title: Vinyl benzenes as dienes in mild solid-phase Diels-Alder reactions
abstract: Wang resin-bound intermediates derived from Fmoc-L-phenylalaninal and Fmoc-L-valinal, and a resin supported Horner-Wadsworth-Emmons reaction, were treated with cinnamaldehyde derivatives, acetic acid, and borohydride to give secondary amines which were subsequently benzoylated to afford various derivatives of 3. Heating 3 at 95 degrees C induced cycloaddition reactions and produced 4 as the major product. Compounds 3 which were derived from 4-methoxycinnamaldehyde were more reactive, but did not give 4 and 4-7g. The direct cleavage of 3b using TFA led to the isolation of cycloaddition-demethylation product 10. The derivative of 3, which contained an electron-withdrawing nitro group on the phenyl ring, produced a single diastereomer of 4. The Diels-Alder cycloaddition between two electron-deficient counterparts showed similar reactivity to that of the reactions which have a normal complementary electron-demand.
authors.affiliation: R.W. Johnson Pharmaceutical Research Institute, Raritan, New Jersey 08869, USA.
authors.initials: S
authors.lastname: Sun
authors.initials: IJ
authors.lastname: Turchi
authors.initials: D
authors.lastname: Xu
authors.initials: WV
authors.lastname: Murray