Ullmann type reactions

N-arylation has been used as the first step in several syntheses of complex molecules. The Ullmann-type reaction of 2-iodo-3-methoxybenzoic acid with l-methylpiperazine-2,5-dione forms the basis of Kishi s total synthesis of dehydrogliotoxin (81T2045) (Scheme 12). 

If aryl iodides, sodium cyanide and copper(I) iodide are used, a simple mechanism similar to that of an Ullmann-type reaction can be proposed ... 

There are two different transformations referred as the Ullmann Reaction. The classic Ullmann Reaction is the synthesis of symmetric biaryls via copper-catalyzed coupling, the Ullmann-type Reactions include copper-catalyzed Nucleophilic Aromatic... 

Ullmann-type reactions proceed through a catalytic cycle, and in one mechanism the copper is postulated to undergo oxidation to Cu(III). As some Gu(IIl) salts have been prepared. 

The Ullmann-type reaction that is homocoupling of aryl or vinyl halides is conveniently mediated by copper at high temperature. The copper powder serves as a zerovalent metal. The classical Ullmann reaction reported in 1901 has long been employed by chemists to generate a carbon-carbon bond between two aromatic nuclei. 

The Falk procedure (Scheme 3.2.2), in contrast to the Sessler-Vogel one, relies on an Ullmann-type reaction using a dibromo or diiodo tetrapyrrolic precursor (e.g., 3.138-3.141) in its key, macrocycle-forming step. In accord with this general strategy, these workers found that heating the dibromo tetrapyrrole 3.138, or the... 

V-Alkylated analogues 19b-d (see Scheme 4.5) were prepared using a modified procedure. To this end, sulfenyl diaryl ether 27 was prepared from phenol and 26 using an Ullmann-type reaction [26], and was then oxidized to sulfoxide 28. Lithiation and... 

The required perfluorinated phospane ligand can easily be prepared in three steps starting from 4-iodoaniline. The fluorinated chain was introduced via an Ullmann-type reaction with F13C6I in presence of copper-bronze in DMSO at 120°C for 1 h leading to the perfluoroalkyl substituted aniline 35 in 86% yield... 

C (Scheme 9.7) [70]. This represents the lowest reaction temperature for an Ullmann-type reaction to date. The corresponding coupling products were obtained in good yields and excellent enantioselectivity using Cul/trans-4-OH-L-proline (L3). 

Similar variants of Ullmann-type reactions based on intra- as well as intermolecular homo-couplings of various arylmetallic reagents, beside aryllithiums, also aryl Grignard reagents, arylzincs etc. with copper(II) salts give intermediate diarylcopper(Il) reagents which subsequently produce respective biaryls, usually in good yields, see Chapter 7. 

Transition metal-catalyzed esterification, includinglactonization 12SL357. Copper-catalyzed reactions of diazo compounds 12CC10162. Synthetic developments and applications of Ullmann-type reactions (formation of C—O, C—N, or C—S bonds) 130PP341. 

The Ullmann reaction can be taken to refer to two different transformations. The first is the copper mediated coupling of two aryl groups to give a biaryl compound this is the classic Ullmann reaction. The second, the Ullmann-type reaction, is the nucleophilic aromatic substitution between aryl nucleophiles and aryl halides, the most common of which is the Ullmann ether synthesis. The classic Ullmann reaction will be reviewed in this chapter the reader is refered to several excellent reviews for details on the Ullmann-type reaction. " ... 

Sodium mercaptides are prepared from the mercaptans and aqueous or alcoholic solutions of sodium hydroxide or alcoholic sodium eth-oxide. The sodium mercaptide reacts with halides, chlorohydrins, esters of sulfonic acid, or alkyl sulfonates [6] to give sulfides in yields of 70% or more. A recent report describes a general procedure for synthesizing aryl thioesters by a nucleophilic displacement of aryl halide with thiolate ion in amide solvents. No copper catalysis is necessary as in an Ullmann-type reaction. 

By far the greatest number of reports on the modem catalytic Ullmann-type reactions has dealt with the creation of C-N bonds. Amongst the numerous pubhcations 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. 

Amino acids, especially L-proline L6 and AA -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 mUd 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. 

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