Cycloisomerization of Dienynes by a Planar-chiral Gold(I) Complex

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Phosphine organocatalysis in the synthesis of natural products and bioactive compounds

International audienceThis review shows that organocatalytic methods based on the use of nucleophilic phosphorus catalysts have been successfully applied as key steps in the formal or total synthesis of complex natural products. These methods also afford suitable tools for the constitution of either focused or diversity-oriented-synthesis inspired libraries of small molecules for biological screening

C-13 NMR analysis as a useful tool for structural assignment of vinyl- and dienyltin derivatives

International audienceDuring the last decade, vinyl- and dienyltin derivatives have been extensively developed and used in organic synthesis. H-1 NMR analysis of these compounds was the first analytical tool employed, together with Sn-119 NMR, for the assignment of the E or Z stereochemistry of vinylstannyl derivatives. In this paper we want to show that C-13 NMR is a powerful tool for structural analysis of vinyl- and dienyltin compounds. Chemical shifts and C-13-Sn119-117 coupling constants are reported for several examples. In all cases described, the (3)J C-13-Sn119-117 values give the most definitive argument for structural assignment. (1)J, (2)J and (3)J C-13-Sn119-117 coupling constants are also reported, along with the alpha, beta, gamma, and delta effects of the stannyl group. When the vinyltin function is functionalized with a heteroatomic substituant, some important changes occur in the chemical shifts and coupling constants. Some examples are given in the alpha-oxygen. -sulfur, -halogen, -silyl, and -tin substituted vinyltin series