when necessary. The systems dealing with the C(vinyl)–N bond formation
catalyzed by copper constitute a part of the chapter presented by C. Bolm, as a
chapter written by M. L. Kantam is dealing with the related heterogeneous systems.
2 C–N Bond Formation from Aryl Halides
By far the greatest number of reports on the modern catalytic Ullmann-type
reactions has dealt with the creation of C–N bonds. Amongst the numerous
publications which appeared during the last decade, those that give real improvement in terms of overall efficiency have been selected. Many other systems, though
they are very interesting contributions, cannot be included within the scope of this
book chapter.
2.1 Coupling Reactions of Aryl Halides with N-Heterocycles
and Cyclic Amides
Some years ago we developed novel families of polydentate ligands of Schiff base
and oxime type (L1–L4). Combining at least one imine with oxygen or nitrogen
coordination sites (Scheme 1), they facilitate coupling of numerous azole and cyclic
amide derivatives (Table 1, entry 1) with aryl bromides under mild temperature
conditions
, [36–39], [41–43]. With aryl iodides, some reactions were even performed
at 25
C and a turnover of about 1,500 was achieved with pyrazole at higher
temperature (80
C). This catalytic system is one of the rare examples amongst
modern copper chemistry that has already been industrially applied.
Another catalytic system was developed by Bao using the β-ketoester ligand L5
(Table 1, entry 2) [44]. Coupling of different N-nucleophiles at mild temperatures
with aryliodides or bromides mainly substituted by electron-donating groups was
reported. Note that reactions could be conducted at room temperature from phenyl
iodide or bromoiodobenzene and pyrrolidinone.
Amino acids, especially L-proline L6 and N,N-dimethylglycine L7, were shown
by Ma and co-workers to be excellent bidentate ligands for copper-catalyzed
Ullmann-type reactions [45–48]. They successfully enabled coupling of numerous
aryl bromides with various azoles, often in mild temperature conditions (Table 1,
entry 3). The low cost of naturally occurring amino acids and their availability
provide a real interest to Ma’s system.
The butadienylphosphine L8 and related molecules, obtained from a synthetic
method based on the phosphorus ylides, are efficient ligands in Ullmann-type
copper-catalyzed arylation reactions, particularly for nitrogen heterocycles
(Table 1, entry 4). The reactions often proceed to completion in a very short time.
Copper-Catalyzed C(aryl)–N Bond Formation
175
catalyzed by copper constitute a part of the chapter presented by C. Bolm, as a
chapter written by M. L. Kantam is dealing with the related heterogeneous systems.
2 C–N Bond Formation from Aryl Halides
By far the greatest number of reports on the modern catalytic Ullmann-type
reactions has dealt with the creation of C–N bonds. Amongst the numerous
publications which appeared during the last decade, those that give real improvement in terms of overall efficiency have been selected. Many other systems, though
they are very interesting contributions, cannot be included within the scope of this
book chapter.
2.1 Coupling Reactions of Aryl Halides with N-Heterocycles
and Cyclic Amides
Some years ago we developed novel families of polydentate ligands of Schiff base
and oxime type (L1–L4). Combining at least one imine with oxygen or nitrogen
coordination sites (Scheme 1), they facilitate coupling of numerous azole and cyclic
amide derivatives (Table 1, entry 1) with aryl bromides under mild temperature
conditions
, [36–39], [41–43]. With aryl iodides, some reactions were even performed
at 25
C and a turnover of about 1,500 was achieved with pyrazole at higher
temperature (80
C). This catalytic system is one of the rare examples amongst
modern copper chemistry that has already been industrially applied.
Another catalytic system was developed by Bao using the β-ketoester ligand L5
(Table 1, entry 2) [44]. Coupling of different N-nucleophiles at mild temperatures
with aryliodides or bromides mainly substituted by electron-donating groups was
reported. Note that reactions could be conducted at room temperature from phenyl
iodide or bromoiodobenzene and pyrrolidinone.
Amino acids, especially L-proline L6 and N,N-dimethylglycine L7, were shown
by Ma and co-workers to be excellent bidentate ligands for copper-catalyzed
Ullmann-type reactions [45–48]. They successfully enabled coupling of numerous
aryl bromides with various azoles, often in mild temperature conditions (Table 1,
entry 3). The low cost of naturally occurring amino acids and their availability
provide a real interest to Ma’s system.
The butadienylphosphine L8 and related molecules, obtained from a synthetic
method based on the phosphorus ylides, are efficient ligands in Ullmann-type
copper-catalyzed arylation reactions, particularly for nitrogen heterocycles
(Table 1, entry 4). The reactions often proceed to completion in a very short time.
Copper-Catalyzed C(aryl)–N Bond Formation
175