Synthesis of indenes via aluminum chloride-promoted tandem Friedel–Crafts alkylation of arenes and cinnamaldehydes

• Tandem Friedel–Crafts reaction of arenes and cinnamaldehydes was investigated.
• The cascade reaction affords indenes in good yields.
• The scope, limitation, and mechanism of the tandem reaction were explored.
• 1-Phenylindenes generated through a tandem reaction.
• 1,3-Diphenylindenes generated through a complex cascaded reaction.

A series of substituted indenes were synthesized from arenes and cinnamaldehydes via aluminum chloride-promoted tandem Friedel–Crafts alkylation. The scope and limitation of the tandem reaction were explored. A plausible reaction mechanism is also discussed. This approach provides a convenient method for the synthesis of indene derivatives using a readily available and low cost Lewis acid and starting materials.

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