74503-37-0Relevant academic research and scientific papers
a(E)-1-methoxy-1,3-butadiene and 1,1-dimethoxy-1,3-butadiene in (4+2) cycloadditions. A mechanistic comparison
Sustmann,Tappanchai,Bandmann
, p. 12555 - 12561 (2007/10/03)
The reactions Of (E)-1-methoxy-1,3-butadiene (1) and 1,1-dimethoxy-1,3-butadiene (2) with a series of dienophiles of increasing electrophilicity are described. Stereochemical studies reveal that the cycloadditions of 1 are concerted processes, even for the most electron-deficient olefins dimethyl dicyanofumarate and dimethyl dicyanomaleate. 1,1-Dimethoxy-1,3-butadiene reacts under our conditions (dilute solutions and temperatures ≤60°C) only with those dienophiles which can give zwitterions out of the antiperiplanar conformation of the diene. Zwitterionic intermediates can be trapped by methanol. In the case of tetracyanoethene the kinetics of decay of an intermediate, interpreted as the zwitterion, can be followed by stopped flow techniques: E(a) = 14.8 ± 0.2 kcal mol-1, log A = 11.9 ± 0.1, ΔH(≠) = 10.8 ± 0.1 kcal mol-1, ΔS(≠) = -6.2 ± 0.1 cal mol-1 K-1, and ΔG(≠) = 11.40 ± 0.03 kcal mol-1.
Reaktivity of Substituted 1,3-Butadienes in Diels-Alder-Reactions
Ruecker, Christa,Lang, Dietrich,Sauer, Juergen,Friege, Henning,Sustmann, Reiner
, p. 1663 - 1690 (2007/10/02)
Kinetic data for the reaction of substituted 1,3-dienes with tetracyanoethylene (TCNE) and other dienophiles are interpreted in terms of the FMO-model.While the expectations are fulfilled qualitatively, the kinetic data cannot be correlated quantitatively.This shows that in Diels-Alder reactions besides HOMO-LUMO separation other factors play an important role, for instance the 1,4-distance in the diene and the conformational equilibrium cisoid transoid of the diene.The kinetic data are in accord with a one-step mechanism of the cycloaddition reaction.
