With phosphoryl chloride

Monsanto has disclosed the use of carbon dioxide—amine complexes which are dehydrated, at low temperatures, with phosphoryl chloride [10025-87-3] or thionyl chloride [7719-09-7] as a viable route to a variety of aUphatic isocyanates. The process rehes on the facile formation of the intermediate salt (30).REPLACEVariations of this process, in which phosgene is used as a dehydrating agent, have been reported earlier (84). Table 2 Hsts commercially available aUphatic isocyanates. 

Several modified forms of this synthesis are available. For example, treatment of either isocyanate (28) or urethane (29) derivatives with phosphoryl chloride followed by stannic chloride has been reported to give the substituted isoquinoline [80388-01-8] (158). 

The cyclization of 5-(2-carboxyanilino)pyrimidine (170) with sulfuric acid/phosphoric acid leads to the 7-chloropyrimido[5,4-A]quinolinetriones (171) (57JCS4997, 74KGS131), the 2,4,10-trichloro compounds being obtained with phosphoryl chloride (72JHC91), whilst a formally similar cyclization of 4(6)-arylamino-5-ethoxycarbonylpyrimidines gives... 

Thiophene-2-sulfonic acid is a strong acid, similar to benzenesulfonic acid. It forms a sulfonyl chloride with phosphoryl chloride which on reduction with zinc yields thiophene-2-sulfinic acid. 

An alternative method involves reaction of an a-acylaminoketone (12) with a primary amine and subsequent ring closure of the resultant Schiff s base (13) with phosphoryl chloride. This enables the introduction of a 1-substituent as in (14) to be carried out efficiently, and if the amine were replaced with a monosubstituted hydrazine, the imidazole derivative (IS) resulted (78LA1916). 

In an effort to prepare 1 2-dihydropapaverine, Buck dehydrated catalytic reduction, followed by the action of phosphorus pentachloride in the cold. The final product was assumed to be 1 2-dihydropapaverine but Young and Robinson interpret this synthesis differently, and their formulae (V) and (VI) are given above, the final product being 3 4-dihydropapaverine (VII), which Buck thus prepared for the first time in a crystalline condition, m.p. 97-8° picrate, m.p. 151° perchlorate, m.p. 238° dec.). 

In 1949, Comforth showed that preparation of 2,5-disubstituted oxazoles was not limited to diaryloxazoles through condensation of aldehydes (benzaldehyde, n-hept-aldehyde) with a-hydroxy-amides (lactamide). The intermediate oxazolidone 13 were converted into oxazoles 14 on warming with phosphoryl chloride. ... 

Chlorodehydroxylation with phosphoryl chloride and thionation with phosphorus pentasulfide have been... 

QuinoxaIin-2-oncs are readily converted into the corresponding 2-chloroquinoxalines by treatment with phosphoryl chloride in the case of the highly insoluble 2,3-diones chlorination is effected conveniently with a mixture of phosphoryl chloride and dimethyl-aniline. The use of phosphorus pcntachloride may lead to side reactions, for example, quinoxalin-2-one (70) is converted into 2,3-... 

The first dibenz[/>,e]azepine 23 was prepared by cyclization of amidine 22 with phosphoryl chloride in refluxing nitrobenzene.103... 

Chloro-l//-l-benzazepines 2 are obtained as unstable red oils in excellent yields by heating 1 //-l-benzazepin-2(3//)-ones 1 with phosphoryl chloride in pyridine.208 Reaction conditions are important since in the absence of pyridine, or in dichloromethane solution, only poor yields of dimers, e.g. 3, are produced. The chlorobcnzazepines are stable for only short periods (24 hours in anhydrous pyridine) and rapidly polymerize. Isolation of the pure chloro compounds is difficult since they undergo very rapid hydrolysis to the benzazepinones. 

Methoxy-5//-pyrido[2,3-c]azepin-9(8//)-one (4) on chlorodehydroxylation with phosphoryl chloride in A,A, -dimethylaniline yields a mixture (20 %) of the chlorc)-6-methoxypyrido[2,3-c -azepines5and6.192 An unseparablemixture (3 7) of 5H- and 7ff-pyrido[2,3-c]azcpine-9-thione 7 and 8 is obtained on treating the pyridoazepinone 4 with phosphorus pentasulfide in warm pyridine. 

