Carbon‐14‐labeled 2,3,7,8‐ and 1,2,7,8‐tetrachlorodibenzofuran

Abstract

Both 2,3,7,8-and 1,2,7,8-t e t r a c h l o r o d i benzofuran -U14C, s p e c i f i c a c t i v i t y 57 mCi/mol, have been obtained i n low y i e l d b u t a t > 98% p u r i t y Pschorr c y c l i z a t i o n o f 2-phenoxyanil i n e -U14C, c h l o r i n a t i o n of t h e r e s u l t a n t dibenzofuran and separation o f t h e t e t r a c h l o r o isomers by hplc. The lower y i e l d s obtained i n t h e Pschorr c y c l i z a t i o n o f "hot" 2-phenoxyaniline i n comparison w i t h t h e " c o l d " m a t e r i a l are postulated t o r e s u l t from enhanced homolytic r e l a t i v e t o h e t e r o l y t i c cleavage o f t h e "hot" diazonium i o n leading t o a "hot" f r e e r a d i c a l which polymerizes. The completely anomalous r e s u l t s observed i n the attempted palladium acetate-mediated c y c l i z a t i o n o f diphenyl e t h e r -U14C are l i k e w i s e i n t e r p r e t e d i n terms o f t h e i n t e r v e n t i o n o f a " h o t " f r e e r a d i c a l .

Toward the Design of Molecular Chameleons: Flexible Shielding of an Amide Bond Enhances Macrocycle Cell Permeability

“…As the mixtures were difficult to purify, they were oxidized by IBX − at 85 °C, which provided 8a – e in 12–25% yields. At this stage, the byproduct of the deamination-diazotization reaction sequence of 7c was identified as resulting from an oxidative coupling − between the ortho positions of the ether-linked phenyl residues to give 9 (14%). Similar side products were obtained from 7a , 7b , 7d , and 7e , but they were not isolated and characterized.…”