“Diels-Alder reactions of arylethenes. Synthesis of some [5]phenacenes and fluorenoanthracenes”

A one-pot high yielding route to 3,4-dihydro-1-(2H)-anthracenone (9) based on high pressure Diels-Alder reaction is described. The synthesis of 3,4-dihydro-1-vinylphenanthrene (1) and 3,4-dihydro-1-vinylanthracene (2) is reported. A new synthetic two-step approach to [5]phenacenes and fluorenoanthracenes has been developed. It is based on the Diels-Alder reaction of arylethenes 1 and 2 with benzyne (13), 1,4-benzoquinone (14), 1,4-naphthoquinone (15) and inden-1-one (17) and on the aromatization of the cycloadducts. Structure analysis of the reaction products by 1H and 13C- NMR spectroscopy is presented.