67009-89-6Relevant academic research and scientific papers
Generation and Cycloaddition of Cyclopentenylium-2-olate from 2-Chlorocyclopentanone under Alcoholysis Conditions
Froehlisch, Baldur,Joachimi, Roland
, p. 1951 - 1960 (2007/10/02)
2-Chlorocyclopentanone (1a) is solvolysed in basic methanol or 2,2,2-trifluoroethanol to form 2-methoxy- or 2-(2,2,2-trifluoroethoxy)cyclopentanone, respectively (1c,1d).No Favorskii rearrangement is observed.An enolization-ionization mechanism via the oxallyl intermediate 3 is proposed.In competition with the attack by trifluoroethanol the reactive intermediate undergoes cycloadditions with 1,3-butadiene and isoprene to form the bicyclononenones 6a, b.Cyclopentadiene, spiro-hepta-4,6-diene, 6,6-dimethylfulvene, furan, 2-methylfuran, and 2,5-dimethylfuran give the tricycles 7a-f, where the anti stereoisomer (7α) predominates.Products with only one carbon-carbon bound formed (8-11) were observed with isoprene, spiro-hepta-4,6-diene, spironona-1,3-diene, and 2-methylfuran, indicating a two step mechanism of the oxallyl attack by way of the zitterionic intermediates 16a- d.
