Arsonium ylides thermolysis

This method was extended to different diazonium salts and several arsonium ylides (14) were prepared (23, 32). The reaction is greatly facilitated by the presence of copper, copper-bronze, or copper salts. For example, attempts to prepare the bis(carbethoxy)methylene ylide by thermolysis of diethyl diazomalonate in the presence of triphenylarsine without the presence of a catalyst proved abortive, whereas this ylide was obtained in 61% yield if the reactants were heated at 150°C with copper-bronze (32). 

The arsonium ylides are the most synthetically useful of the organoarsenic(V) compounds. Trimethylarsonium methylide and triphenylarsonium benzylide undergo thermolysis under the mild conditions of refluxing benzene, affording the arsine and an olefin. 

SCHEME 6. Proposed mechanism for the thermolysis of arsonium ylides ... 

Such ylides are unstable and react with carbonyl compounds to give both the Wittig product (p. 545) as well as AsPh3 and an epoxide. However, this very reactivity is sometimes an advantage since As ylides often react with carbonyl compounds that are unresponsive to P ylides. Substituted quaternary arsonium compounds are also a useful source of heterocyclic organoarsanes, e.g. thermolysis of 4-(1,7-dibromoheptyl)trimethylarsonium bromide to l-arsabicyclo[3.3.0]octane ... 

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See also in sourсe #XX -- [ , , , ]

See also in sourсe #XX -- [ , , , ]

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