In an effort to remove residual palladium from a drug
candidate
prepared by palladium-catalyzed indolization, many
treatments
were examined. The most effective treatment was to
precipitate
palladium from solution using
2,4,6-trimercapto-s-triazine
(TMT), which reduced palladium levels from 600−650 ppm
to
20−60 ppm in an isolated indole intermediate.
Subsequent
crystallizations routinely afforded active pharmaceutical
ingredient with <1 ppm of palladium. TMT treatment
should
prove useful to reduce the concentration of residual
palladium
in other reactions.
A new class of oxaziridine derivatives, 2-arenesulfonyl-3-aryloxaziridines (2), is prepared by m-CPBA oxidation of sulfonimines (RSOlN=CHAr). These compounds are the first stable examples of this ring system to have a substituent other than carbon attached to nitrogen and are characterized by a highly electrophilic oxaziridine oxygen atom. These oxaziridines have the E configuration as determined by X-ray crystallography. The presence of the powerful electron-attracting sulfonyl group attached to nitrogen apparently has little effect on the structure of the oxaziridine three-membered ring. Of more significance are the observations that the nitrogen lone pair in 2 is opposite to one of the sulfonyl oxygens and that the long S-N bond length implies little if any conjugative interaction between sulfur and nitrogen. Attempts to prepare oxaziridines via oxidation of sulfonimines, 5, derived from acetophenone gave imidoyl ether 14, a novel Baeyer-Villiger oxidation product of a C-N double bond.Three-membered heterocyclic compounds are important synthetic reagents and have played key roles in elucidating the fundamental properties of organic molecules. Unique members of this class of heterocycles are the oxaziridines, compounds containing 0, N , and C atoms in a three-membered ring.Oxaziridines, in general, are highly reactive molecules that display novel and unusual chemistry.2 At present an understanding of the reactions and properties of these compounds, particularly from a mechanistic standpoint, remains undefined.3 Furthermore, the synthetic potential of oxaziridines has yet to be realized.
2-Arenesulfonly-3-aryloxaziridines (2) are a new class of oxaziridines prepared by oxidation of the corresponding sulfonimine, 1, according to eq 1 .4 These compounds are the first A r c 111 m -C P B A NaHCO1-HzO CWCl3
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.