Anions tosylates, also

Halide and Azide Anions. These also open the epoxide re-gioselectively at the C-3 position. Addition of Li2CuBr4 results in bromide addition at the C-3 position of rac-(l), forming 3-bromo-1,2-propane 1-0-tosylate in 70-76% yield in THF or acetonitrile at It, or 1,3-dibromo-2-propanol in 82% yield in refluxing acetonitrile. Hydrofluorination takes place with KHF2 under solid-liquid phase transfer conditions, but the yield of fluorohydrin is very low (eq 3). Azidotrimethylsilane adds in the presence of a Lewis acid catalyst (eq 3). Addition of cyanide ion is achieved by using Diethylaluminum Cyanide in toluene. ... 

Tosylate is displaced by weak oxyanions with little elimination in aprotic solvents, providing alternative routes to polymer-bound esters and aryl ethers. Alkoxides, unfortunately, give significant functional yields of (vinyl)polystyrene under the same conditions. Phosphines and sulfides can also be prepared from the appropriate anions (57), the latter lipophilic enough for phase-transfer catalysis free from poisonning by released tosylate. 

Evidence is presented for continuous tuning of the band-filling between y - 0.00 and 0.50. In comparison, electrochemical oxidation of monoclinic /)-Ni(Pc) under the same conditions is also accompanied by a significant overpotential in forming tetragonal Ni(Pc)-(BF4)0.48- However, electrochemical undoping produces the monoclinic 7-Ni(Pc) phase with far less band structure tunability than in the silicon polymer. Experiments with tosylate as the anion indicate that tetragonal [Si(Pc)0](tosylate)y n can be tuned continuously between y = 0.00 and 0.67. For the anions PFg,... 

We have also seen good leaving groups other than halide ion, e.g. tosylate anion (cf. p. 88),... 

Polyphosphates and phosphates have also been obtained under phase-transfer catalytic conditions by nucleophilic displacement reactions on haloalkanes, tosyl-oxyalkanes and sulphonium salts by polyphosphate or phosphate anions [e.g. 7, 11-15]. The procedure has been used with success for the phosphorylation of terpenes [11] and nucleosides [12, 13]. 

The reduction of tosylhydrazones can also be performed with sodium borodeuteride in boiling methanol or dioxane, but the mechanism of this reaction (in boiling dioxane at least) is radically different from that of the lithium aluminum deuteride reductions.82 With sodium borohydride the first step is apparently hydride attack on the carbon atom of the C=N bond which is probably concerted with the elimination of the tosylate anion (110 - 111). Migration of the hydrogen from nitrogen to C-3 in (111) concerted with expulsion of nitrogen, provides the corresponding methylene derivative (100).82... 

The epoxide evidently could not be used as the leaving group for the cyclisation so it was opened with benzyloxide anion 48 and activated by tosylation 49. After deprotection, enolate cyclisation gave 50 from which copaene was made. There are two possible enolates from 49 the other would also give a four-membered ring if it cyclised but it is too far away. 

When steric hindrance in substrates is increased, and when the leaving anion group in substrates is iodide, SET reaction is much induced (Cl < Br < I). This reason comes from the fact that steric hindrance retards the direct nucleophilic reduction of substrates by a hydride species, and the a energy level of C-I bond in substrates is lower than that of C-Br or C-Cl bond. Therefore, metal hydride reduction of alkyl chlorides, bromides, and tosylates generally proceeds mainly via a polar pathway, i.e. SN2. Since LUMO energy level in aromatic halides is lower than that of aliphatic halides, SET reaction in aromatic halides is induced not only in aromatic iodides but also in aromatic bromides. Eq. 9.2 shows reductive cyclization of o-bromophenyl allyl ether (4) via an sp2 carbon-centered radical with LiAlH4. 

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