tert-Butyl methyl ether → 3-Fluoro-4'-pentyl-4-(trifluoromethoxy)biphenyl-2-carbaldehyde

Participants

Reaction Steps

A mixture of 98 mmol of 2-bromo-6-fluoro-5-trifluoromethoxybenzaldehyde (Example 1), 112 mmol of 4-pentylphenylboric acid, 225 mmol of cesium fluoride (anhydrous) and 3.4 mmol of tetrakis(triphenylphosphine)palladium(0) in 480 ml of dimethoxyethane is heated to boiling until the reaction is complete. After cooling, the reaction mixture is admixed with tert-butyl methyl ether and water. The organic phase is washed with water and saturated NaCl solution and dried over sodium sulfate, and the solvents are removed under reduced pressure. After chromatographic purification of the crude product (silica gel, heptane/ethyl acetate 9:1), followed by recrystallization from heptane, 3-fluoro-4′-pentyl-4-(trifluoromethoxy)biphenyl-2-carbaldehyde is obtained in the form of colorless crystals. From this, the reaction sequence described in DE-A-101 01 020 (oxidation to the carboxylic acid, conversion to the acid chloride, intramolecular Friedel-Crafts reaction, reduction with triethylsilane) provides 1-fluoro-7-pentyl-2-(trifluoromethoxy)fluorene which, according to DE-A-101 01 020, finds use as a component of nematic or smectic liquid crystal mixtures.

Provenance & Evidence