Synthesis bromoalkane

A viable iron carbonyl-mediated reduction process converts acid chlorides and bromoalkanes into aldehydes [3, 6]. Yields are high, with the exception of nitro-benzoyl chloride, and the procedure is generally applicable for the synthesis of alkyl, aryl and a,(i-unsaturated aldehydes from the acid chlorides. The reduction proceeds via the initial formation of the acyl iron complex, followed by hydride transfer and extrusion of the aldehyde (cf. Chapter 8). 

Priihs et al. found an elegant application for a seemingly remote hydroxy group in the sidechain [43]. The remoteness of the hydroxy group implies a mode of introduction to the central imidazole ring different to the epoxide method developed by Arnold (hydroxyethyl) and Thiel (hydroxyhexyl). Indeed, Priihs et al. modilied the classic method of imidazo-lium salt synthesis by using a bromoalkane as carrier for the hydroxy functional group. In this way, they reacted A-mesityl imidazole with l-bromo-ta-hydroxyalkanes to obtain the... 

The technique for the introduction of lipidic groups into compounds that is favored by the authors is the use of lipoamino acids (Laas) (Fig, 1). These are a-amino acids with alkyl sidechains that can be varied in length, substitution, and degree of unsaturation simply by altering the bromoalkane used in the synthesis (6). The benefits of Laas include the ability to couple them using standard peptide coupling procedures, making them ideal for use in solid phase syntheses. Their bifunctional nature means they can be introduced into a peptide at any point in the sequence and the number of Laas introduced is easily varied. 

The development of regiospecific trapping of radicals arising by cyclization should prove useful in synthesis. Irradiation of the bromoalkane (196) in the... 

Fig. 47 Dimerization in the synthesis of polychloroalkanes (a) reductive dimerization of terminal trichlorides followed by hydrogenation [72, 73] (b) electrolytic dimerization of m-chlorocar-boxylic acids with loss of CO2[50] (c) electrolytic dimerization of a.oj-dichloroalkanes [50, 74] (d) reductive coupling of a,a-dichloro-

The reaction of triphenylphosphine with carbon tetrabromide in acetonitrile has been studied by conductimetric titration and found to be rapid, leading to the formation of the salt (87), which was isolated from the reaction mixture. Treatment of alcohols with the triphenylphosphine-carbon tetrabromide reagent in the presence of radiolabelled bromide ion gives a rapid, low-temperature procedure for the synthesis of radiolabelled bromoalkanes under neutral conditions. ... 

The trichloromethy1-3-bromoalkanes (38) also add to carbonyl groups in a formal [3+2]-type cycloaddition reaction under electrolytic conditions where the intermediate is thought to be the dichloromethyl anion (39)." Trost has extended the scope of his [3+2] eyeloaddltlon reaction to include the synthesis of tetra-hydrofurans. He found that the stannyl acetate (40) rather than the corresponding silyl acetate gives high yields of the... 

The Kobayashi group reported a one-pot synthesis of l,4-oxathiino[2,3-l)]quinoxalines 152a or -pyrazines 152b by treating 2,3-dichloroquinoxa-line or -pyrazine with sodium sulfide nonahydrate in either DMF or DMSO at room temperature, and the resulting 2-chloro-3-sodiosulfanyl-quinoxaline or -pyrazine intermediate with 1-aryl-2-bromoalkan-1-ones, followed by sodium hydride in DMF or DMSO at room temperature (Scheme 73) (13HCA1452). 

An alternative method for the synthesis of bromoalkanes from primary and secondary alcohols is through the use of phosphorous tribromide, PBrj. 

Almost all LC-polyethers mentioned in this section were prepared via the Williamson ether synthesis from a mesogenic diphenol and (di)bromoalkanes. For instance a linear LC-polyether was obtained from the cesium salt of a diazine-diphenol and 1,10-dibromodecane in NMP (210) [323]. In two cases, (211) [324] and (209) [325] interfacial polycondensation were performed using sodium hydroxide in combination with a phase-transfer catalyst and an organic solvent. Almost all LC-polyethers prepared in this... 

Another research group published numerous studies of syntheses and physical properties of LC-polyethers having linear chains, hyperbranched and cyclic structures or containing discotic mesogens [327-341]. All these different LC-polyethers were prepared via the normal Williamson ether synthesis involving the nucleophilic attack of a phenoxide ion onto a bromoalkane. For instance, numerous linear LC-polyesters were prepared from the mesogenic diphenols outlined in (214) and formulas (215a,b) [327,337]. 

Bromoboration Reactions. BBrj does not add to isolated double bonds, but reacts with allene spontaneously even at low temperature to give (2-bromoallyl)dibromoborane, which provides stable (2-bromoallyl)diphenoxyborane by the addition of anisole. The diphenoxyborane derivative reacts with carbonyl compounds to give 2-bromohomoallylic alcohols in high yields (eq 12). Bromoboration of 1-alkynes provides (Z)-(2-bromo-l-alkenyl)dibromoboranes stereo- and re-gioselectively (eq 13), which are applied for the synthesis of trisubstituted alkenes, a,p-unsaturated esters, and 7,8-unsaturated ketones, bromodienes, 1,2-dihalo-l-alkenes, 2-bromoalkanals, and (3-bromo-oi,3-unsaturated amides. ... 

Pure AE homologs can be prepared by reacting the corresponding 1-bromoalkane with, e.g., triethylene glycol, hexaethylene glycol, or nonaethylene glycol (13). This approach is especially suitable for synthesis of " C-labeled materials. AE carboxylates are prepared by oxidation of AE with chromic/sulfuric acid, followed by extraction of the acids from saturated salt solution into methylene chloride (135). 

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