Synthesis of specific polychlorinated dibenzofurans

Abstract

Comments on Standardization of Chemical Shift Values. In our previous report on the 1H NMR spectra of several of these bicyclic adducts,2 i.e., 18a and 18c, in addition to incorrect assignment of the protons H1-H4, we had some difficulty due to nonlinearity of the field on the C-60 HL. This problem was corrected and standards of known chemical shift were used to calibrate all spectra reported here.

Exhaustive hydrodechlorination of chlorinated aromatic environmental pollutants to alicyclic compounds

“…In this experiment (Table 2, entry 4) chlorine-free bicyclohexyl was obtained in quantitative yield. Using 1,2,4-trichlorodibenzo[b,e][1,4]dioxin 13 and chlorinated dibenzofuran 14 as model compounds, for polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) the high efficiency of our catalyst was demonstrated again through exhaustive hydrogenation of these compounds (entries 5 and 6). While the dioxin derivative yielded almost entirely pure dodecahydrodibenzo[b,e][1,4]dioxin, 15 the dodecahydrodibenzofuran 16 was contaminated with up to 18% of a mixture of chlorine-and oxygen-free non-aromatic hydrocarbons.…”

2,3,7,8-Tetrachlorodibenzofuran

“…1) and tables of this paper is shown as 3,4,3',4'-tetrachlorodibenzofuran. extremely active biologically (see Discussion for references). This specific tetrachloro isomer was synthesized under an FDA-supported contract by Gray, Dipinto & Solomon (1976). Crystals of the compound suitable for structural analysis were crystallized from 2,2,4-trimethylpentane ('iso-octane'; distilled in glass) by one of us (IHP) and dried with paraffin under vacuum.…”

Synthesis of possible metabolites of 2,3,7,8-tetrachlorodibenzofuran

“…Similar solvent shifts are reported for TCDF in the literature; for example, in CDC13 TCDF has resonances at ca. 7.7 and 7.9 (Gray et al, 1976), and in THF-d8, they are at 7.9 and 8.2 (Norstrom et al, 1979).…”

“…Several methods for the synthesis of polychlorodibenzofurans are discussed in an excellent review by Gara et al (1981). While many of these methods produce difficult to separate mixtures of isomers, cyclization of diazotized chlorodiphenyl ethers (Gray et al, 1976) and palladium(II) acetate catalyzed cyclization of chlorinated diphenyl ethers (Norstrom et al, 1979) can produce specific isomers of chlorinated dibenzofurans. Several monoand dichloromethoxydibenzofurans have been synthesized by photochemical cyclization of suitably substituted diphenyl ethers (Tulp and Hutzinger, 1978).…”