Meldrum intramolecular Friedel-Crafts

Intramolecular Friedel-Crafts reaction Worthy of mention is the case of intramolecular Friedel-Crafts-type reaction affording 4(lH)-quinolone derivatives [443]. Thus, after extensive investigations, the authors prepared a solid-supported Meldrum s acid derivative by alkylation of a Merrifield resin with ethyl acetoacetate, decarboxylation, and subsequent ketalization of the resulting supported ketone with malonic acid (638). Treatment with triethyl orthoformate and various arylamines (639) afforded immobilized arylamino-methylene derivatives of Meldrum s acid (640). Upon thermal cyclization, these intermediates afforded 4(lH)-quinolone derivatives with simultaneous release from the resin (641). Highly pure final compounds were obtained in moderate to good yields. The resin was recovered in the form of the precursor of (638), i.e., the ketone (642), and thus could be potentially reused (Scheme 133). 

Pillion, E. and Fishlock, D. 2003. Convenient access to polysubstituted 1-indanones by Sc(OXf)3-catalyzed intramolecular Friedel-Crafts acylation of benzyl Meldrum s acid derivatives. Org. Lett. 5 4653 656. 

Intramolecular Friedel-Crafts acylation of enolizable benzyl Meldrum acids 22 wifh scandium triflate (7%-12% mol) in refluxing nitromethane or acetonitrile is a powerful tool for the preparation of a variety of indan-l-ones 23 (Table Meldrum acid derivatives, mono- and dis-... 

Fillion, E., Fishlock, D., Wilsily, A., and Goll, J. M. 2005. Meldrum s Acids as acylating agents in the catalytic intramolecular Friedel-Crafts reaction. /. Org. Chem. 70 1316-1327. 

The intramolecular Friedel-Crafts acylation of benzyl Meldrum s acids was catalyzed by Sc(OTf)3 under mild conditions (Scheme 12.25) [54]. Depending on the substituents of the benzyl Meldrum s acids, yields of 1-indanones ranged from 13 to 83%. 

Friedel-Crafts Reactions. Aluminum trifluoromethanesulfonate has been used for the Friedel-Crafts alkylation reaction of toluene with isopropyl and tert-butyl chlorides (eq 1), and for the acylation of benzene and toluene with acetyl and benzoyl chlorides in low to moderate yields. Intramolecular Friedel-Crafts acylation of an aromatic compound with Meldrum s acid has also been reported using catalytic amounts of Al(OTf)3. Acylation of 2-methoxynaphthalene with acetic anhydride has been reported using Al(OTf)3 and lithium perchlorate as an additive to afford the corresponding 6-acetylated adduct in 83% yield. Effective acylation of arenes with carboxylic acids has also been disclosed using polystyrene-supported Al(OTf)3. ... 

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