Phosphorus pentachloride isomerism

Two isomeric alcohols, known as vetivenol, also exist in the oil. By treatment with phosphorus pentachloride this mixture of alcohols is converted into a chloride, or mixture of chlorides, which on reduction yields an artificial vetivene, having the following characters —... 

The migrating group retains its configuration. Some reaction conditions can lead to syn-anti isomerization at a rate exceeding rearrangement, and when this occurs, a mixture of products is formed. The reagents that have been found least likely to cause competing isomerization are phosphorus pentachloride and p-toluenesulfonyl chloride.283... 

Beckmann rearrangement org chem An intramolecular change of a ketoxime into its isomeric amide when treated with phosphorus pentachloride. bek-man re-g ranj-mont ... 

The isomeric tricyclo[3.3.2.0 ]decane hydrocarbon (396) has also recently yielded to synthesis Thus, reaction of 394a with either thionyl chloride or phosphorus pentachloride led to rearrangement and formation of chloride 395a. Alternatively,... 

Fusco and Rossi797 observed the rupture of the pyrazole ring when 4-nitrosopyrazoles (81) were treated with phosphorus pentachloride, forming isomeric chlorocyanoazines (82 and 83). The reaction is evidently similar to the second-order Beckmann rearrangement.798... 

True 3-imino-2,3-dihydrobenz[d]isothiazole-l,1-dioxides (82) are capable of existence provided they bear an alkyl or aryl substituent in 2-position as in saccharin anils (23). The free imino compound (82a R = Me, R =H) is obtained from isomerization of o-cyano-V-methyl-phenylsulfonamide in the presence of methylamine,256 or more generally preparation of 82 may start from o-cyanophenylsulfonyl chloride together with an excess of amine.3, 256 A straightforward approach uses cyclization of an o-sulfamylbenzamide monosubstituted at each amide function, like o-(iV-phenylsulfamyl)benzanilide (83)257 with phosphorus pentoxide, phosphorus pentachloride, or preferably phosphorus oxychloride.135,257 Similarly, 2-chlorocarbonylbenzene sulfonyl chloride... 

Tetrolic acid has been prepared by treatment of acetoacetic ester with phosphorus pentachloride followed by dehydrochlorination of the reaction products by the base-catalyzed isomerization of 3-butynoic acid and by the treatment of 4,4-dibromo-3-methyl-2-pyrazolin-5-one with alkali followed by acidification. ... 

When either 1,3,4,5-tetra-O-acetyl-D-fructopyranose or penta-O-acetyl-A eto-D-fi uctose is treated with a mixture of phosphorus pentachloride and aluminum chloride in acetic anhydride, the product is 1,3,4,5-tetra-O-acetyl-/3-D-fructopyranosyl chloride ( /3-acetochloro-D-fructose ). If, however, 1,3,4,5-tetra-O-acetyl-D-fructose is treated with phosphorus pentachloride in acetic anhydride, without the addition of aluminum chloride, an isomer is formed. This second product is very much more stable than the first, and Brauns noted that, during the quantitative estimation of acetyl, only very small amounts of chlorine were split off by alkali at 0°. Brauns suggested that this compound is an isomeric tetra-O-acetyl-D-fruc-tosyl chloride, and it was considered by Hudson to be a-acetochloro-... 

This so-called Beckmann transformation has been of great significance for the explanation of the constitution of the isomeric oximes. If- eg., phosphorus pentachloride is allowed to act on both of the above formulated stereoisomeric oximes of the brombenzophenone, the same compounds are not obtained from both, but two different ones, which, as follows from their saponification products, correspond on the one hand to the benzoyl derivative of bromaniline, and, on the other, to the brombenzoyl derivative of aniline ... 

Bromocodide is produced when codeine is gently boiled with hydro-bromic acid [81-84] when codeine [18, 37] and (/(-codeine [12] are treated with phosphorus pentachloride and when codeine is. treated with thionyl bromide, excess of which causes production of 1-bromo-bromocodide [85], In the same way morphine [14] and a-isomorphine [16] can be converted to bromomorphide, which yields bromocodide on methylation [17], Attempts to isomerize these bases have failed. 

When W-acetyltetrahydrojervine (LXIV) is reacted with phosphorus pentachloride a desoxychloro derivative (LXXXIV) is formed which on ring scission with sulfuric acid in acetic anhydride-acetic acid gives rise to the 0,iV-diacetyl compound LXXXV. This on partial hydrolysis with alkali affords an W-acetyl compound (LXXXVI) which on reacetylation yields an isomeric diacetyl derivative (LXXXVII) in analogy with similar reactions of tetrahydrojervine. The AT-acetyl derivative (LXXXVI) on chromic acid oxidation formed a ketone (LXXXVIII) with a reactive carbonyl (66). 

The same phosphazo-phosphonyl compound MeONP2Cl4 results from the reaction of either phosphorus pentachloride and ethyl P-methyl phosphon-amidate or methyltetrachlorophosphorane and diethyl phosphoramidate (EtO)2P(0)NH2, and although the structure could not be determined by chemical means, formula (80) rather than the isomeric (81) is suggested by C1 n.q.r. measurements. ... 

In the reaction of N-disubstituted carboxylic acid amides with phosphorus pentachloride the corresponding iminium chlorides are formed, and again partially isomerization occurs in amides with a-hydrogens. For example, the iminium chloride XXIII and the vinylamine XXIV are formed in the reaction of disubstituted acetic acid diethylamides with phosphorus pentachloride ( 7,262 ... 

Crotonic acid was discovered in croton seeds by Pelletier and Caventou by saponifying the oil, adding tartaric acid, and distilling, but was more definitely characterised by T. Schlippe. Crotonitrile C4H5N, present in crude mustard oil, yields on hydrolysis with alcoholic potash crotonic acid C4He02, and crotonitrile is formed from allyl iodide and potassium cyanide hence the acid was formulated CH2 = CH-CH2 C02H. An isomeric acid was discovered by A. Geuther in the form of an acid chloride in the products of the action of phosphorus pentachloride on acetoacetic ester. 

The isomerization of N-phenyl aUylimidates (e.g., 20) also provides access to aUyhc ketene N,0-acetals (Scheme 7.11) [23, 24]. Imidates of type 20 can be synthesized from phenyl amides by treatment with phosphorus pentachloride to yield the corresponding imidochloride followed by addition of the appropriate lithium aUyl aUc-oxide. The thermal isomerization of 20 to the ketene N,0-acetal requires high temperamre conditions (e.g., refluxing decalin). 

Reaction of j8-maltotriose hendeca-acetate with phosphorus pentachloride afforded 2, 2",3,3, 3",4",6,6, 6"-nona-0-acetyl-2-(9-trichloroacetyl- -maltotriosyl chloride (42%), which could be isomerized (TiCh in chloroform) to the corresponding a-chloride. 2 Selective ammonolysis of the trichloroacetyl group in the a- and jS-chlorides gave the 2-hydroxy derivatives. 

Ammonolysis of the diacid chloride, obtained from the treatment of C,C -neocarboranecarboxylic acid with phosphorus pentachloride, gives the diacid amide. Pyrolysis of the latter compound does not result in the formation of a cyclic imide, as is observed in the corresponding 1,2-C2B 1 qH 12 derivative (Section III, C, 6) (335). A number of silyl derivatives have been prepared from dilithioneocarborane, and again, in contrast to the isomeric silylcarboranes (Section III, C, 8), they do not tend to form exocyclic derivatives (353). These observations are consistent with the 1,7-arrangement of the carbons in the neocarborane icosahedron. 

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