Abstract. Starting from 2, 6-di (hydroxymethyl)-4-methylphen-dioxolan-4-ones (6a-h) as well as the corresponding ol-Na-salt-l-hydrate (1) a synthesis of 2-alkoxy-5-methyliso- bisdioxolanones (6i-I). Dehydrobromination of 2-aryl-5-phthaldialdehydes (3a, b) is described via alkylation and oxi- bromomethyl-l, 3-dioxolan-4-ones (6a-d, i) with DBU leads dation. Condensation of aromatic aldehydes with 3-bromo- to 2-aryl-5-methylene-l, 3- ...