[Song, Zhen-Lei] Sichuan Univ, Key Lab Drug Targeting, Educ Minist, Dept Med Chem,W China Sch Pharm, Chengdu 610041, Peoples R China

Semipinacol rearrangement in natural product synthesis.

The chemistry of higher order organocuprates

This chapter focuses on the application of tellurium (Te) compounds as reducing reagents of organic substrates Inorganic species—such as hydrogen telluride, sodium hydrogen telluride, sodium telluride—and organic derivatives—such as aryltellurols (and tellurolates) and diorganyl tellurides—are widely employed in several reduction processes—such as reduction of carbonyl compounds, nitro derivatives, epoxides, aryl alkenes, and arylalkynes—as well as in the reductive cleavage of several types of carbon–heteroatom bonds In several cases, the use of Te reagents is clearly advantageous compared to the usual methods because of the mildness of the experimental conditions and the great selectivity The first reported radical reaction promoted by Te reagent was probably the conversion of allylic halides into coupled 1,5-dienes by treatment with telluride anions The reaction, which gives the best results when employing the reagent prepared in situ from elemental Te and lithium triethylborohydride, proceeds through the intermediacy of the thermally unstable bis-allylic telluride, followed by the extrusion of Te and coupling of the formed allylic radicals Additional advantages are the possibility of generating the reducing agents in situ as well in catalytic amounts in the presence of an inexpensive coreductant and the recovery of the Te material

Tellurium in Organic Synthesis

Advances in organic tellurium chemistry

Two general methods for the preparation of β-silyl-substituted divinyl ketones have been developed starting from either α, β-unsaturated aldehydes or simple ketones. Anhydrous FeCl3 induces the cyclization to cyclopentenones under mild conditions and in good yields with predictable and complete control over the position of the double bond in the five-membered ring. The observed effects of substituents on rate can be explained by a rate-determining cationic electrocyclization. Silyl substitution has been shown to retard the reaction.

Eric G. DelMar

Papers

Synthesis of sesqui terpene anti tumor lactones 9. the hydro naphthalene route to pseudo guaianes total synthesis of racemic confertin

Synthesis of sesquiterpene antitumor lactones. 9. The hydronaphthalene route to pseudoguaianes. Total synthesis of (.+-.)-confertin