Haloalkyl group

Haloall lation. Haloalkyl groups can be introduced directiy by processes similar to Friedel-Crafts alkylation into aromatic and, to some extent, ahphatic compounds. Because halo alkylations involve bi- or polyfunctional alkylating agents, they must be performed under conditions that promote the initial halo alkylation but not, to any substantial degree, subsequent further alkylations with the initially formed haloalkylated products. 

Hydroxyalkyl groups attached to pyridopyridazines have been converted to haloalkyl groups by standard methods and the products reacted with amines. Ketones have been converted to hydrazones and oximes and the resulting derivatives deprotected during syntheses. 

As well as 3-haloalkylamines, substances with haloalkyl groups attached to carbons bonded to oxygen can be used. An interesting example is bromoacetylcholine, which acts as a tethered agonist acting on nicotinic receptors. 

Another reaction of dehalogenation, the oxidative dehalogenation of haloalkyl groups, summarized in Fig. 11.3,b (Chapt. 8 in [50]), has also been observed in mammals and other organisms. Here, the haloalkane is oxidized by a cytochrome P450 enzyme to form a hydroxylated intermediate that loses HX to become a carbonyl derivative. The latter is then reduced by dehydrogenases to the corresponding alcohol (Fig. 11.3,c), or, when the carbonyl derivative is an aldehyde, oxidation to the acid can occur (Fig. 11.3,c). 

This section focuses on the nonprotein amino acids containing alkyl or haloalkyl groups as side chains. There are number of examples containing linear and branched alkyl chains, such as ethyl, propyl, and t-butyl. Some amino acids contain the cyclopropyl group as side chains (coronamic acid derivatives and BZR-cotoxin 11). Furthermore, dysamides, a class of diketopiperazines, contain nonprotein amino acids with chlorinated alkyl side chains. ... 

To introduce phosphorus as the charge-canying moiety, dyes that contain haloalkyl groups are treated with phosphines such as dimethylphenylphosphine (e.g., 56) [151]. 

Very recently, the combination of a reactive group at C-4 (an aldehyde or an imine) and a tu-haloalkyl group at nitrogen in different azetidin-2-ones enabled the synthesis of pharmaceuticaly relevant piperazine, morpholine, and 1,4-diazepane annulated /3-lactams upon reductive ring closure <2006JOC7083>. 

Reaction 92 with H02 results in formation of a hydroperoxide. Since the nature of the haloalkyl group is not likely to affect greatly the reactivity for this process, rate constants similar to that of 5 x lCT12cm3 molecule-1 s-1 for methylperoxy are expected. In view of the low concentrations of H02 radicals in the troposphere, this reaction is expected to be of only minor significance, except under conditions where the NO and N02 concentrations are also low. 

In Fig. 3 one finds a variety of functional groups that may be subdivided as follows haloalkyl groups [14-16], saturated esters (acetate [17], and benzoate [18,19]) unsaturated esters (methacrylate [19,20], acrylate [21], cinnamate [20], and others [21]) malonate and related esters [22-24] ethers and oligo(oxyethylenes) [25-28] imides [29,30] alkylsilyloxy groups [31] perfluoroalkyls [32-34] and protected carbohydrate groups [35]. Vinyl ethers with mesogenic (liquid-crystal forming) substituents will be treated separately in Section II. B.2. 

Since fluoroalkyl groups are uniformly acid-strengthening and the order of magnitude of the effect, relative to other haloalkyl groups, is consistent with electronegativities F > Cl, etc., it may be expected that the same situation occurs when fluorine is attached to unsaturated carbon. Inspection of the data in Table 4.5 quickly indicates a more complicated situation because, while fluorine substitution increases the acidity relative to the hydrocarbon analogue, the acidities are lower than the corresponding chlorocarbon compounds in the cases of the acrylic acids and phenols. 

Cyclopropene 12, bearing a 1-haloalkyl group, undergoes a stereospecific allylic rearrangement on heating the halogen attacks from the face opposite to the ethoxycarbonyl substituent at... 

H. Eckert, I. Lagerlund and I. Ugi, Fragmentation with Supernucleophiles - VI. 6-Haloalkyl Groups as Functional Protection in Peptide Synthesis. A Kinetic Study of the Reaction of the Cobalt(I)phthalocyanine Anion with Organic Halides, Tetrahedron 32 (1977) 2243-2247. 

Currently, anionic polymerization is regarded as one of the best methods available to prepare end-functionalized polymers. Vinyl polymers with haloalkyl groups at one chain end were prepared by anionic polymerization, followed by termination of the living anion with an excess of 1,2-dichloroethane or 1,4-dibromobutane [102]. These polymers served as macroinitiators for the polymerization of 2-methyl-2-oxazoline (MeOZO) and aromatic vinyl monomers (Scheme 11.27). 

Haloalkyl methacrylate Single T , FTIR II had a haloalkyl group of chloromethyl, 2-chloroetiiyl, 3-chloropropyl, 2-bromoethyl, or 2-iodoethyl Low et al. (1994a), Opazo et al. (1994)... 

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