Preparation sodium phenylselenide

Diethyl l-(phenylseleno)- and l-(phenyltelluro)methylphosphonates " have been prepared in 77-92% yields by the reaction of diethyl iodomethylphosphonate with sodium phenylselenide and lithium phenylteUuride, respectively. 

A convenient and high yielding carbonyl homologation involves the reaction of excess sodium phenylselenide with a phenyl-sulphinyl epoxide. The required epoxides are most easily prepared by the reaction of the anion of an a-chloro-sulphoxide with a ketone and ring closure of the resulting chlorohydrin with potassium hydroxide (equation 12). 

Sodium phenylselenide was prepared in 1 h by sonolysis of diphenyl-diselenide with sodium in the presence of benzopheneone, which acts as an electron transfer agent (Scheme 110) [107]. The reaction between diphenyl-diselenide and solid sodium is virtually negligible at room temperature. However, initial studies showed that the reaction could be brought to completion within four days in the presence of ultrasound. A brief investigation of the effect of solvent on the reaction was carried out in line with those described by Luche and co-workers [83]. Thus it was discovered that the reaction time could be halved by using xylene in place of THF. However, from a practical point of view, the difference in boiling points between that of xylene and THF is considerable. This would severely restrict the applicability of the method as isolation of volatile or thermally unstable selenides would be virtually impossible. 

New methods for preparing known selenium reagents are always interesting. For example, phenyl selenocyanate is readily prepared by addition of trimethyl-silylcyanide to phenylselenyl chloride. Two new preparations of sodium phenylselenide have also appeared. In the first, selenide ion is photolysed in the presence of iodobenzene, whereas the second preparation involves... 

An alternative to azidonitration has recently been reported (Czemecki and Ayadi 1995). Glycal 10.43 reacted with (diacetoxydiodo)benzene PhI(OAc)2, sodium azide, and diphenyldiselenide PhSeSePh, in dichloromethane solution at room temperature gives the cyrstalline azido phenylselenide 10.46 as the only product in 92% yield. Hydrolysis with N-iodosuccinimide then gives hemiketal 10.47 (87%). A few modifications allow the preparation of analogues with a benzyl protection. These hemiketals may be activated by conversion to imidates. 

Selenides eliminate readily without a base. They are generally prepared from enolate anions by reaction with diphenyldiselenide or phenylselenyl bromide to give phenylselenides. The phenylselenides are oxidized with sodium periodate, hydrogen peroxide, or peracids to the selenoxides, which eliminate even at room temperature to afford the a,p-unsamrated ketones and esters [107]. 

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