Treatment of α-alkylcinnamaldehydes with orthoesters, alcohols, or thiols in the presence of BF3·OEt2 induces an intramolecularelectrophilicaromaticsubstitution reaction to afford 1-alkoxy-2-alkylindenes. The reaction mechanisms of the indene formation have been elucidated on the basis of the reaction behaviors of β-deuterated α-methylcinnamaldehyde and the NMR studies of the reaction mixture. The
Conversion of 2-Alkylcinnamaldehydes to 2-Alkylindanones via a Catalytic Intramolecular Friedel−Crafts Reaction
作者:Gary B. Womack、John G. Angeles、Vincent E. Fanelli、Christie A. Heyer
DOI:10.1021/jo070952o
日期:2007.8.31
3-arylpropanoic acids or halides requires the use of noncatalytic acid promoters. In the presence of 5−10 mol % 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 by treatment with triethylamine, to effect isomerization to the isomeric enol ethers
The present invention relates to a process for making indenol esters or ether from an α-substituted cinnamic aldehyde derivative such as an acetal or an acylal. This reaction is promoted by the use of strong mineral acids, sulphonic acids, acidic zeolites or Lewis acids.