Organocuprates reaction with alkyl tosylates

Thermolysis of 4-tosyloxybutyl trimethyltin stops at the stage of but-3-enyl-trimethyltin if base (2,6-lutidine) is present, but in the absence of the latter a mixture of methylcyclopropanes, but-l-ene, and other decomposition products is obtained. Posner and Ting have demonstrated that in the alkylation of allylcarbinyl tosylates with organocuprates, reaction does not always take place by oxidative addition-elimination at the copper, and in certain instances the double bond of the ethylenic tosylate can take part in the substitution, with resultant formation of the cyclopropylalkane. 

All of these reactions are illustrative of the very powerful nucleophilicity that organocuprates exhibit toward carbon. The reactions are generally considered to proceed by direct displacement on the substrate. Secondary tosylates react with inversion of stereochemistry, as is the case for classical Sn2 reactions. " The overall mechanism probably consists of two steps. First an oxidative addition to the metal in which the copper acts as a nucleophile. This is followed by migration of one of the alkyl groups from copper. This kind of process is well documented by mechanistic studies with other types of organometallic compounds. 

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