The Kocheshkov Reaction

The reactivity follows the sequence R = phenyl benzyl vinyl methyl ethyl higher alkyl, and X = Cl Br I. When R = alkyl and X = halide, the first stage of the reaction (equation 11-3) takes place rapidly at room temperature. 

With a 1 3 ratio of reagents, R3S11CI is formed in good yield when R is aryl or a straight-chain alkyl group, but yields are sometimes low for branched-chain alkyl homo-logues. Tributyltin chloride and triphenyltin chloride are prepared commercially by this reaction. 

When R Me, heating, usually to about 200 °C, is needed to induce the next stage of the reaction  

Thus when liu4Sn and SnCI4 are heated at 240 °C for 3 h, BuaSnCB is formed in 95% yield,10 but again yields can be low if R is a branched alkyl group. Dibutyltin dichloride and dioctyltin dichloride are prepared in this way commercially. 

The low reactivity of the cyclohexyl-tin bond has been exploited in preparing the spacer bridged bistrichlorides, Cl3SnSpSnCl3 (Sp = alkylene, arylene, or aryl-dimethylene) by the Kocheshkov reaction of Cy3SnSpSnCy3 with S11CL4.12 From these hexachlorides, a variety of compounds R3SnSpSnR3 (e.g. R = MeOC) can be prepared. 

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Of this research, I will mention here only aminoferrocene. We were very glad to obtain the compound through the Kocheshkov reaction of ferrocenyllithium and hydroxylamine 0-ether [Nesmeyanov, Perevalova, Shilovtseva 260)] later, we synthesized aminoferrocene via other paths 261, 262). 

The metal M is commonly magnesium in a Grignard reagent, or lithium, or aluminium, and X is commonly halide. Selective partial alkylation of the tin is usually difficult to achieve, and the reaction is taken to completion to give R4Sn (equation 4-8) if any organotin halides are present, they can be removed as the complexes which they form with dry ammonia, or as the insoluble fluorides which they form with sodium fluoride. Any subsequent dealkylation, if required, can then be achieved by the Kocheshkov reaction (Section 11.1.2). 

Reactions of organotin compounds with Lewis acids by have been carried out particularly with mercury(II) salts in mechanistic studies, with SnCl4 (the Kocheshkov reaction) for the preparation of alkyltin chlorides, and with lead tetraacetate. 

The Kocheshkov reactions are discussed in Section 11.1.2 on organotin halides. 

Allyltin halides are formed by the Kocheshkov reaction, and have also been obtained by the retro-ene elimination of a ketone from a homoallyloxystannane.24... 

Erotic reagents (e.g. equation 9-49) and other electrophiles (e.g. halogens) readily cleave the Cp-Sn bond, and the Kocheshkov reaction with SnCL occurs rapidly even at... 

Some examples of the Kocheshkov reaction are given in Table 11-1. 

Table 11-1 Organotin halides prepared by the Kocheshkov reaction.

The most widely utilized reaction of tetraorganotins is the Kocheshkov redistribution reaction, by which the tri-, di-, and in some cases the monoorganotin hahdes can be readily prepared ... 

The production of triphenyl tin hydroxide [76-87-9] and triphenyl tin acetate [900-95-8] start with triphenyl tin chloride, which is prepared by the Kocheshkov redistribution reaction from tetraphenyltin and tin tetrachloride. The hydroxide is prepared from the chloride by hydrolysis with aqueous sodium hydroxide. The acetate can be made directiy from the chloride using sodium acetate or from the hydroxide by neutrali2ation with a stoichiometric quantity of acetic acid. 

Allyltin chlorides, allylSnIL/T-, are more reactive in carbonyl addition than are the allyltrialkylstannanes, allylSnRj, and for this purpose, the latter can be converted into the former by the Kocheshkov redistribution reaction with BuSnCl3 or S11CI4 the /ra r-stannylation can be carried out with the carbonyl compound in situ in a one-pot process (Equation (97)).270... 

Organotin halides are commonly prepared by the Kocheshkov redistribution reaction, where an organic group on tin (e.g., in SnR4) exchanges (reversibly) with a halide group on tin (e.g., in SnCLt).64 Two recent examples are shown in Equations (125) and (126). The first reaction exploits the high reactivity of the Sn-Me bonds, and the second... 

In 1958, Panov and Kocheshkov found another route to the formation of the C—Pb bond, namely the interaction of tetraacyloxyplumbanes with aromatic and heteroaromatic compounds (the plumbylation reaction). They showed that the reaction of thiophene with Pb(OCOPr-i)4 at room temperature during 10 days led to unstable RPb(OCOR )3 (R = 2-thienyl R = i-Pr), which was disproportionated to R2Pb(OCOR )2 and Pb(OCOR )4. 

The Kocheshkov redistribution reaction between tetra-organotins and tin(rV) halides, in appropriate mole ratios, is a general method of synthesis of organotin halides (equations 59 and 60). It is a particularly useful reaction, since it is difficult to control the alkylation of SnX4 by organolithium or Grignard reagents to the desired extent. 

Allylstannanes rapidly undergo the Kocheshkov comproportionation reaction with SnCU, even at -50 °C. The initial product is apparently formed with allylic inversion, but further transmetallation may give other allylic isomers.35 The SnCl3 group which is formed enhances the electrophilic power of the allyl group. This has been exploited in aromatic allylation (equation 9-13),36 and transmetallations of this type provide the basis for some, but not all, of the examples of the catalysis of the allylation of carbonyl compounds by allylstannanes in the presence of Lewis acids37,38 (Section 9.1.3.4). 

Scheme 1.1.1 Synthesis of organotin(fV) compounds based on alkylation of SnCU with an organometallic reagenf and the Kocheshkov redistribution reaction...

The reactant compounds, namely, dibutyltin dichloride and dioctyltin dichloride, are commercially produced by the Kocheshkov disproportionation reaction whereby Bu4Sn (or OC4 Sn) is heated with SnCLt at about 240°C for several hours. ... 

Chemical Properties. The most impoitant reactions which tetraorganotins undergo are heterolytic, ie, electrophilic and nucleophilic, cleavage and Kocheshkov redistribution (81—84). The tin—carbon bond in tetraorganotins is easily cleaved by halogens, hydrogen hahdes, and mineral acids ... 

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