Organosodium species

The Wurtz reaction, which reties on in situ formation of an active organosodium species, is also usefiil for preparing tetraorganotin compounds and is practiced commercially. Yields are usually only fair and a variety of by-products, including ditins, also form ... 

The mechanism of the Wurtz coupling is not well understood, and the currently accepted mechanism involves two steps 1) formation of a carbanionic organosodium compound via metal-halogen exchange and 2) the displacement of the halide ion by the organosodium species in an Sn2 reaction. Alternatively, a radical process can also be envisioned, although to date there has been no experimental evidence to support this assumption. 

A related [l,2]-rearrangement was described by Schlenk and Bergman in 1928. As shown below, reduction of benzophenone dimethyl acetal (6) with metallic sodium led to the formation of diphenyl methyl carbinol (8), presumably via intermediate organosodium species 7. ... 

This report covers the use of chelated organosodium compounds as novel catalysts for telomerizing conjugated diolefins with weak hydrocarbon acids such as aromatics and olefins (7). The factors affecting the chain-transfer reaction were of particular interest because one of our objectives was to increase selectivity to low-molecular-weight species. The products are useful in synthesizing plasticizer alcohols, flame retardants, and surface coatings. 

In our previous discussion it was pointed out that 4-chloro-l-p-biphenylyl-l,l-diphenylbutane reacts with Cs-K-Na alloy in THF at -75°C to give only rearranged product 58 (see Scheme 7) in a reaction time as short as 2 minutes. In view of the known stability of species such as 67 and 68 is it reasonable to write the spiro anion 57 as an intermediate in this reaction Probably this question should be answered in the affirmative on the basis that we have been able to prepare (25, 26) the closely related anion 70 in 76% yield by reaction between 4-chloro-l-p-biphenylylbutane and Cs-K-Na alloy in THF at -70°C (see Scheme 9). The same spiro anion may also be prepared, but only in some 22% yield, by reaction between the chloride and cesium or potassium metal in THF at 65°C. Experiments with sodium and potassium, in which dioxane or tertiary alcohols in THF were used as a proton source to trap intermediate anions, indicate that 4-p-biphenylylbutyl anion (69) is a preeursor of 70 (see Seheme 9). The organosodium intermediate 69 (M+ = Na ) in dioxane at 101°C gave primarily 1-p-biphenylylbutane... 

One important class of anionic-polymerization initiators are the organometallic compounds, especially those of lithium and sodium (see Chapter 5 to review the general properties of the metalloalkyls). Grignard reagents can induce polymerization of acrylonitrile and acrylate esters, but not of hydrocarbons. Initiation by organosodium compounds often involves in situ generation of the active species from sodium metal. Sodium metal catalyzes the polymerization of dienes, and the mechanism has been shown to involve a dianion formed by dimerization of the diene radical anion. An alternative initiation system for anionic polymerization involves... 

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