Observation by flow (sup 1)H NMR and dimerization kinetics and products of reactive ortho-quinodimethanes and benzocyclobutadiene.

摘要

The reactive o-quinodimethanes, 1,2-dimethylene-1,2-dihydronaphthalene (9) and o-xylylene (1) were observed by flow (sup 1)H NMR spectroscopy at room temperature. The (sup 1)H NMR spectrum of 9 was obtained in the absence of precursor and dimers. However, the (sup 1)H NMR spectrum of the more reactive 1, generated in a similar manner from (o-((trimethylsilyl)methyl)benzyl)trimethylammonium iodide (5.) could be obtained only in the presence of its stable (4 + 2) and (4 + 4) dimers. The dimerization kinetics of 3-methyl- (5(prime)), 3,6-dimethyl- (11), 3-isopropyl- (12), and 3,6-diisoproply-1,2-xylylene (13) in acetonitrile (CH(sub 3)CN) were studied by stopped-flow UV-visible spectroscopy. Fluoride ion induced 1,2-elimination from 2-elimination from 2-trimethylsilylbenzocyclobutenyl-1 mesylate (26) was used to generate the reactive molecule benzocyclobutadiene (1(prime)) in CD(sub 3)CN, which was observed by flow (sup 1)H NMR spectroscopy at room temperature. The (sup 1)H NMR spectrum (in CD(sub 3)CN) of 1,2-dimethylene-1,2-dihydrothiophene (1(double prime)), obtained by fluoride ion induced 1,4-elimination from 3-(trimethylammoniummethyl)-2-(trimethylsilylmethyl)thiophene iodine was observed by flow (sup 1)H NMR spectroscopy at room temperature. The dimerization rate of 1(double prime) in CH(sub 3)CN, generated in the same manner, was measured by UV-visible spectroscopy. 166 refs., 7 figs., 7 tabs.