Synthesis and study of 10-(4-methoxybenzylidene)-9(10H)-phenanthrone, a stable ortho-quinone methanide

Abstract

The reaction of phenanthrene-9,10-quinone 1 with 1 or 2 equiv. of the ylide 2f under phase transfer catalysis conditions afforded either solely the stable o-quinone methanide 3f or mainly compound 3f along with compound 4c respectively. The reactions of compound 3f gave: (a) with ylides 2f, 2h the dihydrofurans 4c and 4d; (b) with ylide 2c the pyranones 13 and 16; (c) with ylides 2d and 2g the cyclobutenes 6c and 6d; (d) with vinyl ethers the pyrans 11d and 11e; and (e) with alcohols 25a,b the ethers 26a,b. By prolonged heating in refluxing toluene compound 3f dimerizes to the spiro compound 22. The reactions of compounds 16 and 6d with N-bromosuccinimide (NBS) were also studied.