Zinc tosylate

Sulfonate esters also can be prepared under Mitsunobu conditions. Use of zinc tosylate in place of the carboxylic acid gives a tosylate of inverted configuration. 

Zinc tosylate, (CILCfdLSOjJjZn. The salt is prepared by reaction of tosic acid monohydrate in water with zinc chloride (J. T. Baker). 

Tosylation with inversion.1 The reaction of a secondary alcohol with zinc tosylate, diethyl azodicarboxylate, and triphenylphosphine (Mitsunobu inversion, 5, 728) leads to the inverted tosylate in about 80-95% yield. Lithium tosylate is less effective. The reaction is sensitive to steric hindrance. 

Carboxylate anions derived fi om somewhat stronger acids, such as / -nitrobenzoic acid and chloroacetic acid, seem to be particularly usefixl in this Mitsunobu inversion reaction. Sulfonate esters can also be prepared under Mitsunobu conditions. Use of zinc tosylate in place of the carboxylic acid gives a tosylate of inverted configuration ... 

It is practical to place a washing bottle or scrubber in the gas line just before the manifold. The aqueous solution in this bottle contains a reductant for traces of molecular oxygen and at the same time wets the gas which will minimize a concentrating effect on the sample by drying. A practical solution is 1 mM zinc acetate, 1 pM TMP (meso-tctra(/V-methyl-4-pyridyl)porphinc-tetra-tosylate), 100 mM Na2EDTA, 100 mM Tris-HCl buffer at pH 10. The porphyrin complexates the Zn2+ and forms a light-sensitive compound that can be excited by near UV light from an 18 watt TL-tube. 

Zinc Complexation withp-tosyl-8-aminoquinoline and adsorption on cation exchange resin Spectrofluorimetry 0.1 nM absolute [609]... 

The transmetallation of the lithiated anion, generated from the tosylate of trifluoro-ethanol, is performed at low temperature with a borane or with cyclopentadienylzir-conium. A further transmetallation affords a second organometallic species that is more stable or more reactive (zinc or copper) and that has a broader synthetic potential... 

Zinc(II) chloride, bromide and iodide were found to ring open iV-tosyl-2-phenyla-ziridines forming the tnms-/3-haloamine in a regiospecific reaction at the benzylic carbon of the aziridine ring.51 In the absence of a benzylic carbon, the halide ion attack was mainly at the least substituted carbon of the ring. 

Normally tosyl cyanide reacts with the functionalized zinc reagents, such as 44, to provide the expected nitrile 45 (0°C to 25 °C, 2 h). However, the benzylic zinc reagent 46 and the corresponding copper-zinc reagent 47 react with tosyl cyanide differently. Whilst the zinc reagent furnishes the SE2 substitution product 48 (functionalization at the ortho position of the phenyl ring), the zinc-copper compound leads to the direct (SE2) substitution product 49 (Scheme 1.14).51... 

In the previous subsection, it was shown that the Ferrier reaction offers an opportunity to convert glycal derivatives into unsaturated sugar derivatives, which have an isolated double bond between C(2) and C(3). The Tipson-Cohcn reaction is another important reaction for the introduction of isolated double bonds.29 In this procedure, a cis or tram diols are converted into disulfonates (mesylates or tosylates) which are reductively eliminated with sodium iodide and zinc in refluxing DMF (Scheme 3.6a). In this reaction, the C(3) sulfonate is substituted by an iodide, which then is reductively removed by zinc with concomitant elimination of the second sulfonate moiety, introducing a double bond. Stereoelectronic effects make nucleophilic substitutions at C(3) more favourable than similar reactions at C(2) (see Section 3.2.3). Probably, the elimination proceeds through a boat conformation. In this case, the iodide and tosylate are in a syn relation. In most cases, E2 elimination proceeds via a transition state involving an anti orientation. Nevertheless, syn elimination becomes the dominant mode of reaction when structural features prohibit an anti orientation. 

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