The pyrimidobenzazepinones 15 (see Section 3.2.1.5.6.) on treatment with phosphoryl chloride yield the 1-chloro derivatives 16 which are precursors for the preparation of 1-substituted pyrimido[5,4-c/]bcnzazepines, e.g. 17.7S... 

Heating phenacyl 2-aminobenzoate with phosphoryl chloride yields 2-phenyl-4,1-benz-oxazepin-5(17/)-one (1. R = H). The method has been applied to the synthesis of a number of analogs.423... 

The reaction of 5-methyl-lFf-1,4-benzodiazepin-2(3 W)-one with phosphoryl chloride gives 2-(chloromethyl)-4-methylquinazoline (18).246... 

Nucleophilic processes that generate chloroindoles are largely confined to the displacements of oxy functions and Sandmeyer reactions of diazo-nium salts [81 H( 15)547]. A low yield of 2-chloroindole was obtained by a reaction sequence that involved treatment of oxindole with phosphoryl chloride, and then treatment of the Vilsmeier salt with sodium bicarbonate [66JOC2627 86H(24)2879]. It is, however, much better to prepare this compound from 2-lithioindole (92JOC2495). With phosphoryl chloride and dimethylformamide ethyl l-hydroxyindole-2-carboxylate failed to give the expected 3-formyl derivative. Instead there was a 50% yield of the 3-chloro derivative (84CPB3678). Diazonium salts have been used as precursors in... 

In the Meisenheimer reaction of quinoline 1-oxides chlorine atoms usually enter the 2-and 4-positions, but not exclusively. 2,4-Dibromoquinoline 1-oxide was 6-chlorinated (57MI1), and the 5- and 6-nitroquinoline 1-oxides were 3-chlorinated to some extent (44JOC302). This reaction with phosphoryl chloride-phosphorus pentachloride has also been used in the preparation of chlorinated phenanthrolines (88YZ1148). 

Sometimes lateral chlorination can occur on a methyl or alkylthio substituent, especially when phosphorus pentachloride or its mixtures with phosphoryl chloride are used (91JHC1549). Reactions of 2-methyl-4(I//)-quinoline (67) exemplify this behavior (81CPB1069) (Scheme 31) 2-chloro-3- and -4-methyquinolines are also subject to methyl chlorinations by similar reagents (91JHC1549). Sulfuryl chloride and NCS are also likely to induce a proportion of lateral chlorination (83KFZ1055 86S835). 

Chlorination. When 75 was treated with chlorine in the presence of aluminium chloride, initial chlorination took place at the 5-position, but the reaction was rather unselective 5,8-di-, 5,7,8-tri-, and 5,6,7,8-tetra-chloroisoquinolines were also formed (64JOC329). Perchlorination has been achieved by initial reaction of the isoquinoline-aluminium chloride complex with chlorine, as above, followed by treatment with phosphorus pentachloride at 270°C in an autoclave [66JCS(C)2328]. Treatment of 1,8-dimethylisoquinoline with NCS gave the 5-chloro derivative (91NKK-1193). Meisenheimer reaction of isoquinoline 2-oxides with phosphoryl chloride gave 1-chloroisoquinoline (84MI2). 

The common hydroxylic chlorinating agents were not particularly successful in transforming the 3-hydroxy derivative of 136 into its 3-chloro derivative. Yields with phosphoryl chloride and dimethylaniline only reached 15% (66JOC265). 

Isoxazolo[4,5-6]pyrazine (176) is resistant to electrophilic halogenation because the potentially reactive site is at the ring junction. The 7-oxide, though, was converted into the 6-chloro derivative of 176 on heating with phosphoryl chloride (73JHC181). 

When the pyrimido[4,5-c]pyridazine (211) was heated with phosphoryl chloride and dimethylaniline 212 was formed (71CPB1849). Some oxo derivatives appear to be resistant to chlorination e.g., the pyrimido [5,4-c]pyridazine derivative (213) would not react (68JHC523). 2- Arylpyrim-ido[4,5-[Pg.337]

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