10.10- dibromo-2,8-difluoro

Methane Dibromo-difluoro- ElOa. 37/46 (Toxicity). 630 (Educt) ElOb,. 438/441/467t, /481, 484f./ 488 fT./500/667/671 (Fduct) E10b2, 10/284 (Educt)... 

The best known of the hahdes are the trialkyldihalo- and triaryldihaloantimony compounds. The dichloro, dibromo, and diiodo compounds are generally prepared by direct halogenation of the corresponding tertiary stibiaes. The difluoro compounds are obtained by metathasis from the dichloro or dibromo compounds and silver fluoride. The diiodo compounds are the least stable and are difficult to obtain ia a pure state. The tri alkyl- and triaryldichloro- and dibromoantimony compounds are all crystalline soHds which are stable at room temperature that but decompose on heating ... 

The preparation of e/n-difluoro compounds by the oxidative fluorodesul-furization ot 1,3-dithiolanes readily proceeds by treatment with a pyridinium polyhydrogen fluoride-Af-halo compound reagent the latter serves as a bromonium ion source [2], l,3-Dibromo-5,5-dimethylhydantoin is the most effective of several At-halo oxidants. It is believed that /V-halo compounds combine with hydrogen fluoride to generate in situ halogen fluorides, the oxidants. Formation of gem-difluorides from dithiolanes derived from ketones is efficient and rapid, even at -78 °C, whereas the reaction of dithiolanes derived from aldehydes requires higher temperature (0 °C) (equation 4). 

The gem-dichloro and gem-dibromo analogues (24e and 24f) are more potent inhibitors of HLE compared to PPE, whereas the gem-difluoro (3-lactam 24a is equally efficient against the two enzymes (Table 11.4).34... 

These products obviously arose from metallation at unsubstituted ring positions in the starting tetrahalobenzene. To force metallation at the carbon-bromine bonds, they used 2,6-dibromo-3,5-difluoro-p-xylene which, with magnesium in THF gave mainly mono-adduct. With butyllithium, only the bis-adduct was obtained (15%). No mention was made of syn/anti isomers of the bis-adducts. 

When diphenylacetylene dissolved in cold chloroform reacts with iodine monofluoride suspended in trichlorofluoromethane, the iodine atoms in the primary addition product are easily replaced by fluorine to give l,1,2,2-tetrafluoro-1,2-diphenylethane (60%) along with benzil (10%). Since the C —Br bond is stronger than the C —I bond, the reaction of bromine monofluoride with diphenylacetylene gives 1,1-dibromo-2,2-difluoro-1,2-diphenylethane (65%) and benzil (15%). 

Trifluoromethyl-substituted aromatic compounds are obtained by reacting methyl arenecar-bodithioates with tetrabutylammonium dihydrogen trifluoride and l,3-dibromo-5.5-dimethyl-hydantoin. The use of /V-bromosuccinimide or A-iodosuccinimide instead of l,3-dibromo-5,5-dimethylhydantoin affords difluoro(methylsulfanyl)methyl-substitutcd aromatics.62... 

The products ArCF2SMe are assumed to be precursors of ArCF3. Indeed, l-(tri-fluoromethyl)naphthalene is obtained in 83% yield by the reaction of l-[difluoro(methylsul-fanyl)mcthyl]naphthalene with tetrabutylammonium dihydrogen trifluoride/ l,3-dibromo-5,5-dimethylhydantoin. It should be noted that under the oxidative desulfurization conditions the electron-rich aromatic compounds can undergo ring bromination. 

DBU (4.17 g, 27.4 mmol) was slowly added with stirring to a solution of 1,3-dibromo-l, l-difluoro-4-phenyl-butane (4, Ar = Ph 3.00 g, 9.15 mmol) in Et20 (15 mL) at a rate that maintained the temperature below 30 C. Solid DBU HBr salt formed during the addition. The resulting mixture was stirred for an additional 15 min. It was then diluted with EtzO (10 mL), and washed with 3 M HC1 (2 x 20 mL) to dissolve the salt. The Et,0 phase was separated and dried (CaCl2). Evaporation of the volatile material left a pale-yellow liquid yield 0.84g (55%) (E/Z) 9 1. 

Propane 1.2-Dibromo-l.l-difluoro-2-methyl- ElOb, 195 (COOH -CF.Br)... 

Propane 3-Butyloxy-l, 3-dibromo-1.1-difluoro- EI0b2. 92 (Educt)... 

Ethane 2-Chloro-1.2-dibromo-l.2-difluoro-l-phenylthio-E10b2.154 (Educt)... 

Ethane 1.1-Dibromo-2.2-difluoro-2-methylthin-l-(4-nitro-phenyl)-ElOa. 248 (2H 2Br 2SR... 

Nonane l,3-Dibromo-l.l-difluoro-ElOb, 485 (Br2CF2 + En) C9H,6FNO... 

Butane 1,3-Dibromo-l,l-difluoro-4-phenyl- EI0b2, 97 (Educt)... 

Propanoate Ethyl 2.2-Dibromo-3.3-difluoro-3-phenyl- ElOb, 375 (In + BrF)... 

Ethane 2.2-Dibromo-1,1-difluoro-l-methylthio-3-(l-naphthyl)- ElOa,... 

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