Treatment of the readily accessible spirocyclohexadienones from the PhI(OCOCF 3 ) 2 -mediated spiro-cyclization of N-substituted benzanilides, with BF 3 ·Et 2 O initiates a tandem ring opening/ closure reaction leading to the formation of the biologically interesting 8-hydroxy-phenanthridin-6(5H)-one compounds. This unique rearrangement pattern involves the 'migration' of the electrondeficient N-methyl carbamoyl moiety rather than the electron-rich aryl group as observed and reported previously in all other similar transformations.
Single-stranded DNA oligonucleotides (ssDNA) are uniquely customizable polymers that are useful for coating, suspending, and structurally sorting single-wall carbon nanotubes (SWCNTs) in water. However, SWCNT dispersions are instead commonly prepared using inexpensive amphiphilic surfactants such as SDS. By monitoring changes in the nanotube fluorescence wavelengths and intensities, we show that such SDS coatings on dispersed SWCNTs can be controllably displaced by the addition of small amounts of ssDNA. The displacement data can be well represented by kinetic modeling, giving the time scales for equilibration of the coating composition. We measured spectra of SWCNT samples that were dispersed in low concentrations of SDS, then treated with small amounts of ssDNA, and allowed to reach equilibrium. Plots of the final spectral shifts as a function of added ssDNA provide (n,m)-specific “titration” curves that show strongly diameter-dependent behavior. Smaller diameter nanotubes undergo SDS displacement at the lowest ssDNA concentrations. The limiting spectral shifts suggest that SWCNT surfaces become coated with adsorbed SDS as well as ssDNA. We will illustrate how the (n,m)-dependent displacements found here can be used for structural sorting of mixed SWCNT samples.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.