Benzylidene tetralone

Reaction of the 2-ethoaynaphthopyran (70) derived from the cycloaddition of vinyl ether to the benzylidene tetralone (69) with hydroxylamine affords 5,6-dihydrobenzo[h]quinolines (M. C. Bellassoued-Fargeau and P. Maitte, J. heterocyclic Chem., 1984, 21, 1549). 

A carboxyl functionality can be introduced at C-2 by this method an a-keto acid or ester reacts with a chalcone under the usual conditions (68CB2215, 82JOC492), whilst benzylidene-l-tetralone affords the naphthopyrylium salt (669) (82JOC498). 

The reagent is prepared by reaction of 2-benzylidene-a-tetralone with a-tetralone in the presence of BF3 etherate (42% yield).1... 

There are also a few examples of poly-amino add catalyzed epoxidation of non-linear enones. These indude tetralone derivatives 47, which can be epoxidized with good yields and enantiomeric excesses the best results were achieved for R = p-02N-QH4 and n = 1 (85% 96% ee) [84]. Other examples are the epoxidation of "iso-chalcone 48 (78% 59% ee) [69] or of bis-benzylidene cyclohexanone 49, which affords the corresponding bis-epoxide of good optical purity [69]. 

The synthesis [25, 26] began with 7-bromo-l-tetralone (7), available in multigram quantity in three steps from succinic anhydride and bromobenzene [27, 28] (Scheme 1). Treatment of 7 with an aromatic aldehyde and base produces the corresponding benzylidene (e.g., 8) which couples with 7 in boron trifluoride etherate to form a pyrylium salt. This pyrylium salt is not isolated but treated with ammonia to afford functionalized spacer 9. As seen in Scheme 1, the attachment of anthracene [29] or acridine chromophores occurs in a single step. Alternatively, stepwise attachment of the aromatic chromophores allows construction of molecular tweezers 12 and 13 carrying different chromophores. With respect to efficiency, tweezers 10 and 11 are synthesized in six steps from inexpensive starting materials with overall yields of 11% and 14%, respectively. 

Aboraia AS, Makowski B, Bahja A, Prosser D, Braneale A, Jones G, Simons C (2010) Synthesis and CYP24A1 inhibitory activity of (E)-2-(2-substituted benzylidene)- and 2-(2-substituted benzyl)-6-methoxy-tetralones. Eur J Med Chem 45 4427 434... 

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