Halogens reaction with carbon

The iron slurries show exceptional reactivity toward oxidative addition reactions with carbon halogen bonds. In fact, the reaction with C.FcI is so exothermic that the slurry has to be cooled to 0 °C before the addition of C F L The reaction of iron with C F Br is also quite exothermic, hence, even for this addition, the iron slurry is cooled to about 0 ° C. The organoiron compound formed in the above reactions, solvated Fe(C.F )2, reacts with CO at room temperature and ambient pressure to yiela Fe(C,F3)2(CO)2(DMEL. 

Plutonium reacts with hydrogen at high temperatures forming hydrides. With nitrogen, it forms nitrides, and with halogens, various plutonium hahdes form. Halide products also are obtained with halogen acids. Reactions with carbon monoxide yields plutonium carbides, whde with carbon dioxide, the products are both carbides and oxides. Such reactions occur only at high temperatures. 

It has been demonstrated in CHEC-II <1996GHEC-II(7)431> that halogen substituents as well as other good leaving substituents can be readily replaced by carbon nucleophiles, for example, cyanide ion or active methylene compounds. Also, direct cyanation of l-phenylpyrazolo[3,4-i/]pyrimidine was demonstrated. Since then, reactivity toward carbon nucleophiles has not received much attention. However, a few interesting reactions with carbon electrophiles have been reported in the last few years. Thus, reacting 154 with 155 affords 156 (Equation 9) <2002BML1687>. 

Considerable interest has developed in the method of conversion of alcohols, by their reaction with carbon tetrachloride and tertiary phosphines (usually triphenylphosphine), into the corresponding alkyl chlorides.65 The reaction is considered to proceed by an ionic mechanism involving nucleophilic displacement on halogen, as shown. 

Lithio-heterocycles have proved to be the most useful organometallic derivatives they react with the whole range of electrophiles in a manner exactly comparable to that of aryllithiums and can often be prepared by direct metallation (C-hydrogen deprotonation), as well as by halogen exchange between a halo-heterocycle and an alkyllithium. As well as reaction with carbon electrophiles, Uthiated species are often the most convenient source of heterocyclic derivatives of less electropositive metals, such as zinc, boron, silicon and tin, as will be seen in the following sections. 

The a-halogenation of tertiary phosphine oxides has been investigated. Direct bromination of dibenzylphenylphosphine oxide gave all three possible diastereo-meric a,a -dibromo-derivatives (47). Alternative halogenation, via formation of the mono- or di-lithiated species followed by reaction with carbon tetrachloride, gave monochlorination products (48) with kinetically controlled diastereomeric ratios. 

Similarly, the conversion of the Si-H unit in poly(phenylsilane) into the more reactive Si-Cl and Si-Br functional group can be easily effected by the reaction with carbon tetrachloride and carbon tetrabromide, respectively (Fig. 7.19) [63]. The chlorination or bromination does not affect the Si-Ph substituent but only involves the Si-H bonds. In these reactions about 80% of the Si-H bonds can be converted into the corresponding Si-X bonds. These halogenated polysilanes are reactive polymers that can react with other types of nucleophiles such as alcohols to afford polysilanes containing alkoxy groups [63]. 

One of the most common uses of [ C]acetyl chloride is its Lewis acid- (AICI3, SnCLi) catalyzed Friedel-Crafts reaction with aromatic or heteroaromatic substrates to produce labeled aryl/heteroaryl methyl ketones. As these intermediates are subject to several types of transformations, they have been used as key intermediates for the synthesis of a wide variety of a,)8-functionalized aryl/heteroaryl alkyl target compounds. For example, aryl/ heteroaryl methyl ketones can be (a) halogenated in the methyl group to provide substrates for reaction with carbon or nitrogen nucleophiles, (b) deprotonated so as to react with appropriate electrophilic partners, (c) subjected to stereoselective carbonyl group reduction to alcohols, or (d) reduced to aryl/heteroaryl alkyls. Such transformations can be conducted sequentially in many combinations. 

---