Aryl chlorides tricyclohexylphosphine

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]. 

Recently, the groups of Fu and Buchwald have coupled aryl chlorides with arylboronic acids [34, 35]. The methodology may be amenable to large-scale synthesis because organic chlorides are less expensive and more readily available than other organic halides. Under conventional Suzuki conditions, chlorobenzene is virtually inert because of its reluctance to oxidatively add to Pd(0). However, in the presence of sterically hindered, electron-rich phosphine ligands [e.g., P(f-Bu)3 or tricyclohexylphosphine], enhanced reactivity is acquired presumably because the oxidative addition of an aryl chloride is more facile with a more electron-rich palladium complex. For... 

Bedford and co-workers have demonstrated that palladium complexes of the simple, inexpensive tricyclohexylphosphine display very high activity in the Stille coupling of non-activated and deactivated aryl chlorides [Equation (5.3.6)]The use of K3PO4 is necessary to promote the coupling. 

Subsequently, Ackermann reported that 1,2,3-triazoles can be arylated by aryl chlorides even if conventional heating to 105-120°C is employed [41], Tricyclohexylphosphine ligand combination with palladium acetate was shown to be the... 

Among the nickel-based catalysts, beside the nickel on charcoal [43], mainly the various nickel(0)-phosphine complexes were employed [12,13,44,45]. Several common bidentate phosphine ligands such as dppf, dppe, dppp, dppb and tricyclohexylphosphine (PCys) are the most popular in the nickel-based SM crosscoupling reactions of less reactive aryl chlorides with arylboronic acids [44], While the nickel complexes of electron-rich trialkylphosphines react readily with aryl chlorides. 

An important observation regarding Suzuki couplings of aryl chlorides was reported in 1997 by Shen, who established that palladium complexes that include a bulky, electron-rich trialkylphosphine, such as tricyclohexylphosphine (PCys), catalyze Suzuki couphngs of activated aryl chlorides at 100°C (Equation 2.14) [25]. 

Nickel(O) complexes tend to undergo oxidative addition of aryl halides faster than palladium(O) complexes. There are some drawbacks to the use of the nickel complexes, described above, that can outweigh the lower cost of nickel. Nevertheless, the ruckel complexes containing triarylphosphines do undergo oxidative addition of aryl chlorides (Equation 19.39) and tosylates (Equation 19.40), and some mild conditions have been developed for nickel-catalyzed cross couplings of aryl chlorides and aryl tosylates with ligands such as triphenylphosphine or tricyclohexylphosphine. ... 

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