Organolithium compounds nucleophilic addition

A further synthetic approach to carbon-metal double bonds is based on the acid-catalyzed abstraction of alkoxy groups from a-alkoxyalkyl complexes [436 -439] (Figure 3.11). These carbene complex precursors can be prepared from alk-oxycarbene complexes (Fischer-type carbene complexes) either by reduction with borohydrides or alanates [23,55,63,104,439-445] or by addition of organolithium compounds (nucleophilic addition to the carbene carbon atom) [391,446-452]. 

Addition of Grignard reagents and organolithium compounds to the pyridazine ring proceeds as a nucleophilic attack at one of the electron-deficient positions to give initially... 

The most important application of organolithium reagents is their nucleophilic addition to carbonyl compounds. One of the simplest cases would be the reaction with the molecule CO itself, whose products are stable at room temperature. Recently, it was shown that a variety of RLi species are able to react with CO or f-BuNC in a newly developed liquid xenon (LXe) cell . LXe was used as reaction medium because it suppresses electron-transfer reactions, which are known to complicate the reaction . In this way the carbonyllithium and acyllithium compounds, as well as the corresponding isolobal isonitrile products, could be characterised by IR spectroscopy for the first time. 

If we look for elements which enable a C-C double bond to add organolithium compounds, normal nucleophilic addition or cycloaddition according Scheme 53, we are restricted to the lighter elements (Scheme 54 A) because only these are resistent... 

The preparation of organolithium compounds and of Grignard reagents from halides is successful only when these reagents contain virtually no functional groups. Furthermore, these C nucleophiles can be added to the C=0 double bond of a carbonyl compound only when this carbonyl compound also contains practically no additional electrophilic group(s). 

A few isolated examples104 172 187 147 prior to 1998 showed that organolithiums 427 tethered to aromatic rings can on occasion cyclise, apparently by nucleophilic addition of the organolithium to the Ti-system of the aromatic ring. In some cases (for example, the conversion of 194 to 196 or 298 to 299),104147 the organolithium 428 rearomatises to yield a new benzo-fused compound 429 in others (for example, conversion of 374 to 376, or 431 to 432 below),172 187 protonation yields a stable, dearomatised bicyclic product 430 or an isomer. 

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