base/solvent systems to the predominant formation of one of the two carbocyclic compounds.