New and efficient chiral selenium electrophiles.

New chiral diselenides were prepared in a few steps from readily available starting materials. The selenium electrophiles generated from these diselenides were used for the efficient stereoselective inter- and intramolecular functionalization of alkenes. The substitution pattern influences the stereoselectivities and protection of the hydroxy moiety in the chiral side chain led to increased selectivities and yields in the selenenylation reactions. An additional substituent in the second ortho position was advantageous as well. Addition products with up to 96% de were obtained. The influence of the nucleophile on the outcome of selenenylations of alkenes was studied to some extent as well.

Chiral Diselenides in the Total Synthesis of (+)-Samin.

Chiral selenium compounds are applied to stoichiometric as well as to catalytic reactions in the synthesis of substituted tetrahydrofuran derivatives: The selenium compound 1 was used in catalytic amounts for a rapid access to chiral diselenide 3. The efficient stereoselective addition to alkene 5 yields product 8 with a selenium functionality as a precursor for an intramolecular radical cyclization. In this way a short total synthesis of (+)-samin (11), a naturally occurring furofuran lignan, was achieved.