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Alkylation of 3,4-Dibromo-4-methyltetrahydropyran with Diethyl Malonate as a Key to Understanding the Electronic Nature of Chemo- and Regioselectivity of Molecules

“…First, we have succeeded in findings arguments in support of the possibility of the presumed effect and, second, we have succeeded in demonstrating that this effect results from the well-known intramolecular donoracceptor interaction [8,1113] which in the given case occurs between the sodium cation and carbonyl oxygen atom of enolate VII (intramolecular interaction c). Analogous influence (reduction of the acceptor power of, e.g., aluminum atom in alanes) is observed even in going from a solution in benzene to more basic diethyl ether [18,29]. This effect is so strong that it leads to complete inversion of stereoselectivity in the addition of alane at the carbonyl group (88 : 12 against 17 : 83).…”

“…In the framework of this version, the positive charge on the sodium atom in an alkoxide group and therefore its ability to favor heterolytic dissociation increase rather than decrease within a homologous series. This information is usually revealed starting from determination of local polarity which, according to the electronegativities of atoms [17,18,27,28], is induced by hydrogen and oxygen atoms on each carbon atom of the alkoxide group. It is assumed that the induced polarity (charges on atoms are expressed in c.b.i.c.…”

“…In this respect, the most important information is obtained from the statement that a chemical reaction occurs only when the affinity of a reagent exceeds the force preventing rupture of the electrofugenucleofuge bond in a substrate [32]. Otherwise, the interaction stops at the stage of formation of a metastable donoracceptor complex like DAC-IA which occurs in equilibrium with the initial reactants.…”