Convergent Synthesis of Triindanone-Fused Spiro[bicyclo[2.2.2]octane-2,3'-indolines] via Domino Reaction of 1,3-Indanedione and 3-Methyleneoxindoles.

A triethylamine-promoted domino reaction of three molecular 1,3-indanediones with various 3-methyleneoxindoles in refluxing ethanol has been developed. Series of novel polycyclic triindanone-fused spiro[bicyclo[2.2.2]octane-2,3'-indoline] derivatives were successfully synthesized in satisfactory yields with high diastereoselectivity. This domino reaction was accomplished with in situ generation of active cyclic dienes by base-promoted cyclotrimerization or cyclotetramerization of 1,3-indanediones and sequential Diels-Alder reaction of active cyclic dienes with dienophilic 3-methyleneoxindoles.