Aryl groups fluorinated

Table 3 summarizes the scope and limitation of substrates for this hydrogenation. Complex 5 acts as a highly effective catalyst for functionalized olefins with unprotected amines (the order of activity tertiary > secondary primary), ethers, esters, fluorinated aryl groups, and others [27, 30]. However, in contrast to the reduction of a,p-unsaturated esters decomposition of 5 was observed when a,p-unsaturated ketones (e.g., trans-chalcone, trans-4-hexen-3-one, tra s-4-phenyl-3-buten-2-one, 2-cyclohexanone, carvone) were used (Fig. 3) [30],... 

Organocadmium species are useful reagents for the transfer of fluorinated alkyl or aryl groups to other main group or transition metal centers. Most of the recent cases illustrating this property involve the use of Cd(CF3)2 and Cd(C6F5)2... 

Example 52 replacement of the fluorine ligand by the alkyl (aryl) group by the action of organometallic reagent has been studied by Michalski and associates. Preliminary successful results have been achieved with Grignard reagents [30]. 

In a preparatively useful process diarylamines can be cyclized photolyti-cally. Substrates having alkyl groups,fluorine, methoxyl, ethylamino, and N-alkyF - " and N-aryl groups have been used. Not all triarylamines could be cyclized, especially... 

Related bis(/3-enamino ketonato) titanium complexes with non-fluorinated A -aryl groups, FlO-23, also afforded polyethylenes with relatively low PDI of 1.2-1.4 at 25 °C (1.3 kgmmol-Ti h atm ), where the molecular weight increases with polymerization time. " ... 

Halofluorinations take place, as a rule, regioselectively (Markovnikov addition), the olefinic carbons can be substituted with a variety of substituents ranging from alkyl or aryl groups to different electron-withdrawing functions see for example refs 31 and 178-180. Bromo-fluorination of 4-/m-butyl-l-methylcyclohexene with /V-bromosuccinimide in 70% hydrogen fluoride/pyridine gave two stereoisomers 1 and 2.181... 

Chlorination is carried out in a manner similar to bromination and provides a ready route to chlorobenzene and related aryl chlorides. Fluorination and iodination of benzene and other arenes are rarely performed. Fluorine is so reactive that its reaction with benzene is difficult to control. Iodination is very slow and has an unfavorable equilibrium constant. Syntheses of aryl fluorides and aryl iodides are normally carried out by way of functional group transformations of arylamines these reactions will be described in Chapter 22. 

When the SF4C1 group is attached to the 2-position of pyridine, its fluorines are significantly shielded (+124.2 ppm) compared to the respective aryl-SF4Cl fluorines (Scheme 7.23). 

Incorporation of bulkier, more highly fluorinated aryl groups increases the Childs Lewis acidity, but calorimetric measurements on the reactions of III and V with simple Lewis bases or metallocenes reveal that back-strain upon pyramidalization at boron limits the eflFective Lewis acidity of these compounds. This notion is supported computationally.98 As an alternative to bulky, exhaustively fluorinated aryl groups, incorporation of the boron atom into an anti-aromatic 9-borafluorene ring, VI, results in comparable LA strength (Childs acidity = 0.70 0.02) to B(C6F5)3, despite the loss of two fluorine atoms. 

Carbon. The earliest compound, Xe(CF3)2 was made by action of CF3 radicals on XeF2 but it was stable for only ca. 30 minutes at room temperature. Stable species, mostly cationic in nature, can be made. Thus the reaction of fluorinated aryls, e.g., B(QF5)3, with XeF2 in the presence of BF3(OMe2), gives [ArXe]+[BF4] . The stability of such compounds depends on the nature of the aryl group and decomposition temperatures range from about -14°C for 4-FQH, to 130°C for 2,6-F2C6H3.24... 

Decarboxylative fluorination, presumably via intermediate acyl hypofluorites, has been achieved in low yield by passing a dilute stream of fluorine in nitrogen into aqueous solutions of sodium carboxy-lates. A somewhat more promising method, tolerant of aryl groups, ketones and ethers, involves reaction of a dichloromethane solution of the acid with xenon difluoride and hydrogen fluoride (equation 23). 7... 

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