Exchange with Other Organometallics

C. Alkyl-Zn Exchange with Other Organometallic Compounds. 211... 

Organo-Zn, -Cd and -Hg derivatives can be prepared from other compounds by proton-metal exchange with acidic hydrocarbons by olefin insertion and by metal-metal exchange with other organometallics. In all cases alkyl groups are substituted by other... 

S.7.2.4.3. by Metal-Metal Exchange with Other Organometallics. 

Group-IA organometallics can react with other organometallics in a metal-metal exchange ... 

There are a wide variety of methods for introduction of substituents at C3. Since this is the preferred site for electrophilic substitution, direct alkylation and acylation procedures are often effective. Even mild electrophiles such as alkenes with EW substituents can react at the 3-position of the indole ring. Techniques for preparation of 3-lithioindoles, usually by halogen-metal exchange, have been developed and this provides access not only to the lithium reagents but also to other organometallic reagents derived from them. The 3-position is also reactive toward electrophilic mercuration. 

The bimetallic mechanism is illustrated in Fig. 7.13b the bimetallic active center is the distinguishing feature of this mechanism. The precise distribution of halides and alkyls is not spelled out because of the exchanges described by reaction (7.Q). An alkyl bridge is assumed based on observations of other organometallic compounds. The pi coordination of the olefin with the titanium is followed by insertion of the monomer into the bridge to propagate the reaction. 

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