1-Bromo-4-Decylbenzene for Liquid Crystal Material Synthesis
Jankowiak, Aleksandra, et al. Liquid Crystals, 2008, 35.1, 65-77.
Among new nematic and tilted smectic liquid crystal materials with negative dielectric anisotropy, fluorinated biphenyls and their derivatives are a particularly valuable class of materials. Among the fluorinated biphenyls are their 4-(2-cylcohexylethyl) derivatives of the general structure 1. Several of these compounds containing an alkoxy (R=OAlkyl), an alkyl (R=C5H11) or an ester group (R=COOCHMeC6H13) were investigated as smecto-genic materials. Decyl derivatives of fluorinated biphenyl can be prepared by the Suzuki coupling reaction of 1-Bromo-4-decylbenzene with boronic acid.
Synthesis of the fluorinated biphenyl decyl derivative
· The 19-Decyl-2,3-difluoro-4-(2-(E-4-pentylcyclohexyl)-ethyl)-biphenyl 1a was prepared in a Suzuki coupling reaction of boronic acid 5 and 1- bromo-4-decylbenzene (7) according to a general procedure.
· The crude product was passed through a silica gel plug, which was washed with hexanes. The eluent was evaporated leaving 22 mg (49% yield) of the crude product as a glassy solid. The analytical sample was obtained by recrystallization from EtOH/AcOEt followed by MeCN/toluene at -10°C.
Synthetic Pathway of 1-Bromo-4-Decylbenzene via Suzuki-Miyaura Cross-Coupling Reaction
Di Franco, et al. Synthesis, 2013, 45(21), 2949-2958.
Using nickel(II) pincer complex [(MeN2N)Ni-Cl] as the catalyst, alkyl-alkyl Suzuki -Miyaura coupling reaction by catalyzing 9-borabicyclo[3.3.1]nonane (9-BBN) and unactivated alkyl halide can successfully prepare 1-bromo-4-decylbenzene with a yield of 65%.
Alkyl-Alkyl Coupling Reactions
· To a solution of NaOH (32 mg, 0.8 mmol, 1.6 equiv), catalyst 1 (8.4 mg, 0.025 mmol, 5 mol%), NaI (37 mg, 0.25 mmol, 0.5 equiv), and i-PrOH (76 μL, 1 mmol, 2 equiv) in dry 1,4-dioxane (2.4 mL), were added 1-bromo-4-(2-bromoethyl)benzene (2j, 0.5 mmol) and the alkyl-(9-BBN) (1.6 mL, 0.8 mmol, 1.6 equiv) under a N2 atmosphere.
· The mixture was stirred at 80 °C for 24 h. The solution was diluted in Et2O (10 mL), filtered on a short pad of silica, washed with Et2O (3 × 10 mL), and concentrated to dryness under reduced pressure. The residue was purified with a flash purification system to give the coupling product 1-bromo-4-decylbenzene (3j).
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