Nucleophylic attack

It is interesting that the cleavage of the imidazolone ring occurs non-enzymically by a nucleophylic attack of OH at C-2 whereas the enzymic cleavage, also by a nucleophylic attack, occurs at C-4. 

The palladium -assisted nucleophylic attack on a coordinated olefin studied by ab-initio semiquantitative method is presented in Fig. 17.5. 

A concerted mechanism assuming the elecrophylic attack of one oxygen atom of the diiron ferryl to the C-H bond carbon with nucleophylic assistance of the second oxygen atom with the formation of a pentavalent carbon intermediate (Shteinman, 1996). 

In order, to direct these reactions to the desirable rearrangement course, they were carried out in solvents, which did not have a nucleophylic centre, to prevent the attack on to the intermediate carbonium ion obtained during the reaction. As the solvent, we chose dry benzene. It turned out that in benzene in the presence of HgSO, the reaction does not proceed, while in the case of CICH COOH as a catalyst, the reaction follows two courses - two new substances - the product of rearrangement of FK-IG were isolated - unsaturated ketone V (as a main product - 60% yield) and the product of intermolecular dehydratation - VI (with insignificant amount). A part of reactionary mass is gummed ... 

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