Inner–outer ring 1,3-bis(trimethylsilyloxy)-1,3-dienes as useful intermediates in the synthesis of helicenes

Functionalized benzo[c]phenanthrenes ([4]helicenes) and [5]helicenes were synthesised in five steps from tetrahydronaphthalenone and tetrahydrophenanthrenone compounds using a novel synthetic approach based on a Diels–Alder reaction between inner–outer ring 1,3-bis(trimethylsilyloxy)-1,3-dienes and benzyne or quinones.