Photoreactions of Polyhalobenzenes in Benzene. Formation of Terphenyls

Abstract

Polychlorobenzenes, polybromobenzenes, and polychloropolybromobenzenes (C6H6−nXn) were photolyzed in benzene solutions; the products were analyzed by the GC/MS method. Both dehalogenation and phenylation were shown to take place competitively, producing (poly)halobenzenes bearing one less halogen atom (C6H7−nXn−1) and (poly)halobiphenyls (C6H6−nXn−1–C6H5) as the major products. Besides these products, terphenyl was produced by a consecutive phenylation of the halobiphenyl formed. Polychlorobenzenes were shown to form the corresponding terphenyls only when a pathway via 2-chlorobiphenyl is possible; however, polybromobenzenes can produce terphenyls through any of the isomeric bromobiphenyls intermediarily formed. Isomerization through m-migration of a chlorine atom was also shown to occur to a considerably lesser extent.

Fast Recombination of Charge-Transfer State in Organic Photovoltaic Composite of P3HT and Semiconducting Carbon Nanotubes Is the Reason for Its Poor Photovoltaic Performance

“…While the chemical structure of this precipitate is unclear at present, we suggest that it is the product of dechlorination of o-dichlorobenzene caused by ultrasonication followed by oligomerization or polymerization of phenyl rings. This is in line with the observed formation of terphenyls upon the photoreaction of o-dichlorobenzene solutions [ 53 ]. We suggest that the dechlorination of o-dichlorobenzene can be mechanically activated by ultrasound waves.…”

Studies on Pd/NiFe2O4 catalyzed ligand-free Suzuki reaction in aqueous phase: synthesis of biaryls, terphenyls and polyaryls

“…Polyphenyls are also an important structural element in liquid crystals and fluorescent compounds [ 48 – 52 ]. Terphenyls have been previously synthesized by the reaction of aryl- or benzylzinc reagents with functionalized biphenyl nonaflates [ 53 ], Grignard reagents with dihalobenzenes [ 54 – 56 ]: Other methods give poor yields. The Suzuki cross coupling protocol has been used for the synthesis of terphenyls and polyaryls using Pd(OAc) 2 or Pd(PPh 3 ) 4 with or without ligands in homogeneous medium [ 57 – 60 ].…”

A highly active and reusable heterogeneous catalyst for the Suzuki reaction: synthesis of biaryls and polyaryls

“…9 For example, terphenyls (o, m, p-isomers) are used industrially as heat storage and transfer agents and as textile dye carriers whilst the pisomer has found application as a laser dye. The transition metal catalysed cross-coupling of Grignard reagents with dihalobenzenes 10,11 and other methods 12 produce the desired terphenyls in poor yields. Recently, the synthesis of polyaryls has been reported 13 using palladium acetate in a domestic microwave oven.…”