Ullman-type Couplings

Ullman type coupling occurs between aryl halides and trifluoromethyl copper species generated by the action of copper iodide on sodium tnfluoroacetate [168, 169] or on methyl fluorosulfonyldifluoroacetate [170] (equation 145) Similarly the pentafluoroethyl group can be introduced from potassium pentafluoropropion-ate [171] (equation 146)... 

A potentially profitable discovery was that dibromide 74 will undergo an Ullman-type coupling to give the corresponding bis(l,2,4-triazole) 76 in 51% the reaction conditions employed were chosen in order that a trifluoromethyl substituent could be introduced but this reaction did not occur, the biaryl bond formation being preferred (Equation 27) <2006T3301 >. 

The copper-catalysed, Ullman-type coupling of aryl, heteroaryl and alkenyl halides may be achieved at ambient temperature using copper(I) thiophene-2-carboxylate as catalyst.60 A new semiconducting poly(anthraquinone-l,5-diyl) with nitro groups at the 4- and 8-positions has been prepared by Ullman-type coupling using metallic copper or a zerovalent nickel complex as catalyst.61... 

The Ullman-type coupling of 3-pyridylcopper with aryl iodides has been reported yields are improved when the arylcopper is stabilized by the addition of an equivalent of triphenylphosphine (equation 53)75. 

The applications of microwave chemistry to organic chemistry are too numerous to mention. A few representative examples will be given to illustrate the scope and utility. Microwave chemistry is widely used in synthesis. Examples include the Heck reaction (reaction 13-10)," the Suzuki reaction (reaction 13-12)," the Sonogashira reaction (reaction 13-13)," Ullman type couplings (reaction... 

In Ullman-type coupling, aryl boronic acids are much more efficient coupling partners with amines and phenols as compared with aryl halides. They successfully couple at room temperature in the presence of a copper acetate/triethylamine (or pyridine) catalyst system and the corresponding arylated products were provided in high yields (Scheme 15.20). Similarly, aryl boronic acids are successfully coupled with structurally and electronically diverse substrates such as amides and sulfonamides to afford the corresponding IV-arylated products. 

In the top left case, a palladium-catalysed nitrile coupling was rapidly executed by 2 min of microwave irradiation, while the phenyl-imidazole moiety was created using a very slnggish Ullman-type of reaction. 

Direct coupling of vinyl halides and phenols under Ullman-type reaction conditions can be useful for the preparation of aryl vinyl ethers, and intramolecular version of this process has been applied to the synthesis of spirocyclic oxindoles through a sequence of intramolecular Ullman coupling and Claisen rearrangement reactions (eq 58). ... 

We next turned our attention to utilization of 2-fluoro-4-iodoaniline (15), hoping to displace the iodide with methoxide under Ullman-type conditions.(77) Literature precedent for effecting this type of coupling on the free aniline... 

Organocopper intermediates are involved in another broad class of reactions which accomplish the coupling of two organic substrates. The classical example of this type of reaction is the Ullman coupling of aryl halides, which is usually done with a copper-bronze alloy. Good yields in this reaction are limited to halides with electron-attracting substituents. Mechanistic and synthetic work has revealed the... 

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