Phosphorus chlorides groups

Hydroxy groups in activated positions are displaced by chlorine using phosphorus chlorides as for the pyridazine (680) (71MI42900). Halogen interchange reactions are to be expected. Bromination of the chloropyrazine (681) can be effected using bromine in chloroform (75JHC451). 

In most cases, the crude imino chloride is treated directly by adding it to a solution of stannous chloride saturated with dry hydrogen chloride the aldehyde is then liberated by steam distillation. The procedure is illustrated by the synthesis of o-tolualdehyde (70%). Imino chlorides have also been prepared by treatment of ketoximes with phosphorus penta-chloride, viz., RR C NOH — RCC1=NR, in preparations of benzalde-hyde and p-chlorobenzaldehyde (70-85%). As in the Stephen reaction (method 164), groups ortho to the imino chloride group hinder the reaction. 

Carboalkoxy acyl halides are made from mono esters of dibasic acids and thionyl chloride or phosphorus pentachloride. Examples are numerous. Halides with the ester group in the beta position are unstable to prolonged heating. Alkyl halide is eliminated with the formation of an anhydride. Under certain conditions a rearrangement occurs in the preparation of ester acid chlorides. The product obtained is a mixture of the expected compound and its isomer in which the ester and acid chloride groups are interchanged, viz., ROjCCHR (CI ) CO,H — RO,C(CH,) CHR COQ. The cyclic anhydride is a likely intermediate. ... 

The application of the amidrazone method is limited. Most of the other published preparations are equally divided between electrophilic halogenation, nucleophilic displacement of halogen or nitro groups, and displacement of diazo or nitrosamino groups. The conversion of triazolinones into chlorotriazoles with phosphorus chlorides may be regarded as a nucleophilic displacement reaction of the hydroxytriazole tautomer, while the preparation of chlorotriazoles by the action of chlorine on thiones is regarded as oxidative chlorination. 

Saccharin.—When ortho-sulpho benzoic acid is treated with phosphorus pentachloride the sulphonic acid group yields the stdphon chloride group and this with ammonia yields the sulphamine group. 

Literature presents numerous data on the syntheses by ML method of oxide layers of titanium, aluminum, chromium, phosphorus, tantalum and series of other elements on silica and alumina surfaces, when appropriate chloride and vapour of water are used as initial reagents [13,35,18,42]. The synthesis thus proceeds without the change of oxidation state of elements. But the stability of Si-O-M bonds in the process of gaseous treatment of element-chloride surface structures is of significant importance. Our researches have shown [44,68], that the strength of Si-O-M bonds is influenced by the thermal stability of element-oxide chloride groups, quantity of their bonds with surfaces (factor m) and series other ones. The reason for the destruction is the hydrogen chloride which educes in the process of vapour hydrolysis [68]. 

Reducing agents such as hydroiodic acid, hydrobromic acid, hypophosphorus acid, and hydrazine can be utilized in this reaction. Sulfonyl chloride group (S02C1), the most common starting chemical moiety, can be prepared from the sulfonic acid group by reaction with phosphorus pentachloride or phosphorus trichloride and chlorine (18, 20, 21, 36, 37,... 

Thionyl chloride seldom reacts with aldehyde, ketone, or ethoxy groups, thus permitting its use with many acids where phosphorus chlorides cannot be used. Surprisingly, the OH group of salicylic acid is not attacked when the acid chloride is made by this method. 

Propanol undergoes reactions characteristic of a secondary —OH group. Oxidation is highly exothermic (43 kcal/mol) but occurs above 300° C (572°F), forming acetone. It reacts with acid chlorides, chlorine, and phosphorus chloride to produce chloroacetones (toxic). It loses water molecules over acid catalysts such as alumina or sulfuric acid, to form diisopropyl ether (flammable) and propylene (flammable, forms an explosive mixture with air). It forms isopropyl acetate (mucous membrane irritant, narcotic) with acetic acid. Treatment with nitrosyl chloride or with sodium... 

Polymer Supported Reactions. The conversion of alcohols into alkyl chlorides and of acids into acid chlorides by aryl phosphines and carbon tetrachloride proceeds more rapidly when the phosphine is polymer supported. In these reactions the main pathway appears to involve inter-reaction of two phosphorus-containing groups on the same polymer molecule. ... 

Many alkylidenephosphoranes can be transformed into new phosphonium ylides by reactions which take place in the side chain of a parent ylide, the a-C atom of the ylide group not being involved. Allylidenetriphenylphosphoranes react with a series of chloro compounds (alkyl chloioformates, acyl chlorides, 3-chloroacrylates, 2-chlorovinyl ketones, phosphorus chlorides) and other electrophilic compounds at the 7-C atom. Abstraction of a proton from the 7-position of the resulting phosphonium salts by a second mole of starting ylide (or proton migration) gives rise to the formation of -substituted derivatives of the original allylidenephosphoranes (equation 90). 

The procedure is not usually applicable to aminosulphonic acids owing to the interaction between the amino group and the phosphorus pentachloride. If, however, the chlorosulphonic acid is prepared by diazotisation and treatment with a solution of cuprous chloride in hydrochloric acid, the crystalline chlorosulphonamide and chlorosulphonanilide may be obtained in the usual way. With some compounds, the amino group may be protected by acetylation. Sulphonic acids derived from a phenol or naphthol cannot be converted into the sulphonyl chlorides by the phosphorus pentachloride method. 

Alkyl halides are such useful starting materials for preparing other functional group types that chemists have developed several different methods for converting alcohols to alkyl halides Two methods based on the inorganic reagents thionyl chloride and phosphorus tnbromide bear special mention... 

Thionyl chloride and phosphorus tribromide are specialized reagents used to bring about particular functional group transformations For this reason we won t present the mechanisms by which they convert alcohols to alkyl halides but instead will limit our selves to those mechanisms that have broad applicability and enhance our knowledge of fundamental principles In those instances you will find that a mechanistic understand mg IS of great help m organizing the reaction types of organic chemistry... 

Direct chlorination of 3,6-dichloropyridazine with phosphorus pentachloride affords 3,4,5,6-tetrachloropyridazine. The halogen is usually introduced next to the activating oxo group. Thus, 1,3-disubstituted pyridazin-6(l//)-ones give the corresponding 5-chloro derivatives, frequently accompanied by 4,5-dichloro compounds as by-products on treatment with chlorine, phosphorus pentachloride or phosphoryl chloride-phosphorus pentachloride. 

The second most important nucleophilic substitution in pyridazine A-oxides is the replacement of a nitro group. Nitro groups at the 3-, 4-, 5- and 6-position are easily substituted thermally with a chlorine or bromine atom, using acetyl chloride or hydrobromic acid respectively. Phosphorus oxychloride and benzoyl chloride are used less frequently for this purpose. Nitro groups in nitropyridazine A-oxides are easily replaced by alkoxide. The... 

Pyridazinecarboxamides are prepared from the corresponding esters or acid chlorides with ammonia or amines or by partial hydrolysis of cyanopyridazines. Pyridazinecarboxamides with a variety of substituents are easily dehydrated to nitriles with phosphorus oxychloride and are converted into the corresponding acids by acid or alkaline hydrolysis. They undergo Hofmann degradation to give the corresponding amines, while in the case of two ortho carboxamide groups pyrimidopyridazines are formed. 

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