Aryl bromides tricyclohexylphosphine

A similar general method for the rhodium-catalyzed direct coupling of benzimidazoles with aryl bromides or iodides has also been developed under microwave-assisted conditions, and it has shown to provide rapid access to medicinally relevant compounds. Both electron-rich and electron-poor aryl iodides were observed to couple with tricyclohexylphosphine. The desired... 

Triphenylphosphine afforded mixtures of mono- and diarylated products, whereas tricyclohexylphosphine produced exclusively the C3-arylated product. Aryl bromides bearing electron-donating and electron-withdrawing substituents were well tolerated. Heteroaryl bromides, such as 3-bromothiophene and 3-bromofurane, were low yielding (24 and 18%) extended reaction times and the addition of pivalic acid failed to improve conversions. 

C5-arylation of iV-protected L-histidine could be achieved using microwave irradiation via a Pd-catalyzed process employing pivalic acid and tricyclohexylphosphine (eq 2 ) Other phosphines, such as PPhs and P(2-furyl)3, produced diminished conversions. Moderate yields could be obtained without a ligand (54%), albeit tricyclohexylphosphine was required to maximize product formation. Good functional group tolerance was observed for aryl iodide coupling partners orf/zo-substitution and sensitive groups, such as cyano, nitro, ester, and chloro substrates, were compatible. Aryl bromides could also be employed, albeit with diminished yields (10-18%). 

Cyclopropane C( p )-H bond functionalization has been reported in the reaction of aryl bromide and tricyclohexylphosphine as an achiral ligand on palladium to give tetrahydroquinoline (Scheme 138). ... 

Usually, iodides and bromides are used for the carbonylation, and chlorides are inert. I lowever, oxidative addition of aryl chlorides can be facilitated by use of bidcntatc phosphine, which forms a six-membered chelate structure and increa.scs (he electron density of Pd. For example, benzoate is prepared by the carbonylation of chlorobenzene using bis(diisopropylphosphino)propane (dippp) (456) as a ligand at 150 [308]. The use of tricyclohexylphosphine for the carbonylation of neat aryl chlorides in aqueous KOH under biphasic conditions is also recommended[309,310]. 

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