Difluorobenzoate

Interestingly, the photolysis of methyl 3-azido-2.6-difluorobenzoate (61) in diethylamine yields, in addition to the two expected 3//-azepines 62 and 63, a third azepine 64 formed by nucleophilic displacement of allylic fluorine from the 3-position by diethylamine.188 Displacement of allylic halogen from haloazepines has been noted previously.177... 

S)-2-chloro-3-methylbutanoyloxy] biphenyl-4-yl 4-undecyloxy-2,3-difluorobenzoate [164] 111 H23C11O- -OOCC hC1CH(CH3)2 C-Sc -N -1 40 P2i 4... 

Fig. 29. Crystal structure of 4-[(2S)-chloro-3-methylbutanoyloxy]biphenyl-4 yl 4-undecy-loxy-2,3-difluorobenzoate along tbe x-axis (Reprinted from [164])... 

The metabolism of 2,5- and 3,5-difluorobenzoate by Pseudomonas putida strain JT103 has been examined by F NMR (Cass et al. 1987). 1 2 Dioxygenation took place with both substrates (Figure 9.34a,b), and for the 2,5-difluorobenzoate this dominated the alternative distal 1 6 dioxygenation... 

Diflubenzuron breakdown by hydrolysis, soil degradation, or plant and animal metabolism initially yields 2,6-difluorobenzoic acid and 4-chlorophenylurea. Ultimately, the end products are... 

Figure 17.1 Generalized degradation pattern for diflubenzuron. Diflubenzuron (A) degrades initially to 2,6-difluorobenzoic acid (B) and 4-chlorophenylurea (C). 2,6-Difluorobenzoic acid (B) degrades to 2,6-difluorobenzamide (D) and 4-chlorophenylurea (C) degrades to 4-chloroaniline (E).

Intestinal absorption of diflubenzuron in laboratory rats, measured as the sum of urinary and biliary excretion, decreases with increasing dose from 50% at a single oral dose of 4 mg/kg BW to 4% at 900 mg/kg BW. Excretion is almost complete after 75 h at that time, up to 4% of the administered dose is recovered from skinned carcasses (Willems etal. 1980). About 80% of diflubenzuron metabolites excreted by rats seem to have the basic diflubenzuron structure intact. Three metabolites are largely excreted as conjugates in the bile. One metabolite, 2,6-difluorobenzoic acid, is excreted largely in urine. Its counterpart, 4-chlorophenylurea, was not present in urine or bile in appreciable quantity, nor was 4-chloroaniline detected (Willems et al. 1980). Lifetime feeding studies of 4-chloroaniline, a relatively common diflubenzuron metabolite, showed no compound-related effects in laboratory mice and rats (Gartrell 1981). 

In the solid state, the most common structure of the monocarboxylates, in the absence of any major steric demands, is that of a linear polymer 33, but tributyltin 2,6-difluorobenzoate forms a cyclic tetramer, (Bu3SnOCOAr)4.349... 

The soil was aged aerobically for two weeks, then submerged under water for two weeks. Finally, additional water and catfish were added with monitoring of residues for twenty-eight days. For soil treated at 0.55 ppm, 64% of the initial dose was released from the soil, but only 2.3% of the applied radiolabel was found in the water upon termination of the study. Water residues consisted mostly (>93%) of 4-chlorophenylurea, accompanied by difluorobenzoic acid (3-5%), 4-chloroaniline (0-1%), and diflubenzuron (0.4-1.5%). An average of 66% of the soil residues were extractable with methanol, consisting predominantly of unmetabolized diflubenzuron (74-84%) and 4-chloroaniline (11-17%). For soil treated at 0.55 ppm, fish residues quickly reached a plateau after three days at about 4 and 10 ppb for muscle and viscera, respectively. Hence, Booth and Ferrell (14) concluded that bioaccumulation of diflubenzuron residues from marsh applications should be minimal. 

The acidity and dielectric constant of the reaction media can have a profound effect on the fluorination process. Studies concerning the fluorination of a model substrate, 4-fluorobenzoic acid, in a variety of solvents showed that conversion of the substrate to 3,4-difluorobenzoic acid (Table 5) rose as the acidity of the solvent increased, due to the increased interaction between fluorine and the reaction medium (Fig. 56) [147]. 

---