Raney nickel oxiranes

Aziridines, like oxiranes, undergo hydrogenolysis easily with or without inversion of configuration, depending on the catalyst, reaction parameters, and various additives 65aJ08). For example, hydrogenolysis of 2-methyl-2-phenylaziridine in ethanol occurs mainly with inversion over palladium but with retention over platinum, Raney nickel, or Raney cobalt. Benzene solvent or alkali favor retention over palladium as well. 

Oxiranes react with a wide variety of nucleophilic reagents, under neutral or base- or acid-catalyzed conditions, and this property has led to their extensive exploitation in synthesis. They also undergo hydrogenation in the presence of Raney nickel catalyst, which,... 

General Comments. The formation of deoxy sugars by hydrogenation over Raney nickel often leads to the abnormal isomer (namely, that formed by diequatorial opening of the oxirane ring) as the major product, in contrast to the product afforded by lithium aluminum hydride this suggests that a different mechanism is involved in the nickel-catalyzed reaction. 

Diazocyclopropane converts the 16-bromo-17-oxo-compounds (174) into isomeric spiro-oxirans (175) rearrangement with boron trifluoride gave the corresponding spirocyclobutanones (176), which could be debrominated with Raney nickel."°°... 

An alternative method for synthesis of the 1,6-anhydrides of amino-deoxyhexoses consists in cleavage of the oxirane ring by azide ions in aqueous ethanol or 2-ethoxyethanol in the presence of ammonium chloride as a buffer379-537-539 740-741-750-751 (see also, Ref. 45a). The azido-hydrins thus formed are reduced by nascent hydrogen (from, for example, zinc and hydrochloric acid), or catalytically in the presence of platinum, palladium, or Raney nickel, to give the corresponding amino derivatives. 

Oxirane werden mit Platinmetallen (Pt und Pd) sehr haufig in Gegenwart katalytischer Mengen starker Sauren unter milden Bedingungen, mit Raney-Nickel dagegen meist bei hoheren Temperaturen und Drucken zu Alkoholen hydrogenolysiert (s. ds. Handb., Bd. VI/3, S. 442, sowie Bd. Vl/laTeil 1 S. 338). So erhalt manz. B. aus 3,4-Epoxy-l-me-thyl-4-phenyl-piperidin mit Platin cis-3-Hydroxy-l-methyl-4-phenyl-piperidin (81% d.Th.)3 ... 

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