Conversion of 2-Alkylcinnamaldehydes to 2-Alkylindanones via a Catalytic Intramolecular Friedel-Crafts Reaction

Gary B. Womack,* John G. Angeles, Vincent E. Fanelli and Christie A. Heyer

*Firmenich, Corporate R&D Division, P.O. Box 5880, Princeton, New Jersey 08543, Email: gary.womackfirmenich.com

G. B. Womack, J. G. Angeles, V. E. Fanelli, C. A. Heyer, J. Org. Chem., 2007, 72, 7046-7049.

DOI: 10.1021/jo070952o

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Abstract

The preparation of indanones by the intramolecular acylation of 3-arylpropanoic acids or halides requires the use of noncatalytic acid promoters. In the presence of a catalytic amount FeCl₃, in situ generated dimethyl acetals of (E)-2-alkylcinnamaldehydes cyclize to 1-methoxy-2-alkyl-1H-indenes in good-to-high yields. The 1-methoxyindenes were converted in high yield into 2-alkylindanones.

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Key Words

Friedel-Crafts Reaction, Indenes, Indanones

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ID: J42-Y2007-2880