Establishing linear-free-energy relationships for the quadricyclane-to-norbornadiene reaction

Manso, Mads, 1991 (author): Köpenhamns universitet,University of Copenhagen,Chalmers tekniska högskola,Chalmers University of Technology

Petersen, Anne Ugleholdt (author): Köpenhamns universitet,University of Copenhagen

Moth-Poulsen, Kasper, 1978 (author): Chalmers tekniska högskola,Chalmers University of Technology

Nielsen, Mogens Brondsted (author): Köpenhamns universitet,University of Copenhagen

(creator_code:org_t)

2020
2020
English.
In: Organic and Biomolecular Chemistry. - : Royal Society of Chemistry (RSC). - 1477-0539 .- 1477-0520. ; 18:11, s. 2113-2119

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Abstract Subject headings

The kinetics of the thermal quadricyclane-to-norbornadiene (QC-to-NBD) isomerization reaction was studied for a large selection of derivatives where the one NBD double bond contains a cyano and aryl substituent of either electron-withdrawing or -donating character. While the kinetics data did not satisfy a linear-free-energy-relationship for all the derivatives based on Hammett sigma values, we found individual linear relationships for derivatives containing either electron-withdrawing or electron-donating para substituents on the aryl group; with the most electron-witdrawing substituent in the one series and with the most electron-donating substituent in the other providing the fastest reaction (corresponding to opposite slopes of the Hammett plots). All data were well described, however, by a linear relationship when using Creary radical values; the correlation could be slightly improved by using a combination of sigma and values (used in ratio of 0.104 : 1). The results imply a combination of polar and free radical effects for the isomerization reaction of this specific class of derivatives, with the latter playing the most significant role. The NBD derivatives were prepared by Diels-Alder cycloaddition reactions between cyclopentadiene and 3-arylpropiolonitriles, and in the case of bromophenyl derivatives further cyanation and Sonogashira coupling reactions were performed.

By the author/editor: Manso, Mads, 199 ...; Petersen, Anne U ...; Moth-Poulsen, Ka ...; Nielsen, Mogens ...

About the subject

NATURAL SCIENCES: NATURAL SCIENCES; and Chemical Science ...; and Inorganic Chemis ...

NATURAL SCIENCES: NATURAL SCIENCES; and Chemical Science ...; and Theoretical Chem ...

NATURAL SCIENCES: NATURAL SCIENCES; and Chemical Science ...; and Organic Chemistr ...

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