No abstract

An experimentally simple and inexpensive catalyst system was developed for the amidation of aryl halides by using 0.2-10 mol % of CuI, 5-20 mol % of a 1,2-diamine ligand, and K(3)PO(4), K(2)CO(3), or Cs(2)CO(3) as base. Catalyst systems based on N,N'-dimethylethylenediamine or trans-N,N'-dimethyl-1,2-cyclohexanediamine were found to be the most active even though several other 1,2-diamine ligands could be used in the easiest cases. Aryl iodides, bromides, and in some cases even aryl chlorides can be efficiently amidated. A variety of functional groups are tolerated in the reaction, including many that are not compatible with Pd-catalyzed amidation or amination methodology.

The first general method for the Pd-catalyzed amination of aryl tosylates and benzenesulfonates was developed utilizing ligand 1, which belongs to a new generation of biaryl monophosphine ligands. In addition, the new catalyst system for the first time enables amidation of aryl arenesulfonates and aqueous amination protocols that do not necessitate the use of cosolvents. The substrate scope has been significantly expanded to include aryl halides containing primary amides and free carboxylic acid groups. In the case of multifunctional substrates, the Pd-catalyzed amination can provide selectivity that is complementary to the Cu-catalyzed C-N bond-forming processes.

Bulky, electron-rich phosphine ligands with a biphenyl backbone, when combined with Pd(OAc)2, give highly active catalysts for the α-arylation of ketones. The ligand 2-methyl-2‘-dicyclohexylphosphinobiphenyl is particularly effective, and with 0.1−1.0 mol % Pd, a large variety of aryl halides and ketones react efficiently and with high selectivity. For two types of substrates, the ligands BINAP and Xantphos are more effective than the biphenyl-based ligands. It is also shown that K3PO4 can be used as the base in these reactions, and that base-sensitive functional groups are better tolerated if this is used instead of NaO t Bu or NaHMDS. In some cases, α-aryl ketones can be produced without adding a ligand to the reaction. Although the substrate scope of the ligandless conditions is limited, some combinations react in high yield, and in one case, 100 000 turnovers were obtained. The results of experiments on the Pd-catalyzed arylation of diethyl malonate, cyclic 1,3-diketones, and nitroalkanes are also reported.

A variety of diaryl ethers were synthesized by the Pd‐catalyzed reaction of (hetero)aryl halides and phenols. These reactions were achieved through the use of two new di‐tert‐butylphosphino biaryl ligands that overcome several limitations of previously described methods.