Aryl Halides and Alcohols

Palladium-catalyzed carbonylation of aryl halides with nucleophiles such as alcohols, amines, and water can be performed in ionic liquid media. Several systems have been designed so that the ionic phase can be isolated and recycled. Once carbonylation substrates/products form homogeneous mixtures with ionic liquids, the experimental protocols for catalyst/ionic liquid mixture recycling involve separation of the product by either distillation or extraction procedures using organic solvents or supercritical CO2. 

The methoxycarbonylation of bromobenzene yielding methyl benzoate promoted by Pd(OAc)2 can be performed in ionic liquid media (BMI BF4 and BMI-PF, entry 1, Table 6.3) with better yields when compared with the classical homogeneous system using methanol as a solvent. A 20-fold excess PPha relative to palladium was found to be necessary to prevent catalyst decomposition to metaDic palladium the ionic 

The beneficial effect of the addition oftetraalkylammonium salts was observed in the methoxycarbonylation of iodobenzene with PdCl2(COD) and PdCl2(P(OPh)3)2 [54]. In a reaction catalyzed by PdCl2(COD) at 40 °C and 1 atm of CO in methanol, the ester yield increased from 14 to 5 2% when BU4N Cl was added, with no formation of palladium black. Almost quantitative yield of ester was obtained in molten BU4N Cl at 80 °C and 5 atm of CO (entry 3, Table 6.3). 

A systematic study of the influence of different ionic liquids on the activity of the methoxycarbonylation of iodobenzene promoted by Pd colloids reveals the structure dependence on the catalytic activity tetraalkyl ammonium and pyridinium salts are much more effective additives than imidazolium-based ILs to stabilize palladium colloids. The yield of methoxycarbonylation reaction catalyzed by Pd colloid decreases in the following order NBu4-Br NBu4-I NBu4-Cl BMpy-PFe  

Carbonylation of 17-iodo-5a-androst-16-ene in the presence of methyl glycinate or morpholine using Pd(OAc)2/phosphine can be performed in BMI BF4 and BMI PF media (entries 8-9, Table 6.3), and the IL-catalyst mixture can be reused up to five times before losses in catalytic activities were observed [58,59]. The methodology could be extended for the aminocarbonylation of other steroids with 17-iodo-5a-androst-16-ene functionality. Other interesting examples of carbonylation reactions 

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