Highly regio- and stereoselective Heck reaction of allylic esters with arenediazonium salts: application to the synthesis of kavalactones.

A highly efficient palladium-catalyzed Heck reaction of allylic esters with arenediazonium salts is described. The reaction proceeds under mild conditions, with excellent to total regio- and stereochemical control and with retention of the traditional leaving group. Furthermore, the generality of the present methodology is illustrated by the short total synthesis of the natural kavalactones, yangonine, (+/-)-methysticin, and (+/-)-dihydromethysticin.

Highly stereoselective one-pot procedure to prepare bis- and tris-chalcogenide alkenes via addition of disulfides and diselenides to terminal alkynes.

We present here the reaction of diorganoyl dichalcogenides with terminal alkynes under catalyst-free conditions, by a one-pot procedure, to prepare bis- and tris-chalcogenide alkenes selectively, avoiding the previous preparation of chalcogen alkynes. The reaction proceeded cleanly under mild reaction conditions, and the addition of dichalcogenides to alkynes occurred stereoselectively to give exclusively the corresponding Z isomers. We observed that the selectivity control was governed by the effective participation of the hydroxyl group from propargyl alcohols. In addition, the bis-chalcogenide alkenes were exclusively obtained with propargyl alcohol having the acidic hydroxyl group proton. Conversely, the alkynes with no potentially acidic hydroxyl group proton, at propargyl positions, gave exclusively the tris-chalcogenide alkenes.

Protective effect of diphenyl diselenide on acute liver damage induced by 2-nitropropane in rats.

The effect of diphenyl diselenide, (PhSe)2, administration on 2-nitropropane (2-NP)-induced hepatic damage was examined in male rats. Rats were pre-treated with a single dose of diphenyl diselenide (10, 50 or 100 micromol/kg). Afterward, they received only one dose of 2-NP (100 mg/kg body weight dissolved in olive oil). The parameters that indicate tissue damage such as plasma alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transferase (GGT), alpha-fetoprotein (AFP), creatinine and urea were determined. Since toxicity induced by 2-NP is related to oxidative stress, lipid peroxidation was also evaluated. Diphenyl diselenide (100 micromol/kg) significantly reduced plasma ALT, gamma-GGT, AFP levels when compared to 2-NP group. Treatment with diphenyl diselenide, at all doses, effectively protects the increase of lipid peroxidation when compared to 2-NP group. Histological examination revealed that 2-NP treatment causes a moderate swelling and degenerative alterations on hepatocytes and diphenyl diselenide (100 micromol/kg) protects against these alterations. Diphenyl diselenide (50 and 100 micromol/kg) significantly decreased the urea level. This study evidences the protective effect of diphenyl diselenide by 2-NP-induced acute hepatic damage.

Hydrotelluration of aminoalkynes.

Metal tellurolates (M = B3+; BuTeTeBu/NaBH4/EtOH; Li3+, Te0/BuLi/THF; In3+, BuTeTeBu/InI/EtOH) react with aminoalkynes to produce vinylic tellurides containing amino groups; the regio-, and stereo-chemistry of the hydrotelluration reaction depend on the metallic counter ion and on the nature of the amino group substituent.