Iodine/zinc displacement

Replacement of sulfonyloxy groups by hydrogen is also achieved by refluxing the methanesulfonyl and p-toluenesulfonyl esters of alcohols with sodium iodide and zinc dust in wet dimethoxyethane. Evidently iodine displaces sulfonyloxy group and is replaced by hydrogen by means of zinc. Yields range from 26% to 65% [700] (Procedure 33, p. 213). 

Immediately upon connecting the cell to a source of direct current, a deposit of gray metallic zinc appears on the surface of the cathode and bubbles of chlorine gas appear at the surface of the anode. A simple chemical test for chlorine may be made by leading this gas into an aqueous sodium iodide solution, whereupon the solution assumes a yellow color caused by displacement of iodine by chlorine. Accordingly, it is concluded that the products of the electrolysis of a zinc chloride solution are elemental zinc and elemental chlorine, and the next problem is that of explaining the mechanism by which these products may be produced. 

In the event, Mitsunobu-type displacement of the unprotected hydroxyl of 24 delivered the iodinated sugar 25, which was then elaborated into acyclic iodohexenitol 26 via ring opening using activated zinc in refluxing ethanol, followed by reduction, tosylation and iodination. The pivotal radical cyclization/oxygenation of 26 was finally carried out in the presence of a catalytic amount of cobalt(salen) complex in air. This... 

Iodine, iron, and zinc increased in wells over the concentrations in the brine or local groundwater, represented by the private (PVT) well. The researchers hypothesized that chemical displacement of ions coating the sand grains took place. This explanation is plausible for the iron alone. Hence, another explanation was... 

A special case of a Negishi coupling was performed with 1-hydroxy-imidazole (92), which could be etherified with Merrifield and Wang resin (91) [210]. Upon treatment with Bull, the H-2 is removed giving a stabilized carbanion, which can react with various electrophiles such as aryl iodides (2). Both ZnCh and Pd(PPh3)4 were required for the reaction. The Z.riCL was used in excess and displaces the Li from the imidazole. The Pd catalyst was added in small quantities (0.1 equiv.) and performs an insertion into the aryl-iodine bond creating the electrophile to be trapped by the zinc imidazolide. Several 2-arylated 1-hydroxyimidazoles (95) were obtained by this method in almost quantitative yields (Scheme 21). 

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