Ullman coupling reactions

In a synthesis of decinine a phenol was protected as a methanesulfonate that was stable during an Ullman coupling reaction and during condensation, catalyzed by calcium hydroxide, of an amine with an aldehyde. Aryl methanesulfonates are cleaved by warm sodium hydroxide solution. " ... 

In general, imines are too reactive to be used to protect carbonyl groups. In a synthesis of juncusol, however, a bromo- and an iodocyclohexylimine of two identical aromatic aldehydes were coupled by an Ullman coupling reaction modi-fied by Ziegler. The imines were cleaved by acidic hydrolysis (aq. oxalic acid, THF, 20°, 1 h, 95% yield). Imines of aromatic aldehydes have also been prepared... 

The polymerization of a protected pyrrole has been reported based upon the Ullman coupling reaction [215,216,289]. As illustrated in Scheme 61, the 2,5-di-bromo-N-BOC-protected monomer was treated with CuCl followed by subsequent thermolysis to yield materials similar to those prepared in Scheme 60. Fractionation via HPLC made it possible to separate and characterize pyrrole oligomers up to n-20. 

This is an example of the Ullman coupling reaction. Other polyaromatic coupling reactions are provided (1). 

This instant invention represents an improvement in the Ullman coupling reaction. This investigation represents the first general method for coupling electron deficient phenols and unactivated aryl halides (1,2,3,4). The basis of the improvement lay in the high solubility of (CuOTf)2 benzene and cesium phenolate or copper phenolate in the reaction solvent, toluene. 

The mechanism of alkylation of AT-unsubstituted imidazoles and benzimidazole was discussed in CHEC(1984). Both CHEC(1984) and CHEC-II(1996) had extensive reviews on the topic, which are still relevant. A summary of improved Ullman coupling reactions is given in Table 9. 

Like the direct chemical change, the radical coupling mainly concerns fluorinated monomers. Ameduri and Boutevin [238] summarized the different studies concerning the modification of o ,rw-fluoropolymers in a recently published book. They showed, for instance, that extensive research [240] was carried out on the synthesis of diaromatic difunctional compounds linked to fluorinated chains according to the following Ullman coupling reaction ... 

Poly(phenylene ether) s with pendant perfluoroalkyl sulfonic acids with an ion exchange capacity of 1.17-1.83 equivalents/g have been synthesized by an aromatic nucleophilic substitution reaction of a perfluo-romonomer, such as decafluorobiphenyl or hexafluo-robenzene with 2,5-bis(4 -iodophenyl)hydroquinone, followed by a Ullman coupling reaction with potassium 1,1,2,2-tetrafluoro-2-(l, 1,2,2-tetrafluoro-2-iodoethoxy)ethanesulfonate [100]. 

The Ullman coupling reaction is known to proceed via arylcopper intermediates. Pertinent reviews have appeared on this subject (Bacon and Hill, 1965 Fanta, 1964, 1974). Copper-induced coupling of vinyl halides has been found to occur with retention of configuration (Cohen and Poeth, 1972). 

Azulene oligomers and polymers are intriguing molecules in terms of tiie construction of functional substances. Some synthetic studies on azulene dimers have been reported. The synthetic methods, however, were considered to restrict the development of further studies. Thus, Ullman coupling reactions at high temperature or some sophisticated reactions based on Hafner s azulene synthesis, starting from bipyridyls, were used. To obtain azulene oligomers, the Suzuki coupling has been applied recently (Equations 10 and 11) [llj. 

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