Synthesis of Trifluoromethyl-Substituted Arenes, Cyclohexenones and Pyran-4-ones by Cyclocondensation of 1,3-Bis(silyloxy)-1,3-butadienes with 4,4-Dimethoxy-1,1,1-trifluorobut-3-en-2-one: Influence of the Lewis Acid on the Product Distribution
TiCl4-mediated formal [3 + 3] cyclocondensation of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with 4,4-dimethoxy-1,1,1-trifluorobut-3-en-2-one afforded a variety of functionalized 4-methoxy-6-(trifluoromethyl)salicylates and 3-methoxy-5-(trifluoromethyl)phenols with very good regioselectivity. The Me3SiOTf-mediated cyclization of 1,3-bis(trimethylsilyloxy)-1,3-butadienes, containing no substituent located