Organometallic Tautomerism and Dual Reactivity

We (Nesmeyanov, Freidlina, Borisov) had discovered dual reactivity when studying the behavior of the adducts formed from mercury salts and unsaturated compounds, especially acetylene. The adducts reacted both as complexes and as chlorovinyl metal compounds. As previously mentioned, dual reactivity was explained by a,CT-conjugation. Later we [Nesmeyanov, Lutsenko (77, 78), Perevalova (79)] found that the CT,77-conjugation was of no less significance. Vinylic ethers or esters treated with mercury 

Similar reactions occur with a-chloromercury ketones. Reactions of type (a) are less representative than those of type (b) acyl chlorides, aryl sulfonyl chlorides, and dialkylchlorophosphites react according to type (b) and display reaction site transfer. Is this a result of keto-enol tautomerism ( mercurotropy ) Can metallotropic tautomerism occur Or, alternatively, can the ambivalent behavior be explained by reaction site transfer, which in this case involves the a, 77-conjugated system  

Thus a-C-organometallic derivatives of 0x0 compounds are, as a rule, acylated or alkylated at the oxygen atom, the reaction site being transferred as in the scheme 

as with all conjugated systems, as well as the quasi-complex compounds, the 1,4-attack takes place so that the 3,4 a- and the 1,2 77-bonds are broken, while the 2,3 77-bond is formed. The process very probably involves a six-membered transition state. A four-membered state may participate in C-alkylation where the reaction site is not transferred. 

and many other results (80-88), led us to the problem of the dual reactivity of metal enolates. We prepared (89) the simplest enolates such as CH2=CHOLi and CH2=CHONa by reacting the mercury derivative of acetaldehyde with the respective metal. 

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