Swans reaction

Many of the trihalides of As, Sb and Bi hydrolyse readily but can be handled without great difficulty under anhydrous conditions. AsFs and SbFs are important reagents for converting non-metal chlorides to fluorides. SbFs in particular is valuable for preparing organofluorine compounds (the Swans reaction) ... 

The presence of one or more halogen atoms on a carbon atom a or j to P=0 renders the phosphorus-carbon bond more liable to break under less forcing circumstances. The fragmentation of (2-haloalkyl)phosphonic acids under aqueous conditions (the Conant-Swan reaction) has been known for many years. Conant and coworkers" ", in the early 1920s, reported on the instantaneous fragmentation of the acids 88 and 89 in aqueous NaHCOj into inorganic phosphate, Br and PhCOCH=CHPh. 

Polymers were used to test the intermediacy of a phosphorylated compound in phosphorylations observed during base-promoted decomposition of /3-halo phosphonate (Conant-Swan reaction) (Rebek et al., 1977,1978). Polymer-bound jS-chlorophosphonate was prepared and decomposed in the presence of an amine-bearing polymer of different bead size. It was shown that phosphorylation of the amine-bearing polymer occurred, indicating the intermediacy in solution of a phosphorylating species. 

Initial work by Edgar and Swan [43], Adams and Merz [44], Prideaux [45], Markowitz and Boryta [46], and Carstensen [ 1 ] suggested that the rate of moisture uptake onto water-soluble solids above RH0 should depend on the difference between the partial pressure of water in the environment and that of the partial pressure of water above a saturated solution of a water-soluble substance, temperature, the exposed surface area of the solid, the velocity of movement of the moist air, and a specific reaction constant that is characteristic of the individual solid. 

At the same time the interaction of superoxide with MPO may affect a total superoxide production by phagocytes. Thus, the superoxide adduct of MPO (Compound III) is probably quantitatively formed in PMA-stimulated human neutrophils [223]. Edwards and Swan [224] proposed that superoxide production regulate the respiratory burst of stimulated human neutrophils. It has also been suggested that the interaction of superoxide with HRP, MPO, and LPO resulted in the formation of Compound III by a two-step reaction [225]. Superoxide is able to react relatively rapidly with peroxidases and their catalytic intermediates. For example, the rate constant for reaction of superoxide with Fe(III)MPO is equal to 1.1-2.1 x 1061 mol 1 s 1 [226], and the rate constants for the reactions of Oi and HOO with HRP Compound I are equal to 1.6 x 106 and 2.2 x 1081 mol-1 s-1, respectively [227]. Thus, peroxidases may change their functions, from acting as prooxidant enzymes and the catalysts of free radical processes, and acquire antioxidant catalase properties as shown for HRP [228] and MPO [229]. In this case catalase activity depends on the two-electron oxidation of hydrogen peroxide by Compound I. 

The natural antipode of corynantheine (35, 155, 20/ ) has elegantly been prepared by Autrey and Scullard (168), starting from yohimbone (305), synthesized and resolved previously by Swan (169). Yohimbone (305) was converted to 18-formylyohimbone (306) and then through 307 to oxime 308. On reaction with thionyl chloride, 308 underwent a Beckmann fragmentation to the trans-substituted indolo[2,3-a]quinolizine 310, which after desulfurization and esterification resulted in the levorotatory methyl corynantheate (304). This product... 

The chapter by C. J. Swan and D. L. Trimm, which also emphasizes the effect on catalytic activity of the precise form of a metal complex, shows too that, depending on the metal with which it is associated, the same ligand can act either as a catalyst or inhibitor. The model reaction studied was the liquid-phase oxidation of ethanethiol in alkaline solution, catalyzed by various metal complexes. The rate-determining step appears to be the transfer of electrons from the thiyl anion to the metal cation, and it is shown that some kind of coordination between the metal and the thiol must occur as a prerequisite to the electron transfer reaction (8, 9). In systems where thiyl entities replace the original ligands, quantitative yields of disulfide are obtained. Where no such displacement occurs, however, the oxidation rates vary widely for different metal complexes, and the reaction results in the production not only of disulfide but also of overoxidation and hydrolysis products of the disulfide. 

At the present time, catalytic reactions in supercritical carbon dioxide for the manufacture of fine chemicals appear to be more commercially feasible (McCoy, 1999). A large range of reactions have been investigated in cooperation with the University of Nottingham and Thomas Swan Co., Ltd. (Consett, Co. Durham, U.K.) (Meehan et al., 1999). Very high space-time... 

Satterthwait also has demonstrated that methyl metaphosphate, generated in solution by the Conant-Swan fragmentation, will react with acetophenone in the presence of base to yield the corresponding enol phosphate. When, however, the reaction is carried out in the presence of aniline, the product is the Schiff base. Presumably, the processes take place by the pathways shown by the reactions in Equations 10 and 11. 

A second synthesis of sempervirine was later reported by Swan (96), according to the following reaction sequence. 3-Cyano-5,6,7,8-tetra-hydroisoquinoline reacted with 3-ethoxypropyl magnesium bromide to... 

The A sUgXmu Swan bands of C2 are emitted from several complex reaction systems. The potential curves for C2 [153] are shown in Figure 1.10. 

Palmer and his co-workers have observed more complex C2 emission from diffusion flames of alkali metals (Na or K) in haloforms and carbon tetra-halides [160-165], The Swan bands show a much broader v distribution than those emitted from other systems, and although the v = 6 level is sometimes excited preferentially, it is clear that more than one process excites the A 3I1B state in the diffusion flame reactions. Detailed interpretation is difficult and is hampered by a lack of precise thermochemical data for some of the species involved. Tewanson, Naegeli, and Palmer [165] have suggested that three quite distinct mechanisms may cause excitation (i) the association of C... 

Swan. G. A., Studies of the reaction of benzoyl peroxide with N,N-disubstituted aromatic amines and related compounds. V, J. Chem. Soc. C, 2880, 1971. 

A study of the reaction of cyanogen bromide in 0.3 N HCl with the common amino acids showed that, besides methionine, only cysteine (cf. Swan, 1958), but neither cystine, tyrosine, nor tryptophan, reacted. Cleavage of... 

By use of mixtures of sulfite and a mercurial to form a mercaptide with the thiol (Leach, 1960). The reaction can be considered as displacing the equilibrium by removing the thiol as soon as it is formed or less probably as due to a sulfite-mercurial reactant of increased nucleophilic character (Milligan and Swan, 1962). 

This is merely a formulation, however, and any plausible reaction mechanism seems to involve precisely the same type of difficulties as are associated with the simpler formulation (IV). For example, Milligan and Swan (1961) obtained some evidence that Bunte salts can undergo an exchange reaction with disulfide bonds. They suggest (Milligan and Swan, 1962) that such an exchange mechanism can lead to the reactions. 

Reaction (XIV) is visualized as a direct nucleophilic attack of the thiol anion on the carbon atom holding the SON group (Swan, 1957c Parker and Kharasch, 1959). Earland and Raven (1960, 1961) draw the same conclusions from studies on model compounds. 

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