Enamines natural product synthesis, carbon nucleophile

Palladium-phosphine complexes such as Pd [PPh3 ]4 or, most conveniently, Pd(OAc)2 and PPh3 are used. Usually, these telomers are obtained in high yields. Nucleophiles such as water, carboxylic acids, alcohols, phenols, ammonia, amines, enamines, nitroalkanes, and active methylene and methyne compounds participate in telomerization. Also, carbon monoxide and hydrosilanes are involved in the reaction to give telomers. These easily available telomers are trifunctional and extremely useful starting materials for simple synthesis of certain types of natural products. 

The second exanple is a new synthetic approach to the synthesis of nakadomarin A 202 rscheme 20.. 38T To this end, Wnkler and coworkers developed a tandem Pummerer-Michael process.The generation of the activated thionium ion was performed by the elimination of ethanethiol from thioacetal 198. The intermediate 199 showed double reactivity, that is, a nucleophilic position on the furan to perform the Michael addition and the usual electrophilic thionium, which was in fact trapped by the enamine carbon generating tetracyclic product 200. Winkler presented the s)mthesis of a tetracyclic model system and suggested that this reaction sequence can also be applied to the synthesis of the natural product. 

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