Phosphorus, nucleophilic displacement reactions

Benzazepin-2-amines can be obtained by nucleophilic displacement reactions on a variety of substrates. For example, the benzazepin-2-amine 22 is formed by treating the thiolactam 21, obtained from the benzazepinone 20 with phosphorus pentasulfide in pyridine or triethylamine solution, with ammonia.61... 

Michalski, M., Mikolajczyk, M., and Omelanczuk, ]., Stereochemistry of nucleophilic displacement reaction at thiophosphoryl centre. An example of the Walden cycle involving phosphorus, Tetrahedron Lett., 1779, 1965. 

Pyridyl-phosphorus and -arsenic compounds have also been made by nucleophilic displacement reactions with, for example, 3-pyridinediazonium salts (74HC(14-2)489). Organomercury derivatives can be converted into bromides and iodides by standard methods, e.g. Scheme 147 (59JPR(8)156). 

Pyrimido[4,5-d]pyrimidine derivatives undergo a wide variety of nucleophilic displacement reactions. Pyrimido[4,5-d]pyrimidin-4-ones are readily chlorinated in either phosphorus oxychloride (62JOC4211) or a mixture of phosphorus pentachloride and thionyl chloride (74JMC451) to give the corresponding 4-chloropyrimido[4,5-d]pyrimidines. These chloro compounds are generally not purified but are isolated crude and used for subsequent nucleophilic displacements. 

This type of map can be used to discuss the different types of nucleophilic displacement reaction. Using the simplified version shown in Fig. 2 we have already seen that SN1 reactions, for instance the solvolysis of triarylmethyl halides, go through the separated ions in the top right-hand corner (Swain et al., 1953 Ritchie, 1971). At the opposite extreme, nucleophilic substitution at centres where the number of ligands can be increased may proceed over the bottom left-hand corner of the diagram. Examples are acyl transfer reactions and substitution at tetrahedral phosphorus centres (Alder et al., 1971) as well as substitution at square planar transition metal compounds (Wilkins, 1974). The nucleophilic reactions studied by Ritchie (1976), for which the rate... 

K. D. Berlin, T. H. Austin, M. E. Peterson u. M. Nagabhushanam, Nucleophilic Displacement Reactions on Phosphorus Halides and Esters by Grignard and Lithium Reagents, Topics in Phosphorus Chemistry 1, 17 (1974). 

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. 

The cyclic phosphinate (96) has been isolated from the reaction of dichloro(methyl)phosphine with the ethoxycarbonylimine derived from hexafluoroacetone. Treatment of trichloro(organo)phosphonium-hexafluorophosphate salts with dichloro(diethylamino)phosphine results in the halophosphonium salts (97). Some reactions of dichloro(-)menthylphosphine have been reported.As usual, nucleophilic displacement reactions of halogenophosphines have received attention as routes to new systems of interest as ligands.Of particular interest in this connection is a report of the synthesis of the phosphorus-functionalised calixarenes (98). Only one chlorine atom of dichloro(phenyl)-phosphine is replaced on treatment with an excess of dicyclohexylamine, enabling the stepwise synthesis of the chiral aminophosphines (99), described as air-stable solids. 

The reactions of P-halophospha-alkenes with carbenes provide a new route to 1-chloro-lH-phosphirines (181). Such compounds are highly reactive, and a study of nucleophilic displacement reactions at phosphorus has been facilitated by preparation of the related P-W(CO)5 complexes.The first pentacoordinate systems derived from phosphirenes, (182), have been formed in the reactions of P-halo- or P-cyano-phosphirenes with tetrachloro-o-quinone. Evidence has been presented for the rearrangement of P-chlorophosphirenium ions (183) to the vinylphosphenium ions (184)... 

A study of the reaction of N-arylhydrazides (74ab) with phosphorus pentachloride depends upon the molar ratio of the reactants and may lead to either the monocyclic phosphoranes (75ab) or spirophosphoranes (76ab) in which the P-Cl bonds may undergo a number of nucleophilic displacement reactions (e.g. by alcohols). ... 

Amino, alkoxy, and aryloxy polyphosphazenes are typically prepared by nucleophilic displacement reactions of poly(dihalophosphazenes). Analogous reactions with organometallic reagents, however, result in chain degradation and cross linking rather than in linear, alkyl, or aryl substituted poly(phosphazenes). The thermolysis of appropriate silicon-nitrogen-phosphorus compounds can be used to prepare fully P—C bonded poly(organophosphazenes). The synthesis of two of these materials and their Si—N—P precursors is described here. 

Examples of other nucleophilic displacement reactions at tetracoordinate phosphorus, which proceed with retention of configuration and which involve systems possessing the necessary steric and electronic criteria for stereochemical analysis along the lines discussed above, include the alcoholysis and aminolysis of four-membered ring phosphinates and phosphinyl chlorides, respectively, and the HSiCh/triethylamine reduction of 17B Similar analysis of the base-catalyzed hydrolysis of 25 and 26 which, in contrast to the hydrolysis of acyclic analogsproceed with retention... 

In conclusion, we may expect further advances in understanding factors controlling structural and conformational preferences of cyclic oxyphosphoranes, both from an experimental as well as a theoretical point of view. As the area continues to develop, the use of oxyphosphoranes as models in mechanistic interpretation should enhance our understanding of pathways followed in nucleophilic displacement reactions of tetracoordinated phosphorus compounds. Acknowledgment... 

Berlin, K.D., Austin, T.H., Peterson, M., and Nagabhushanam, M., Nucleophilic displacement reactions on phosphorus halides and esters by Grignard and lithium reagents, in Topics in Phosphorus Chemistry, Vol. 1, John Wiley Sons, New York, 1964, pp. 17-56. 

A novel procedure has been developed for the synthesis of phosphate esters of hindered alcohols, and was designed to avoid nucleophilic displacement reactions. It involves photolysis of the alkyl nitrite in the presence of a trialkyl phosphite and proceeds by addition of the alkoxyl radical to phosphorus followed by elimination of an alkyl group (Scheme 3). ... 

Nucleophilic Displacement Reactions on Phosphorus Halides and Esters by Grignard and Lithium Reagents... 

The purpose of the remaining discussion in this section is to review further developments in the chemistry of nucleophilic displacement reactions at phosphorus in the P=Z bond (Z = O, S or Se) as pertinent to phosphonic and phosphinic derivatives. 

K.D. Berlin et al.. Nucleophilic displacement reactions on phosphorus halides and esters-, Topics... 

A representation of some nucleophilic displacement reactions utilizing bromoethane (ethyl bromide, CH3CH2Br) as a prototypical primary alkyl substrate upon which the various nucleophiles act. The display of synthetic versatility in the Sn2 reaction producing the many varieties of compounds illustrates carbon-oxygen, carbon-sulfur, carbon-nitrogen, carbon-phosphorus, and carbon-carbon bond formation and should not be taken to exclude other possibilities. The details of the conditions might be specified as in Table 7.4 for each case but are omitted here for brevity. 

Nagelkerke, R., Thatcher, G.R.J., Buncel, E. Alkali-metal ion catalysis in nucleophilic displacement reactions at carbon, phosphorus, and sulfur centers. IX. p-Nitrophenyl diphenyl phosphate. Org. Biomol. Chem. 2003,1, 163-167. 

---