SYNTHESIS aryllithium reagents

The most straightforward synthesis of compounds (L)AuAr uses the metathesis of (L)AuX precursors with aryllithium reagents, as, for example, executed for the preparation of (Ph3P)AuPh. The crystal structure of this benchmark complex has been determined. The linear coordination geometry is as expected. No aurophilic contacts are discernible in the crystal packing. Short Au- -Au contacts are observed, however, in the dinuclear compound (dppm)(AuPh)2 with an intramolecular intermetallic distance of 3.154(1) A. This complex shows a UV-VIS absorption at 290-300 nm and is luminescent in fluid solution at room temperature.1... 

Tetravalent phosphorus halides are known to react with lithium reagents, but data is scarce. Aryllithium reagents easily displace chloride ion from phosphoryl chloride in the synthesis of tertiary phosphine oxides (143,144,174). A small quantity of the corresponding phosphinic acid (42) was isolated in the preparation of tris(p-dimethylamino-phenyl)phosphine oxide (43) (174). Choice of conditions and concentrations of reactants may well favor either the single or the double dis-... 

The synthesis of novel perfectly anti-apicophilic phosphoranes (6a-d) was achieved by reacting 1-hydro-5-carbaphosphatrane (4) with an appropriate alkyl- or aryllithium reagent in THF, followed by the hydrolysis and further oxidation of the bicyclic intermediate (5a-d) with iodine (4a and 4b) or by pyrolysis (4c and 4d) (Scheme 2). 

Figure 1.48 A cross-section of results for the Pd-catalyzed synthesis of hindered biaryls using aryllithium reagents as reported by Feringa and coworkers [182].

Biaryl Synthesis with the Hindered Aryllithium Reagent, 2,6-Dimethoxyphenyllithium Catalytic Synthesis of 1,3-Dimethoxy-2-(1-naphthyl)benzene ... 

Jeong et al. also reported on allene synthesis via addition-elimination sequence as a key reaction, starting from 3,3-bis(phenylthio)-l,l,l,2,2-pentafluorobutane 64 (Scheme 26.59). Thus, treatment of 64 with an excess amount of aryllithium reagents in Et20 at low to room temperature for 1-6 hours gives 2-aryl-1,1,1-trilluoro-3-phenylthio-2-butene 65 in 80-96% yields. Bromination of 65 with NBS in MeCN at reflux temperature for 1-7 hours, followed by wCPBA oxidation in CH2CI2 at the reflux temperature for 1-12 hours, results in the formation of 1-aryl-l-trifluoro-methylallenes 66 in 74-96% yields. 

Various commercially available compounds containing C—Li bonds are listed in Table 1. The alkyllithium and aryllithium species listed there are usually very reactive. These compounds serve to prepare in situ other intermediate reagents. These proceedings may afford various advantages in organic synthesis, such as better control of the reaction path, increased stereochemical selectivity and the possibility of working at higher temperatures. 

The use of aryllithium instead of the Grignard reagent resulted in a higher ratio of cis-isomer formation [34], In reaction calorimetric studies, it was found that both steps, the formation of 3-methoxyphenyllithium and its addition to ketone, are pretty exothermic with worst-case temperature rises of up to 62 and 133 °C, respectively. The lithium intermediate has to be kept at very low reaction temperatures to prevent decomposition. We concluded that a continuous reaction may be a good alternative to batch synthesis to improve the reaction yield and to minimize the safety concerns because of the exothermicity of the reaction sequence. 

The cascade sequence that affords bicyclic systems fails with the lithium derivatives of 2-bromo-iV,iV-diallylaniline. The methodology is useful for the synthesis of 3-substituted indolines and indoles, but the substrate undergoes only one anionic cyclization. Alkenyl vinyllithiums and alkenyl aryllithiums have also been employed in the preparation of alkylidenecyclopentanes and indanes. The intramolecular addition of vinyllithium reagents... 

The first chapter discusses the concept of aromaticity, after which there is a description of aromatic substitution reactions. Chapters covering the chemistry of the major functionalized derivatives of benzene follow. A chapter on the use of metals in aromatic chemistry discusses not only the chemistry of Grignard reagents and aryllithium compounds but also the more recent uses of transition metals in the synthesis of aromatic compounds. The penultimate chapter discusses the oxidation and reduction of the benzene ring and the text concludes with the chemistry of some polycyclic compounds. 

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