Carbon tetrachloride reagent

Two routes for the reaction of substrate with the triphenylphosphine-carbon tetrachloride reagent are now recognized.61 62>64 Direct interaction (76) of the substrate with the initially formed dipolar associate leads to the formation of chloroform and the intermediate phosphonium salt (77). 

Allylie chlorides. Allylic alcohols can be converted into allylic chlorides with no, or slight, rearrangement by the triphenylphosphine-carbon tetrachloride reagent/... 

Nucleophilic Attack at Halogen. Further studies have been reported of the reactions of diols with the triphenylphosphine-carbon tetrachloride reagent. It has now been applied to 1,2-diols (in the presence of potassium carbonate) to form epoxides and to the trans-6 o (84), the nature of the product depending on the relative amounts of phosphine and diol present. The major product of reactions involving equimolar quantities of phosphine and diol is (85). The cyclodehydration product (86) is formed in only poor yield. In the presence of carboxylic acids, the triphenylphosphine-carbon tetrachloride system causes ring-opening of epoxides with the formation of c -enol esters, the reaction presumably proceeding via nucleophilic attack by the oxirane at an acyloxyphos-phonium intermediate. ... 

Carbon tetrachloride, reagent purity, tested with dithizone for absence of silver... 

In a related olefination, carboxylic esters and 6- or 7-membered lactones react with an excess of the triphenylphosphine-carbon tetrachloride reagent to give variable yields of 2,2-dichlorovinyl ethers, e.g. (54) - (55)/"... 

The transformation of aldonolactones into the corresponding dichloromethylene derivatives on reaction with triphenylphosphine-carbon tetrachloride reagent has been described (Scheme 10). This reagent is of more general applicability than the bis(dimethylamino)phosphine-carbon tetrachloride reported earlier (Vol. 18, p.34). Ester carbonyl groups are also dichloromethylated. 

Use of the triphenylphosphine-carbon tetrachloride reagent, with or without the addition of triethylamine, provides an efficient peptide coupling procedure, both methods involving the intermediate phosphonium ester salt (94) the presence of triethylamine obviates the use of two equivalents of reacting amine. 

A related technique involves a tris(dimethylamino)phosphine-carbon tetrachloride reagent, where interaction with carboxylic acids gives anhydrides and tris(dimethylamino)phosphonium chloride (95), which can, in turn, activate remainingacid for furtherreaction, e.g. tocomplete anhydride formation, giving the overall process shown in Scheme 31. Alternatively, it can be used to effect amide-bond formation, when nucleophilic attack by amine on... 

Nitration using this reagent was first investigated, by Francis. He showed that benzene and some of its homologues bromobenzene, benzonitrile, benzoyl chloride, benzaldehyde and some related compounds, and phenol were mono-nitrated in solutions of benzoyl nitrate in carbon tetrachloride anilines would not react cleanly and a series of naphthols yielded dinitro compounds. Further work on the orientation of substitution associated this reagent with higher proportions of o-substitution than that brought about by nitric acid this point is discussed below ( 5.3.4). 

Because of the chemical similarity between benzoyl nitrate and the acetyl nitrate which is formed in solutions of nitric acid in acetic anhydride, it is tempting to draw analogies between the mechanisms of nitration in such solutions and in solutions of benzoyl nitrate in carbon tetrachloride. Similarities do exist, such as the production by these reagents of higher proportions of o-substituted products from some substrates than are produced by nitronium ions, as already mentioned and further discussed below. Further, in solutions in carbon tetrachloride of acetyl nitrate or benzoyl nitrate, the addition of acetic anhydride and benzoic anhydride respectively reduces the rate of reaction, implying that dinitrogen pentoxide may also be involved in nitration in acetic anhydride. However, for solutions in which acetic anhydride is also the solvent, the analogy should be drawn with caution, for in many ways the conditions are not comparable. Thus, carbon tetrachloride is a non-polar solvent, in which, as has been shown above,... 

Allylic brommations are normally carried out using one of a number of special ized reagents developed for that purpose N Bromosuccimmide (NBS) is the most fre quently used of these reagents An alkene is dissolved m carbon tetrachloride N bromo succimmide is added and the reaction mixture is heated illuminated with a sunlamp or both The products are an allylic halide and succimmide... 

Other procedures have also been reported (38,110,111). The properties and chemistry of 9-BBN have been reviewed (112). The reagent is a white crystalline soHd, stable indefinitely at room temperature, soluble in hexane, carbon tetrachloride, benzene, tetrahydrofuran, and diethyl ether. It exists as a... 

Acid Chloride Formation. Monoacid chlorides of maleic and fumaric acid are not known. Treatment of maleic anhydride or maleic acid with various reagents such as phosgene [75-44-5] (qv), phthaloyl chloride [88-95-9] phosphoms pentachloride [10026-13-8] or thionyl chloride [7719-09-7] gives 5,5-dichloro-2(5JT)furanone [133565-92-1] (4) (26). Similar conditions convert fumaric acid to fumaryl chloride [627-63-4] (5) (26,27). NoncycHc maleyl chloride [22542-53-6] (6) forms in 11% yield at 220°C in the reaction of one mole of maleic anhydride with six moles of carbon tetrachloride [56-23-5] over an activated carbon [7440-44-4] catalyst (28). 

Many reagents are able to chlorinate aromatic pyrazole derivatives chlorine-water, chlorine in carbon tetrachloride, hypochlorous acid, chlorine in acetic acid (one of the best experimental procedures), hydrochloric acid and hydrogen peroxide in acetic acid, sulfuryl chloride (another useful procedure), etc. iV-Unsubstituted pyrazoles are often used as silver salts. When methyl groups are present they are sometimes chlorinated yielding CCI3 groups. Formation of dimers and trimers (308 R = C1) has also been observed. 

Dipping solution Mix 2 ml antimony(V) chloride with 8 ml carbon tetrachloride. Storage The reagent solution should always be freshly prepared. 

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