Bromovinyl benzene

Metallation of the bis(bromovinyl)benzene 7 with t-butyllithium, followed by treatment with phenyldichlorophosphine, provides a route to the benzo-... 

Suzuki-Miyaura cross-coupling polymerization of 1,4-bis((Z)-2-bromovinyl)benzenes with aryl-bis-boronic acids. The interest has been in an alternative approach, where rather than building a PPV with a pre-ordained stereochemistry, a postpolymerization yyn-selective reduction on a poly(phenylene ethynylene) (PPE) is used [125]. This scheme has the advantage that high molecular weight PPEs can be synthesized using either Pd-catalysis or alkyne metathesis. This route could also potentially allow for the access to an additional array of PPVs that are uniquely accessible from PPEs. The transformation of the triple bonds in PPEs and other acetylene building blocks to alkenes has considerable potential. 

CAS 103-64-0 EINECS/ELINCS 203-131-3 Synonyms 1-Bromo-2-p-phenylethylene a-Bromo-p-phenylethylene u-Bromostyrene Bromostyrol Bromostyrolene (2-Bromovinyl) benzene Bromstyrol p-Bromstyrol Bromstyrole Hyacinth base Styrene, p-bromo-... 

Along with these E-alkenyl examples, (Z)-(2-bromovinyl)benzene (157) also underwent cyanation under the reaction conditions, albeit more slowly than its E counterpart 148, with a substantial proportion of the substrate unreacted after the 6 h reaction time (Table 7.7, Entry 6). A small amount of isomerisation was also observed in this case, with a Z E ratio of 12 1 in the crude mixture, as judged by integration of the NMR spectrum, although the two isomers proved chromato-graphically separable, allowing 158 to be isolated as a single isomer in 55 % yield. 

Pd(PPh3)4 (173 mg, 0.150 mmol) and tributyltin hydride (1.00 mL, 3.82 mmol) were added sequentially to a solntion of (2,2-dibromovinyl)benzene (1.00 g, 3.82 mmol) in CH2CI2 (15.0 mL), and the resultant mixture stirred at rt., in the dark, for 1.5 h. A solntion of potassinm fluoride (900 mg) in water (70 mL) was then added, and the mixtnre stirred for 18 h. The precipitate was removed by hltra-tion through a pad of silica, and the layers of the hltrate separated. The aqneons layer was extracted with CH2CI2 (2 x 100 mL), and the combined organics dried over MgS04 and concentrated nnder reduced pressure. The residue was purified by column chromatography (petrol) to afford (Z)-(2-bromovinyl)benzene (157) as a colourless oil. 

A mixture of 4-bromo-trani-cinnamic acid (1.59 g, 7.00 mmol), MBS (1.31 g, 7.35 mmol) and Mn(OAc)2 4H2O (343 mg, 1.40 mmol) in H2O (12.0 mL) and MeCN (12.0 mL) were stirred at rt. for 72 h. The mixture was then diluted with H2O (20 mL) and extracted with EtOAc (3 x 70 mL). The combined organics were dried over MgS04 and concentrated under reduced pressure. The residue was purified by column chromatography (petrol) to afford ( )-l-bromo -(2-bromovinyl)benzene (167) (561 mg, 31 %) as a white solid. 

Competition experiments indicated that aryl halides bearing electron-withdrawing groups were more reactive, producing accelerated rates of reaction compared with electron-donating groups. Both phenylboronic acid and ( )-(2-bromovinyl)benzene were also viable coupling partners (68 and 63% yield, respectively) (eq 37). 

---