Selenides, aryl alkyl synthesis

The methods of synthesis of diaryl and aryl alkyl selenides have been recently reviewed.215 4-Nitro-phenyl methyl selenide was obtained in 93% yield from the reaction of 4-chloronitrobenzene in DMF with a suspension of MeSeLi in THF, prepared from powdered Se and MeLi.216 Other mixed RSeAr selenides were synthesized via alkylation with RI of ArSe resulting from the nucleophilic substitution of unactivated haloarenes ArCl with MeSeLi in DMF at 120 C, followed by MeSe -induced demethyl-ation.217... 

The difficulties encountered in the synthesis of 2-alkyl- and 2-aryl-substituted selenazoles lie principally in the preparation of the corresponding selenoamides. In this respect, a method is worthy of note in which the use of selenoamides is dispensed with. For this, a nitrile, a hydrogen selenide, and an a-halogenoketone are reacted together in the presence of a condensation catalyst. Phosphorus oxychloride, alone or mixed with zinc chloride or phosphorus trichloride, is specially suitable. The yields of the corresponding 2-alkylseIenazoles are up to a maximum of 25%,... 

Alkyl, alkenyl, aryl and acyl radicals can all be used in cyclization reactions. Acyl radicals can be generated by addition of alkyl radicals to carbon monoxide, or more conveniently from acyl selenides, and undergo a variety of radical reactions. A synthesis of the sesquiterpene (—)-kamausallene made use of the radical cyclization from the acyl selenide 69 (4.61). Tris(trimethylsilyl)silane and triethylborane in air were used to promote the reaction, which is highly selective (32 1) in favour of the cis stereoisomer 70, as expected from a chair-tike transition state. Best yields in the cyclization reactions of acyl radicals are found with electron-deficient alkenes, indicating the nucleophilic character of acyl radicals. 

Grieco, P. A. Gilman, S. Nishizawa, M. Organoselenium Chemistry. A Facile One-Step Synthesis of Alkyl Aryl Selenides from Alcohols /. Or. Chem. 1976, 41, 1485-1486. Sharpless, K. B. Young, M. W. Olefin Synthesis. Rate Enhancement of the Elimination of Alkyl Aryl Selenoxides by Electron-Withdrawing Substituents / Or . Chem. 1975, 40, 947-949. 

---