The present invention relates to compounds of the formula I where one or more of the radicals A1-5 denote a 1,4-naphthylene or 1,4- or 9,10-anthracenylene radical, and the other parameters are as defined in Claim 1. The invention additionally includes liquid-crystalline media which comprise the title compounds, and components for high-frequency technology which comprise these media, in particular phase shifters and microwave array antennae.