title: Control of the intramolecular [2+2] photocycloaddition in a bis-stilbene macrocycle.
abstract: The intramolecular [2+2] photocyclization of a bis-stilbene macrocycle was studied. The reaction can be controlled by the insertion and removal of urea protecting groups. Upon UV-irradiation in both the solid state and DMSO solution, the free urea macrocycle undergoes a cis-trans photoisomerization that is followed by a [2+2] cycloaddition to afford a single product in high yield. The presence of the triazinanone urea protecting groups does not alter the cis-trans photoisomerization but greatly decreases the selectivity of the photocycloaddition step.
authors.affiliation: Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA.
authors.forename: Yuewen
authors.initials: Y
authors.lastname: Xu
authors.forename: Mark D
authors.initials: MD
authors.lastname: Smith
authors.forename: Jeanette A
authors.initials: JA
authors.lastname: Krause
authors.forename: Linda S
authors.initials: LS
authors.lastname: Shimizu