Halides phosphoryl

Phosphoryl chloride is useful for some dehydrations such as (12.286) and (12.287). Friedel-Krafts reactions are catalysed by POCl3/ZnCl2 mixtures. Preparation of esters is another nse (12.288). The Vilsmeier reaction [12,13] is catalysed by POCI3 (12.289). 

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Chloro- and 5-bromo-isoxazoles have been prepared by reaction of 5-isoxazolones with the appropriate phosphoryl halide (77JMC934). 3-Phenyl-5-trifluoromethylisoxazole has been synthesized by reaction of benzonitrile iV-oxide with 3,3,3-trifluoropropyne (77JMC934). 

The stable molecular nitrosyl halides NOX (p. 442) and phosphoryl halides POX3 (p. 501) find few counterparts in the chemistry of As, Sb and Bi. AsOF has been reported as a product of the reaction of AS4O6 with ASF3 in a sealed tube at 320° but has not been fully characterized. ASOF3 is known only as a polymer. Again, just as AsClj eluded preparation for over 140 y after Liebig s first attempt to make it in 1834, so... 

Acid, sulfonyl, or phosphoryl halides Michael acceptors... 

Aminopyridines and the lactone (43) in polyphosphoric acid at 160 C gave 3-(2-hydroxyethyl)-4-oxo-4//-pyrido[l,2-a]pyrimidines (44). At lower temperature (120 C) the furan derivative (46) was formed.65 When effected with phosphoryl halides (POCl3 or POBr3), reaction of 2-aminopyridines and 43 afforded products of type 44 where the hydroxyl group was replaced by a halogen atom.49-83,85... 

Phosphine oxides R = alkyl, aryl Phosphoryl halides R = Hal... 

The most important oxo halides are the phosphoryl halides (X3PO), in which X may be F, Cl, Br, or I. The commonest (Cl3PO) is obtained by the reactions... 

All X3PO molecules have a pyramidal PX3 group, with the oxygen atom occupying the fourth position to complete a distorted tetrahedron. The P—O bond lengths are about 1.55 A, consistent with the existence of double bonds. Several mixed phosphoryl halides, phosphoryl pseudohalides, as well as X3PS and X3PSe compounds are also known. All of these compounds are prone to ready hydrolysis. 

Primary and secondary phosphines are prepared by LiAlH reduction of organo-phosphorus acids, or esters " Reactions of phosphoryl halides are described in 1.5.5.2.1. Phosphinic acids ... 

In contrast, the reactions of iododiorganophosphines with cyclic ethers lead to the related phosphoryl halide and an alkene... 

A 31P NMR study of the reactions of phosphoryl halides and 4-(dimethyl-amino)phosphine (DMAP) shows the formation of (DMAP)POX2+, (DMAP)-P02X (X = Cl, Br), to give (DMAP)2P02+ and PX5 as final products.1180... 

No solvent was used, and typically the reaction mixture was heated to 150— 200 °C Oower when R = Alkyl), when the phosphoryl halide distilled off, leaving the nitrile in 50— 90% yield. 

The phosphoryl halides (POX3) have a slightly distorted tetrahedral structure, with XPX bond angles of approximately 103°. 

Reaction of 3-substituted indoles with halogens can be more complex initial 3-halogenation occurs generating a 3-halo-3//-indole, ° but the actual products obtained then depend upon the reaction conditions, solvent etc. Thus, nucleophiles can add at C-2 in the intermediate 3-halo-3//-indoles when, after loss of hydrogen halide, a 2-substituted indole is obtained as final product, for example in aqueous solvents, water addition produces oxindoles (20.13.1) comparable methanol addition gives 2-methoxyindoles. 2-Bromination of 3-substituted indoles can be carried ont nsing A -bromosuccinimide in the absence of radical initiators. 2-Bromo- and 2-iodo-indoles can be prepared very efficiently via a-lithiation (20.5.1). 2-Halo-indoles are also available from the reaction of oxindoles with phosphoryl halides. Some 2,3-diiodo-indoles can be obtained by iodination of the indol-2-ylcarboxyfic acid. ... 

Halopyrido[2,3-(/]pyrimidines suitable for nucleophilic exchange reactions are accessible by the conversion of the corresponding pyridone or pyrimidone functions with halogenating agents such as phosphoryl halides or phosphorus pentachloride (see Section 7.2.2.1.1.5.5.). 

Most assuredly the conversion of phosphoryl halides to tertiary phosphine oxides in ether does not consistently provide good yields. In contrast to the situation with phosphorus trihalide, however, the displacement sequence with phosphoryl trihalides can be of preparative value for the intermediate phosphinic halides. 

Closely related to the alkyl exchange reaction is the well-known formation of pyrophosphate esters from the interaction of pentavalent phosphorus esters with phosphoryl halides (296). 

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